JP4504664B2 - Electrostatic discharge protection element and electrostatic discharge protection circuit - Google Patents

Description

The present invention relates to an on-chip electrostatic discharge protection element that is provided on a chip and protects an internal circuit from electrostatic discharge, and more particularly, a thyristor (Silicon-Controlled Rectifier: hereinafter referred to as SCR) type electrostatic discharge protection with an increased turn-on speed. The present invention relates to an element and an electrostatic discharge protection circuit .

  Recently, since semiconductor devices have become more complex and higher in density, there has been a problem that semiconductor devices are destroyed by electrostatic discharge (ESD) during assembly processes in the manufacturing process. As a countermeasure, an on-chip electrostatic discharge protection element (hereinafter also referred to as an ESD protection element) that protects internal circuit elements by efficiently discharging an electrostatic discharge current through a safe path is provided in a semiconductor device chip. It has been.

  In particular, in the case of a CMOS transistor chip, miniaturization has progressed and the gate oxide film has become extremely thin, and the withstand voltage of the gate oxide film has decreased, so that it becomes extremely sensitive to ESD discharge. Yes. In other words, the difference between the voltage (trigger voltage) at which the electrostatic discharge protection element starts to become low impedance and the withstand voltage of the gate oxide film is getting smaller. There is an increased risk of breakdown when voltage is applied. Therefore, recent electrostatic discharge protection elements are required to lower the trigger voltage together with the clamp voltage as the withstand voltage of the gate oxide film decreases.

  In general, an input circuit of a CMOS transistor circuit that requires high-speed operation requires a low RC delay, and therefore, it is necessary to reduce an additional capacitance by adding an electrostatic discharge protection circuit. You cannot use a large protective resistance. In addition to the additional capacity, it is also required to reduce the layout area of the protection element from the viewpoint of manufacturing cost.

  In particular, a method for protecting a chip from damage caused by an ESD phenomenon using SCR has a very low capacity, a small layout area, and a very low holding voltage compared to other protection elements. It has been used extensively because of its excellent advantages. This SCR type electrostatic discharge protection element is described in Patent Documents 1 to 3 and Non-Patent Document 1.

27 is a plan view showing a layout of a low voltage trigger SCR which is an electrostatic discharge protection element of Conventional Example 1, and FIG. 28 is a cross-sectional view taken along line AA shown in FIG. As shown in FIGS. 27 and 28, in the electrostatic discharge protection element of Conventional Example 1, the first P well 3a, the N well 2 and the second P well 3b are formed on the surface of the P ⁺ semiconductor substrate 1. In the region of the N well 2 partitioned by the element isolation insulating film 6, a P ⁺ region 4 serving as an SCR anode and an N ⁺ region 5 serving as an N well potential fixing electrode are formed. A pair of N ⁺ regions 9 serving as the source and drain of an NMOS transistor are formed in a P well 3 b adjacent to the well 2, and a gate electrode 8 is formed on the substrate between the N ⁺ regions 9. Further, in this N ⁺ region 9, the drain portion of the NMOS transistor (N ⁺ region 9 on the P ⁺ region 4 side) is connected to the N well 2, and the source portion (N ⁺ region on the opposite side) of the NMOS transistor. 9) is the cathode of the SCR.

The input pad is connected to an input signal, a power supply line and the like together with the N ⁺ region 5 of the N well potential fixing electrode. The ground pad is connected to the N ⁺ region 9 that becomes the cathode of the SCR. Reference numeral 7 denotes a P ⁺ region for preventing latch-up, which is connected to the ground and serves as a guard ring. In FIG. 24, only a part of the guard ring is shown.

When positive overvoltage static electricity is applied to the input pad connected to the SCR, the drain side PN junction of the NMOS transistor causes an avalanche breakdown, and the MOS transistor passes a hole current toward the P ⁺ guard ring via the substrate. As a result, the substrate potential is raised. This raises the potential of the bottom surface of the cathode of the SCR (source of the NMOS transistor), causing the N ⁺ / P diode to be forward biased and causing the lateral NPN bipolar element 11 to conduct. Further, when a current flows in the N well 2, a potential difference is generated in the N well 2, and the potential on the bottom surface of the anode (P ⁺ region 4 in the N well 2) is the N well constituting the N well potential fixing electrode. ^By lowering compared to the potential of the ⁺ region 5, the P ⁺ / N diode is forward-biased and the vertical PNP bipolar element 12 becomes conductive. At this time, since the vertical bipolar element 12 supplies a current to the substrate, positive feedback that promotes the conduction of the horizontal bipolar element 11 occurs. Therefore, a low-resistance current path is formed between the anode (P ⁺ region 4) and the cathode (N ⁺ region 9) within a time of about 1 nanosecond. During this protection operation, the turn-on impedance is extremely low, so that even when a large current flows, the clamp voltage is very low. Therefore, the SCR of Conventional Example 1 is called a low voltage trigger SCR. As described above, the SCR can be said to be an ideal electrostatic discharge protection element because it can generally suppress power consumption and has a high breakdown current and a low clamp voltage.

  FIG. 29 is a graph comparing the characteristics of various SCRs with voltage on the horizontal axis and current on the vertical axis. In the SCR, when the trigger current is exceeded, a latch operation occurs, a low-resistance current path is generated, and the voltage is lowered. This phenomenon is generally referred to as snapping back. As shown in FIG. 29, the trigger current of a general SCR such as the low voltage trigger SCR of the above-described conventional example 1 is as extremely low as 1 to 10 mA. Also, the minimum current value (holding current) that can hold the SCR operation is as low as 10 to 100 mA, and the minimum voltage (holding voltage) during the SCR operation is usually very low, about 1V. Furthermore, since the dynamic resistance is 1 to 2Ω, which is lower than that of the MOS type ESD protection element, it is possible to prevent an excessive voltage from being applied to the protected element when a surge current flows. Furthermore, since the breakdown current of the SCR itself is high, the overall protection performance is superior to other protection elements.

  Note that the protection performance of the SCR, that is, the transition time until the holding voltage, dynamic resistance, and low resistance depend on the anode-cathode interval. In order to make a high-performance SCR that operates at high speed, the interval is used. Although there is a document describing that it is necessary to minimize the width of the NPN bipolar transistor 11 in practice, it is often pointed out that the performance of the SCR is determined because the performance of the lateral NPN bipolar transistor 11 is low.

  From this point of view, the low voltage trigger SCR often cannot be narrowed between the N well and the cathode, and the transition time may be extremely long. Therefore, it is considered that the ESD protection performance is greatly deteriorated.

  The circuit for supplying the triggering current is not limited to the circuit of the conventional example 1, but may be a circuit in which a current starts to flow when a certain voltage is exceeded, and there is a circuit in which a diode is connected in series.

30 is a plan view showing the layout of the electrostatic discharge protection element described in Patent Document 4, and FIG. 31 is a cross-sectional view taken along the line BB shown in FIG. In this electrostatic discharge protection element, a P ⁺ region 10 that directly serves as a trigger tap is formed in the second P well 3b in place of the NMOS transistor. The substrate potential is raised by supplying the trigger current from the P ⁺ region 10. As a circuit for supplying a substrate current, an N-type MOSFET is used, and a circuit connecting a source and a P ⁺ region is a substrate bias circuit. Further, regarding the SCR trigger method, Patent Documents 8 and 10 describe a method for supplying a current to the N-well 2. 32 is a cross-sectional view showing the electrostatic discharge protection element described in Patent Document 10, and FIG. 33 is a cross-sectional view showing the electrostatic discharge protection element described in Patent Document 8. As shown in FIG. 32, the electrostatic discharge protection element described in Patent Document 10 is formed with a PN diode with an anode electrode 4 in an N well region 2 and connected to a trigger circuit. This is called a V-PNP trigger SCR. In addition, as shown in FIG. 33, the electrostatic discharge protection element described in Patent Document 8 has a trigger tap (N ⁺ layer 5b and P ⁺ layer 10) disposed between the anode and the cathode, and the trigger tap is mutually connected. Current is supplied to speed up the trigger operation.

  Furthermore, in the conventional electrostatic protection element, as described in FIG. 2a of Patent Document 5, FIG. 8 of Patent Document 6, Non-Patent Document 1, and the above description, when the power supply voltage is low, Since the holding voltage of the SCR may be latched up during normal operation, a resistance element is added to the potential fixing electrode of the substrate or the N well as shown in FIG. The circuit configuration can be adjusted. These are generally called holding voltage adjustment type SCRs. This holding voltage adjustment type SCR can increase the minimum current value (holding current) for maintaining the SCR operation by setting the base resistance of each bipolar element constituting the SCR small. As shown in FIG. 29, when the holding current is determined from the IV characteristics of the SCR, the holding voltage is determined correspondingly.

  However, in order to be able to adjust the holding voltage with an external resistor, in such a circuit configuration, it is necessary to sufficiently reduce the N well resistance and the P well resistance provided in the SCR structure. In an SCR using a high resistance substrate or an SCR using an STI (Shallow Trench Isolation) process, the resistance value cannot be lowered, so that it has been difficult to realize. In view of this point, Patent Document 7 and Patent Document 9 which is an invention of the inventors of the present application describe a layout that lowers the P-well resistance and the N-well resistance.

  Patent Document 7 and Non-Patent Document 3 disclose an electrostatic discharge that improves the trigger method described in Patent Document 4 and enables a method of adjusting the holding voltage, which is a problem of Patent Documents 5 and 6, with an external resistor. An SCR that is a protective element is described. These are also called HHI-SCRs, but follow the concept of the holding voltage adjustment type SCR. 35 is a plan view showing the layout of the SCR described in Patent Document 7, FIG. 36 (a) is a cross-sectional view taken along line CC shown in FIG. 35, and FIG. 36 (b) is a diagram shown in FIG. It is sectional drawing by -D line. As shown in FIGS. 35, 36 (a) and 36 (b), the SCR described in Patent Document 7 is divided into an anode and a cathode, and an N-well potential control electrode and a P-well potential control electrode are interposed therebetween. Inserting. That is, with this structure, the effective N-well resistance and P-well resistance can be reduced.

In Non-Patent Document 3, an effective N-well resistance is adjusted by changing the number of connections between the N-well potential control electrode and the input terminal in the N-well, and two resistance values of the external resistance are set. There is a description that the holding voltage is adjusted in combination. This external resistance value is set and adjusted such as changing the number of connections between the N-well potential control electrode and the input terminal in the N-well with a target of a low value (for example, about 2 to 10Ω) in advance. I do. During the trigger operation of the SCR, a current is supplied to a parallel circuit of a resistance element and a PN diode (including a P-well resistor) between the P-well potential control electrode 7 and the cathode 9. Since the trigger current is supplied to the P ⁺ region between the cathodes, it is assumed that the trigger is efficiently applied. Actually, Patent Document 7 and Non-Patent Document 3 describe that most of the current is shunted to the resistance element because the resistance value of the P-well / N ⁺ diode is low.

  In the SCR described in Non-Patent Document 3 and Patent Document 7, NMOS is used as a trigger element (trigger current supply element). For this reason, until the SCR becomes low resistance, the trigger element discharges current through the resistance element, so that its IV characteristic is similar to that of NMOS. In the holding voltage adjustment type SCR, both the trigger current and the holding current can be set to extremely high values and controlled as compared with the normal SCR. Further, as detailed characteristics are described in Non-Patent Document 3, this SCR has a sufficiently low trigger voltage.

FIG. 37 is a sectional view showing another embodiment of the electrostatic discharge protection element of Patent Document 7. In FIG. As shown in FIG. 37, in Patent Document 7, as another example, two trigger elements are connected to an N well potential control electrode 5 and a P well potential control electrode 7 respectively, and each trigger circuit is connected to each resistance element. There is a description on a method of triggering the SCR at two locations by supplying a current from. As shown in FIG. 37, when the substrate trigger method is applied to the holding voltage control type SCR, a resistance element is connected between the P-well potential control electrode 7 and the ground terminal. During the trigger operation of the SCR, a current is supplied to a circuit that enters the resistance element and the P well / N ⁺ diode (including the P well resistance) between the P well control electrode and the cathode. In a normal structure, since the resistance value of the P-well / N ⁺ diode is high, most of the current is shunted to the resistance element. Therefore, the clamp voltage is determined by the resistance value of the resistance element between the P-well potential control electrode 7 and the ground element. Therefore, the resistance value is set in advance with a target of a low value.

  Furthermore, Patent Document 11 describes a method for controlling the holding voltage and the trigger voltage by applying “a triggering voltage adapter network and a holding voltage adapter network” to the low voltage trigger SCR. Furthermore, Patent Document 12 describes that element isolation used for SCR is not STI, but a normal MOS-like structure is used for element isolation to increase the current amplification factor of each bipolar element. is there. Note that these element isolation structures are described in FIGS. 2A and 2B illustrating the prior art of Patent Document 12. FIG.

US Pat. No. 5,225,702 US Pat. No. 5,465,189 US Pat. No. 5,502,317 JP 09-107074 (page 3-7, FIG. 13) US Pat. No. 5,012,317 US Pat. No. 4,939,616 US Patent Application Publication No. 2002/0153571 US Patent Application Publication No. 2003/0075726 US Patent Application Publication No. 2002/0083250 JP 2003-203985 A US Patent Application Publication No. 2003/0164508 US Patent Application Publication No. 2003/0213971 Chatterjee A., Polgreen T., “A low-voltage triggering SCR for on-chip ESD protection at output and input pads”, IEEE Electron Device Letters, January 1991, Vol. 12, No. 1, p. 21-22 Ameraskera et al., “Substrate Triggering and Salicide Effects on ESD Performance and Protection Circuit Design in Submicron CMOS Processes”, IEDM, 1995, p. 547-550 Markus P. J. Mergens et al., “High Holding Current SCRs (HHI-SCR) for ESD Protection and Latch-up Immune IC Operation”, Electrical Overstress / Electrostatic Discharge Symposium Proceedings 2002 (1A.3.1) J. Wu et al., “Breakdown and latent damage of ultra-thin gate oxides under ESD stress conditions”, Electrical Overstress / Electrostatic Discharge Symposium Proceedings, 2002, p. 287-295

  However, with the miniaturization of CMOS LSI, the gate oxide film is becoming thinner, and the internal circuit is extremely vulnerable to excessive voltage application. As pointed out in Non-Patent Document 4, in the low voltage trigger SCR described in Patent Documents 1 to 3, the transition time until the resistance becomes low is long and the voltage overshoots during that time. There is a danger that an excessive voltage is applied to the gate electrode to cause breakdown of the gate oxide film. It is known that the transition time becomes longer as the anode-cathode interval becomes wider. However, in the low voltage trigger SCR, the interval cannot be reduced. This phenomenon is not limited to the low voltage trigger SCR, but is the same in the above-described conventional SCR.

In a product using a conventional low-resistance substrate, in an SCR in which the holding current needs to be set high, the holding voltage is set high by widening the anode-cathode interval and set to a desired value. In this method, the trigger current must be increased. In such an SCR structure, since the trigger circuit mainly discharges a surge current, the trigger voltage is determined by the sum of the trigger circuit and the resistance value of the current path in the SCR structure. Usually, in the SCR having a very low holding voltage, the trigger voltage is not so high because the trigger current is also as low as about 10 mA. There was no need to pay attention to these resistance values. However, the trigger current value is generally about 0.1 to 1 A, and these resistance values may not be ignored. The resistance value of the current path inside the SCR structure is not easy to calculate and tends to be high. If the resistance value is high, there is a risk that the trigger voltage will be high. For example, the resistance value in the N well is low in the low voltage trigger SCR shown in FIG. 27, and the P ⁺ / N well diode (between P ⁺ region 4 and N ⁺ region 5) is in the SCR described in Patent Document 10 shown in FIG. In the SCR described in Patent Document 4 shown in FIG. 30, the resistance value from the trigger P ⁺ layer 10 to the reference potential guard ring P ⁺ layer 10 causes the trigger voltage to increase. In the SCR described in Patent Documents 1 to 3, the trigger element forms part of the SCR structure. For this reason, the resistance value of the trigger element cannot be freely changed, and there is a problem in that there is a great limitation in adjusting the trigger voltage.

  On the other hand, in the SCR of products using a high-resistance substrate, such holding voltage adjustment is difficult, and in fact, for example, a method of increasing the overall holding voltage value by connecting diodes in series is adopted. Has been. Therefore, since attempts to use a high holding voltage have not been made widely, the triggering method of the SCR described in Patent Documents 4, 8 and 10 generally has a very low trigger current and is affected by its parasitic resistance. It can be ignored and these problems have not become apparent.

  In the HHI-SCR described in Patent Document 7 and Non-Patent Document 3, the holding voltage is adjusted while suppressing an increase in the trigger current, so that the current is shunted to the external resistor so that these resistors do not affect. The circuit is adopted. Non-Patent Document 3 describes that the product of the external resistance and current is about 0.7 V, and that the SCR is triggered when the diode is forward biased. However, for that purpose, since the other bipolar element constituting the SCR needs to be turned on, the trigger current needs to have a larger value. Considering this point, when such a structure is adopted, the trigger voltage is likely to be high when the external resistance value is set to a high value. Therefore, as described above, the SCR described in Patent Document 7 and Non-Patent Document 3 has a value in a range where the external resistance is low.

  The response speed of the diode is known to be extremely slow when a voltage is applied from the outside to supply a current, but in that case, the response time of the SCR may become long. One of the causes is that the resistance of the diode is high and current is not directly supplied to the diode itself. Another cause is that one bipolar element is operating and the other bipolar element is not operating. In Patent Document 7, this problem is solved by devising a circuit configuration. However, as in the holding voltage adjustment type SCR described in Patent Document 7 shown in FIG. 37, the method of performing double triggering with different trigger elements is as follows. There are cases where the timing for starting the current flow is not aligned. Therefore, for example, when a current flows to the N-well side, the hole current emitted from the PN diode flows into the P-well potential control electrode, but its resistance value is generally set low, so that the trigger current becomes high. There is a problem.

  Considering from the viewpoint of trigger operation, as pointed out in Patent Document 7 and Non-Patent Document 3, in order to efficiently trigger the SCR, it is close to a region where the anode and the cathode face each other. It is more efficient to forward bias the PN diode. However, as shown in FIG. 28, in the PN diode to which the trigger element described in Patent Document 10 is connected, current flows at a position opposite to the anode-cathode that is the current path of the SCR. There is a problem that the trigger is not efficient and the operation speed is lowered. Note that the method of supplying the trigger current to the N-well described in Patent Document 10 and the like is not preferable from the viewpoint of holding voltage control because the N-well resistance cannot be lowered. In the double trigger method of Patent Document 8, since the anode-cathode distance is too large, not only the dynamic resistance is increased, but also when the trigger tap is provided between the cathode and the N-well, the operation speed of the SCR is increased. It may be significantly reduced.

  As described above, there is a need for a structure that allows the vertical bipolar transistor elements 12 constituting the SCR to be conducted at high speed, a low trigger voltage, and a low layout area. In the past, there has been no electrostatic discharge protection element that can meet the above requirements, and there is a strong demand for the development of this type of electrostatic discharge protection element.

Further, as described in the background art described above, it is important to stably adjust the holding voltage of the SCR. In particular, in recent years, the STI process (Shallow Trench Isolation) has been used, and the resistance in the well often varies greatly. In practice, the N well resistance and the substrate resistance often depend on the area or layout of the N ⁺ region in the N well and the P ⁺ region in the P well, and the current amplification factor of each bipolar element constituting the SCR is also determined. There is a possibility that it is shifted due to a process change or the like, and there is a problem that when the SCR is applied to a product, it is necessary to combine performance such as holding voltage by trial manufacture and evaluation. Furthermore, in the SCR described in Patent Document 7, it is necessary to lower the N-well resistance and the P-well resistance to such an extent that it can be adjusted by an external resistance. In practice, however, the SCRs shown in FIGS. 27, 28A and 28B are used. As shown, since the electrodes are arranged on the lateral side, the substantial resistivity is hardly lowered and a resistance distribution is generated in the lateral direction. For this reason, the holding current of the SCR is determined at the substantially central portion of the anode and cathode electrodes that have the maximum resistance. Therefore, when the holding current must be set very high, the resistance does not decrease to a predetermined value, so the number of divisions must be increased. If the number of divisions is small, the holding current cannot be controlled, and the number of divisions is reduced. If the number is increased in advance, there is a problem that the layout area becomes extremely large.

  Furthermore, when the holding voltage of the SCR is adjusted by separating the cathode-N well edge interval described above, not only does the operation speed decrease, but the holding voltage, etc. If there is a deviation from the above parameters, new reticles must be prepared, and wafers that have been manufactured at the factory must be discarded. There is a problem of giving.

Furthermore, in the electrostatic discharge protection element described in Patent Document 6, a P ⁺ region is inserted between two N ⁺ regions in the N well, and a resistance element is added between the N ⁺ regions. In this structure, in order to turn on the SCR element, a voltage of a breakdown voltage of 40 V or more of the N well is applied to the protected element. Therefore, the current fine device cannot be applied because the withstand voltage is far below this value.

Furthermore, Patent Document 11 is a modified example of the low voltage trigger SCR, and as described above, there is a problem in the method of adjusting the operation speed and the trigger voltage. Furthermore, in Patent Document 12, it is described in the specification that such a structure is adopted in order to increase the current amplification factor of each bipolar transistor. As a result, the base resistance of each of the bipolar transistors constituting the SCR significantly decreases, and the SCR may not operate. 2A and 2B, which are prior arts of Patent Document 12, describe an SCR that does not form an STI structure between an anode and an N-well potential fixed electrode and between a cathode and a P-well potential fixed electrode. However, a high concentration PN junction such as this SCR has a problem that the leakage current becomes remarkably high, the current amplification factor decreases, and the SCR performance varies. Further, in the current CMOS product manufacturing process, all Si layers such as N ⁺ layer and P ⁺ layer that are not covered with the gate electrode are covered with the silicide electrode, but in the SCR described in Patent Document 12, between the anode and the cathode, However, since the silicide electrode is formed, the leakage current increases in this region and the SCR characteristic cannot be controlled.

The present invention has been made in view of such problems, and can operate a vertical bipolar transistor device at high speed, further reduce the layout area, and maintain the holding voltage, trigger voltage, and other elements. It is an object of the present invention to provide an electrostatic discharge protection element and an electrostatic discharge protection circuit whose performance can be easily adjusted.

  The present invention has the following features. However, the 1st conductivity type as described in a claim is described as P type, and the 2nd conductivity type is described as N type. However, the present invention is not limited to this, and a reverse conductivity type may be used.

  The electrostatic discharge protection element according to the first invention of the present application is:
  A P-type substrate or a P-type layer;
  An N well and a first P well formed adjacent to each other on the surface of the P type substrate or P type layer;
  A second P well formed on the surface of the P type substrate or the P type layer;
  A first high concentration N-type region, a second high concentration N-type region, and a first high concentration P-type region formed on the surface of the N well;
  A third high-concentration N-type region formed on the surface of the first P-well;
  A second high-concentration P-type region formed on the surface of the second P-well;
  Have
  The first high concentration N-type region and the first high concentration P-type region are connected to a first power source,
  The third high-concentration N-type region and the second high-concentration P-type region are connected to a second power source having a potential different from that of the first power source,
  The second high concentration N-type region is connected to a trigger current supply circuit,
  The trigger current supply circuit includes a MOS transistor connected between the second high-concentration N-type region and the second power supply,
  The first bipolar element constituted by the first high-concentration P-type region, the N-well and the P-type substrate or the P-type layer, the N-well, the P-type substrate or the P-type layer, and the third high It functions as a thyristor in cooperation with the second bipolar element constituted by the concentration N-type region,
  The first high-concentration P-type region and the third high-concentration N-type region are adjacent to each other.
  In the electrostatic discharge protection element, for example, by passing a current through the first high concentration N-type region and the first high concentration P-type region, the P-type substrate or P-type layer, the N well, and the first A current flows through the bipolar element constituted by the high concentration P-type region. In the electrostatic discharge protection element, the trigger current supply circuit may include a series diode connected between the second high-concentration N-type region and the second power supply instead of the MOS transistor. Good.

  The electrostatic discharge protection element according to the second invention of the present application is:
  A P-type substrate or a P-type layer;
  An N well and a first P well formed adjacent to each other on the surface of the P type substrate or P type layer;
  A second P-well formed on the surface of the P-type substrate or P-type layer;
  A first high concentration N-type region, a second high concentration N-type region, and a first high concentration P-type region formed on the surface of the N well;
  A third high-concentration N-type region formed on the surface of the first P-well;
  A second high-concentration P-type region formed on the surface of the second P-well;
  Have
  The first high concentration N-type region and the first high concentration P-type region are connected to a first power source,
  The third high-concentration N-type region and the second high-concentration P-type region are connected to a second power source having a potential different from that of the first power source,
  The second high concentration N-type region is connected to a trigger current supply circuit,
  The trigger current supply circuit includes a MOS transistor connected between the second high-concentration N-type region and the second power supply,
  The first bipolar element constituted by the first high-concentration P-type region, the N-well and the P-type substrate or the P-type layer, the N-well, the P-type substrate or the P-type layer, and the third high It functions as a thyristor in cooperation with the second bipolar element constituted by the concentration N-type region,
  The second high concentration N-type region and the third high concentration N-type region are adjacent to each other. In the electrostatic discharge protection element, the trigger current supply circuit may include a series diode connected between the second high-concentration N-type region and the second power supply instead of the MOS transistor. Good.

  The electrostatic discharge protection element according to the first or second invention of the present application may further have the following structural features, for example.
(A) Each of the first high-concentration N-type region and the second high-concentration N-type region includes a plurality of divided regions,
  The divided regions of the first high-concentration N-type region and the second high-concentration N-type region are alternately arranged in a direction orthogonal to the opposing direction of the second high-concentration P-type region and the third high-concentration N-type region. Are located in
  The first high-concentration P-type region extends between the divided regions.
(B) The first high-concentration N-type region is divided into two parts and arranged apart in a direction perpendicular to the opposing direction of the second high-concentration P-type region and the third high-concentration N-type region,
  The second high-concentration N-type region is disposed between the divided regions of the first high-concentration N-type region,
  The first high-concentration P-type region extends between the divided region of the first high-concentration N-type region and the second high-concentration N-type region.
(C) The third high-concentration N-type region is divided into two and arranged apart in a direction orthogonal to the facing direction of the second high-concentration P-type region and the third high-concentration N-type region,
  The N-well extends between the divided regions of the third high-concentration N-type region;
  The second high-concentration N-type region is disposed in the extension region of the N well.
(D) The first high-concentration N-type region and the third high-concentration N-type region are each divided into two and orthogonal to the facing direction of the second high-concentration P-type region and the third high-concentration N-type region. Are spaced apart in the direction,
  The N-well extends between the divided regions of the third high-concentration N-type region;
  The second high-concentration N-type region is disposed in an extension region of the N well, and the first high-concentration P-type region extends between the divided regions of the first high-concentration N-type region.
(E) The first high-concentration N-type region is divided into two parts and arranged apart in a direction perpendicular to the opposing direction of the second high-concentration P-type region and the third high-concentration N-type region,
  The first high-concentration P-type region has a portion near the third high-concentration N-type region at the center in the dividing direction of the first high-concentration N-type region.
  The second high-concentration N-type region is disposed in this notch.

  The electrostatic discharge protection element according to the third invention of the present application is:
  An N well and a P well formed on the surface of a P type substrate or P type layer;
  A first high concentration N-type region, a second high concentration N-type region, and a first high concentration P-type region formed on the surface of the N well;
  A third high concentration N-type region and a third high concentration P-type region formed on the surface of the P well;
  Have
  The first high concentration N-type region and the first high concentration P-type region are connected to a first power source,
  The third high-concentration N-type region is connected to a second power source having a potential different from that of the first power source,
  The second high concentration N-type region and the third high concentration P-type region are connected via a series diode,
  The first bipolar element constituted by the first high-concentration P-type region, the N-well and the P-type substrate or the P-type layer, the N-well, the P-type substrate or the P-type layer, and the third high It functions as a thyristor in cooperation with the second bipolar element constituted by the concentration N-type region,
  The second high concentration N-type region and the third high concentration N-type region are adjacent to each other.

  The electrostatic discharge protection element according to the fourth invention of the present application is:
  A P-type substrate or a P-type layer;
  An N well and a first P well formed adjacent to each other on the surface of the P type substrate or P type layer;
  A second P-well formed on the surface of the P-type substrate or P-type layer;
  A first high concentration N-type region, a second high concentration N-type region, and a first high concentration P-type region formed on the surface of the N well;
  A third high concentration N-type region and a third high concentration P-type region formed on the surface of the first P well;
  A second high-concentration P-type region formed on the surface of the second P-well;
  Have
  The first high concentration N-type region and the first high concentration P-type region are connected to a first power source,
  The third high-concentration N-type region and the second high-concentration P-type region are connected to a second power source having a potential different from that of the first power source,
  The second high concentration N-type region and the third high concentration P-type region are connected via a series diode,
  The first bipolar element constituted by the first high-concentration P-type region, the N-well and the P-type substrate or the P-type layer, the N-well, the P-type substrate or the P-type layer, and the third high It functions as a thyristor in cooperation with the second bipolar element constituted by the concentration N-type region,
  The second high concentration N-type region and the third high concentration N-type region are adjacent to each other.

  In the electrostatic discharge protection element according to the fourth invention of the present application,
  The third high-concentration N-type region is divided into two and arranged apart in a direction orthogonal to the opposing direction of the second high-concentration P-type region and the third high-concentration N-type region,
  The N-well extends between the divided regions of the third high-concentration N-type region;
  The second high-concentration N-type region is disposed in an extension region of the N well, and the third high-concentration P-type region is divided into two parts, so that the first high-concentration P-type region and the third high-concentration region are divided. You may arrange | position outside the opposing area | region with N type area | region.
  Furthermore, the N well may extend to the back of a region opposite to the divided region of the third high concentration P-type region and the second high concentration N type region.
  The width of the second high-concentration N-type region is preferably a minimum width that can form a contact within a range allowed by the design rule.

  The electrostatic discharge protection element according to the fifth invention of the present application is:
  A P-type substrate or a P-type layer;
An N-well formed on the surface of the P-type substrate or P-type layer;
  A first high concentration N-type region, a second high concentration N-type region, and a first high concentration P-type region formed on the surface of the N well;
  A third high-concentration N-type region, a second high-concentration P-type region, and a third high-concentration P-type region formed on the surface of the P-type substrate or P-type layer;
  A first resistance element connected between the first high-concentration P-type region and the second high-concentration N-type region;
  A second resistance element connected between the second high-concentration P-type region and the third high-concentration P-type region;
  Have
  The first high concentration N-type region and the first high concentration P-type region are connected to a first power source,
  The third high-concentration N-type region and the second high-concentration P-type region are connected to a second power source having a potential different from that of the first power source,
  The second high concentration N-type region is connected to a trigger current supply circuit,
  The first bipolar element constituted by the first high-concentration P-type region, the N-well and the P-type substrate or the P-type layer, the N-well, the P-type substrate or the P-type layer, and the third high It functions as a thyristor in cooperation with the second bipolar element constituted by the concentration N-type region,
  The second high concentration N-type region and the third high concentration N-type region are adjacent to each other.
  Here, it is preferable that the width of the second high-concentration N-type region is a minimum width capable of forming a contact within a range allowed by a design rule.

  The electrostatic discharge protection element according to the sixth invention of this application is:
  A P-type substrate or a P-type layer;
  An N well and a P well formed adjacent to each other on the surface of the P type substrate or P type layer;
  A first high-concentration N-type region, a first high-concentration P-type region, and a second high-concentration P-type region formed on the surface of the N well;
  A second high concentration N-type region and a third high concentration P-type region formed on the surface of the P well;
  Have
  The first high concentration N-type region and the first high concentration P-type region are connected to a first power source,
  The second high-concentration N-type region and the third high-concentration P-type region are connected to a second power source having a potential different from that of the first power source,
  The second high concentration P-type region is connected to a trigger current supply circuit;
  A first bipolar element constituted by the first high-concentration P-type region, the N-well and the P-type substrate or the P-type layer, the N-well, the P-type substrate or the P-type layer, and the second high It functions as a thyristor in cooperation with the second bipolar element constituted by the concentration N-type region,
  The second high concentration P-type region and the second high concentration N-type region are adjacent to each other.
  Here, the first high-concentration N-type region and the first high-concentration P-type region are each divided into a plurality of directions so that the first high-concentration N-type region and the first high-concentration P-type region face each other. Are arranged away from each other in a direction perpendicular to
  The second high-concentration P-type region may extend between the divided regions.
  The second high-concentration P-type region has a minimum width at which a portion extending between the divided regions can form a contact within a range allowed by a design rule,
  It is preferable that a portion other than the portion extending between the divided regions is less than the minimum width.

  The electrostatic discharge protection element according to the seventh invention of the present application is:
  A P-type substrate or a P-type layer;
  An N well and a P well formed adjacent to each other on the surface of the P type substrate or P type layer;
  A first high concentration P-type region and a first high concentration N-type region formed on the surface of the N well;
  A second high-concentration N-type region and a second high-concentration P-type region formed on the surface of the P-well;
  The first high-concentration P-type region is connected to a first power source;
  The second high-concentration N-type region and the second high-concentration P-type region are connected to a second power source having a potential different from that of the first power source,
  The first high concentration N-type region is connected to a trigger current supply circuit;
  The first bipolar element constituted by the first high-concentration P-type region, the N-well and the P-type substrate or the P-type layer, and the N-well, the P-well and the first high-concentration N-type region. Function as a thyristor in cooperation with the second bipolar element
  The first high concentration N-type region and the second high concentration N-type region are adjacent to each other,
  The first high-concentration P-type regions are each divided into a plurality of pieces and arranged apart in a direction perpendicular to the opposing direction of the second high-concentration N-type region and the second high-concentration P-type region,
  The first high-concentration N-type region extends between the divided regions.
  Here, it is preferable that the first high-concentration N-type region has a minimum width capable of forming a contact within a range allowed by a design rule.
  Further, it is particularly preferable that a portion of the first high concentration N-type region other than a portion extending between the divided regions is less than the minimum width.

  In the electrostatic discharge protection element according to the first to seventh inventions of the present application, a region where no silicide is formed or a gate electrode may be provided between adjacent high concentration regions.

  The electrostatic discharge protection element according to the eighth invention of the present application is:
  A P-type substrate or a P-type layer;
  An N well and a P well formed adjacent to each other on the surface of the P type substrate or P type layer;
  A first high concentration N-type region and a first high concentration P-type region formed on the surface of the N well;
  A second high concentration P-type region and a second high concentration N-type region formed on the surface of the P well;
  Have
  The N well and the P well are connected to a trigger current supply circuit,
  A first bipolar element comprising the P-type substrate or the P-type layer, the N well and the first high-concentration P-type region; the first high-concentration N-type region; the first high-concentration P-type region; In cooperation with the second bipolar element constituted by the second high-concentration N-type region, functions as a thyristor;
  The second high concentration P-type region and the second high concentration N-type region are adjacent to each other,
  A current flows through each well of each of the bipolar elements simultaneously.

  The electrostatic discharge protection element according to the ninth invention of the present application is:
  A P-type substrate or a P-type layer;
  An N well and a P well formed on the surface of the P type substrate or P type layer;
  A P-type first electrode formed on the surface of the N-well;
  A first high-concentration N-type region formed on the surface of the N-well and applied with the same potential as the first electrode;
  A second high concentration N-type region formed on the surface of the N well and connected to the trigger element;
  An N-type second electrode formed on the surface of the P-well;
  A first high-concentration P-type region formed on the surface of the P-well and applied with the same potential as the first electrode,
  The first high-concentration P-type region is disposed at a position away from a region where the first electrode and the second electrode are opposed to each other,
  A first bipolar element constituted by the P-type substrate or P-type layer, the N-well and the first electrode; and an N-well, the P-type substrate or P-type layer and the second electrode. In cooperation with the second bipolar element that functions as a thyristor,
  A trigger current flows in the N well.
  Here, a second high concentration P-type region may be provided on the surface of the P well, and the second high concentration P-type region may be connected to a trigger element.

The electrostatic discharge protection circuit according to the tenth invention of the present application is:
A first bipolar element and a second bipolar element that cooperate to function as a thyristor;
A trigger device for the first bipolar element and the second bipolar devices operated simultaneously,
A first resistance element;
A second resistance element;
One end of the trigger element is connected to the base region of the first bipolar element via the first resistance element,
The other end of the trigger element is connected to the base region of the second bipolar element via the second resistance element, and is grounded via the second resistance element. .

The electrostatic discharge protection circuit according to the eleventh aspect of the present invention is:
A P-type first well comprising a P-type first region and an N-type second region;
An N-type second well comprising a P-type third region and an N-type fourth region;
A trigger element;
Resistance,
With
The first bipolar element constituted by the first well, the second region and the second well and the second bipolar element constituted by the first well, the second well and the third region are cooperative. Working as a thyristor,
The other end of the trigger element is connected to the fourth region ;
One end of the resistor is connected to the first region,
The other end of the resistor is connected to the second region;
The trigger element is Ru actuates said first bipolar element and the second bipolar elements simultaneously, characterized in that.

The electrostatic discharge protection circuit according to the eleventh aspect of the present invention is:
Further comprising a pad,
The pad being connected to said first region through said resistor,
The one end of the trigger element may be connected to the second region through the resistor.
The electrostatic discharge protection circuit according to the eleventh aspect of the present invention is
Further comprising a second resistor,
Wherein the trigger element and the other end is connected to said third region via said second resistor, and may be grounded through the second resistor.

In the electrostatic discharge protection circuit according to the present eleventh invention, before Symbol first region and the second region is preferably configured so as not to interfere with each other by an insulating region formed therebetween. Similarly, it is preferable that the third region and the fourth region are also configured so as not to interfere with each other by the insulating region formed therebetween.

The electrostatic discharge protection circuit according to the twelfth invention of the present application is:
A first bipolar element and a second bipolar element that cooperate to function as a thyristor;
A trigger device for the first bipolar element and the second bipolar devices operated simultaneously,
Includes a resistance element, a,
Emitter region of said first bipolar element is connected via a front Ki抵 anti element to the base region of said first bipolar element,
One end of the trigger element is connected to a base region of the first bipolar element;
The other end of the trigger element is connected to a base region of the second bipolar element.

The electrostatic discharge protection circuit according to the thirteenth invention of this application is:
A first bipolar element and a second bipolar element that cooperate to function as a thyristor;
A trigger device for the first bipolar element and the second bipolar devices operated simultaneously,
Includes a resistance element, a,
One end of the trigger element is connected to a base region of the first bipolar element;
The other end of the trigger element is connected to a base region of the second bipolar element;
Base region of said second bipolar device is grounded via the front Ki抵 anti element, characterized in that.

The electrostatic discharge protection circuit according to the fourteenth aspect of the present invention is:
A first bipolar element and a second bipolar element that cooperate to function as a thyristor;
A trigger device for the first bipolar element and the second bipolar devices operated simultaneously,
Includes a resistance element, a,
One end of the trigger element is connected to a base region of the first bipolar element;
The other end of the trigger element is connected to the base region of the second bipolar element through the front Ki抵 anti element, characterized in that.

  According to the present invention, in the bipolar transistor constituting the SCR, the vertical PNP bipolar element is made conductive by passing a current through the N well, and the horizontal NPN bipolar element is made conductive by using the vertical PNP bipolar element as a trigger. Therefore, the SCR can be turned on at a high speed, and also in the holding voltage adjustment type SCR, it is possible to prevent an excessive voltage rise when a trigger current is passed through the N well. Further, since the vertical PNP bipolar element and the horizontal PNP bipolar element are simultaneously conducted, the SCR can be turned on at high speed.

Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a diagram showing a layout of each region of the electrostatic discharge protection element according to the first embodiment of the present invention, and FIG. 2 is a diagram showing a trigger system, showing an arrangement of each layer and a trigger current supply circuit. FIG. 3 is a diagram showing a modification of the trigger current supply circuit. The electrostatic discharge protection element of the present embodiment has a second P well 20a (see FIGS. 2 and 3) on the surface of the P ⁺ semiconductor substrate 1 (see FIGS. 2 and 3), similarly to the conventional example 1 shown in FIG. An element isolation insulating film, a first N well 21 and a first P well 20b (see FIGS. 2 and 3) are formed, and the first N well 21 and the first P well 20b are adjacent to each other. Yes.

In the second P well 20a, a P ⁺ layer 22 for preventing latch-up that becomes a ground potential is formed. In the first N well 21, an N ⁺ layer 23 of an N well potential fixing electrode and An N ⁺ layer 24 for supplying a trigger current and a P ⁺ layer 25 serving as an anode of the SCR are formed. In the electrostatic discharge protection element of this embodiment, the high concentration N ⁺ layer is an N ⁺ layer and the high concentration P ⁺ layer is a P ⁺ layer, and the N ⁺ layer and the P ⁺ layer are subjected to ion implantation processing. Later, heat treatment may be performed or heat treatment may not be performed, and the same applies to the following embodiments. Further, in the first P well 20b adjacent to the first N well 21, an N ⁺ layer 27 serving as a cathode of the SCR and a source 28 and a drain 29 of an NMOS transistor are formed. A gate electrode 30 is formed on the first P well 20b between the source 28 and the drain 29 via a gate insulating film. These P ⁺ layer 22, N ⁺ layer 23, N ⁺ layer 24, P ⁺ layer 25, and N ⁺ layer 27 are separated by an element isolation insulating film.

Also in this embodiment, the P ⁺ layer 25, the first N well 21, and the P ⁺ semiconductor substrate 1 constitute a vertical PNP bipolar transistor, and the N ⁺ layer 27, the first P well, and the like. 20b and the first N well 21 constitute a lateral NPN bipolar transistor.

  The present invention is characterized in that a path for generating a current is formed in the N well 21 in order to make the vertical PNP bipolar transistor constituting the SCR conductive.

In the present embodiment, in the case of power supply protection, the N well potential fixing electrode (N ⁺ layer 23) and the anode (P ⁺ layer 25) are common within the N well 21 or external electrodes. It is connected to a potential (Vdd in the case of power supply protection). The cathode (N ⁺ layer 27) and the latch-up preventing P ⁺ layer 22 are connected to the ground line Vss.

An N ⁺ layer 24 for supplying a trigger current is provided in the N well 21. A trigger current supply circuit such as an NMOS field effect transistor 40 (FIG. 2) or a diode 41 (FIG. 3) connected in series is inserted between the N ⁺ layer 24 and the ground electrode.

In the trigger current supply circuit shown in FIG. 2, a transistor 33 and a resistor 32 are connected in series between a power supply Vdd and a ground line Vss, and an NMOS is connected to a connection point between the transistor 33 and the resistor 32. The gate of the transistor 40 is connected. The drain of the NMOS transistor 40 is connected to the trigger current supply N ⁺ layer 24, and the source is connected to the ground line Vss.

In the trigger current supply circuit shown in FIG. 3, a plurality of diodes 41 connected in series are connected between the trigger current supply N ⁺ layer 24 and the ground line Vss. When a voltage is applied to these trigger current supply circuits, the resistance value of the circuit becomes low and becomes a current path.

Next, the operation of the electrostatic discharge protection element of the present embodiment configured as described above will be described. When a surge current flows, first, a voltage is applied to the trigger current supply circuit, the resistance value of the circuit is lowered, and a current path is formed. That is, the current flows from the N well potential fixing electrode (N ⁺ layer 23) connected to the power source Vdd to the ground line via the trigger current supply N ⁺ layer 24. In the process, a potential difference is generated in the N well 21 by the product IR of the N well resistance and the current. Accordingly, the potential in the vicinity of the bottom surface of the P ⁺ layer 25 (anode) becomes lower than the reference potential (power supply potential) according to the amount of flowing current, and P ⁺ N formed by the P ⁺ layer 25 and the N well 21. The diode becomes forward biased. Therefore, the vertical PNP parasitic bipolar transistor in this region starts to turn on, and current is distributed toward the substrate.

FIG. 4 is a sectional view of an example in which the electrostatic discharge protection element shown in FIG. 1 is applied to an input protection element. At this time, as shown in FIG. 4, the trigger current flows from the N ⁺ layer 23 to the trigger current supply terminal (path C) via the N well (path A) and the N ⁺ layer 24 (path B). Furthermore, it flows to the trigger current supply circuit. Further, the N well potential in the vicinity of the PN junction region on the bottom surface of the anode is lower than the potential difference generated in the current path A and path B, that is, the pad potential. As can be seen from the current distribution in comparison with FIG. 25, the potential of the entire anode bottom changes. Therefore, the SCR turn-on operation can be performed more efficiently. In the fine CMOS process, since the minimum value of the element separation interval is as extremely narrow as 0.1 to 0.2 μm, the resistance value in the path B is relatively low. Further, in the path A and the path C, there are cases where the resistance of the connection portion of the high concentration N ⁺ diffusion and the N well is high, such as a retrograded well structure separated by STI. Considering these, the potential difference component in the path A is dominant, and it is advantageous that the trigger current supply N ⁺ layer has a large area. On the other hand, from the viewpoint of increasing the holding voltage, it is desirable to decrease the N-well resistance, and various layouts are determined in consideration of actual resistance values from these viewpoints. From the viewpoint of increasing the holding voltage, an external resistor may be provided between the trigger current supply electrode and the N-well electrode in order to reduce the clamp voltage at the time of SCR trigger.

  Since the increase in the substrate potential means the increase in the base potential in the lateral NPN bipolar transistor, the lateral NPN bipolar transistor is also turned on.

  Then, the generated electron current is supplied again to the N-well 21 to promote conduction of the vertical bipolar, positive feedback is applied, and a high-speed, low-resistance current path is formed between the anode and the cathode. .

Normally, in the SCR, the turn-on speed is higher when the distance between the anode and the cathode is shorter. Therefore, as shown in FIG. 1, the formation position of the N ⁺ layer 24 for supplying the trigger current is the anode. The (P ⁺ layer 25) is provided on the opposite side of the cathode (N ⁺ layer 27), and the anode (P ⁺ layer 25) and the cathode (N ⁺ layer 27) are arranged close to each other.

  In the conventional example, the power supply protection (trigger current supply circuit) connected to Vdd is turned on and current flows, whereby the vertical PNP bipolar is turned on. Since this is a forward current of the PN diode, the operation speed is slow, it takes time until the resistance becomes low (turns on), and the inter-element voltage may increase. Further, as described in the background magic, the diode current path between the trigger electrode and the anode is opposite to the position between the anode and the cathode of the SCR, so that the trigger is not efficiently performed. On the other hand, as described above, since the current is directly supplied to the N well 21 according to the present invention, the potential at the bottom of the anode can be lowered over a wide range, and the SCR can be turned on at high speed.

Next, an electrostatic discharge protection element according to a second embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the trigger current supply N ⁺ layer 24 is disposed in the N well 21 in the vicinity of the N ⁺ layer 27 serving as the cathode of the SCR in the adjacent P well 20 b, and the SCR in the N well 21 is disposed. The P ⁺ layer 25 serving as the anode is disposed between the N ⁺ layer 23 of the N well potential fixing electrode and the trigger current supply N ⁺ layer 24. Therefore, the trigger current supply N ⁺ layer 24 is provided in the N well 21 between the anode and the cathode. Also in this case, the shortest distance is set between the N well 21 and the cathode. The N-well-anode interval is 1 to 2 μm. However, in the operation of the SCR, the speed until the base width of the lateral bipolar transistor is mainly turned on is determined. In many cases, the speed until turn-on is not greatly affected.

However, the arrangement of the P ⁺ layer 24 that is the P ⁺ guard ring in the electrostatic discharge protection element or the local ground of the SCR (ground provided beside the cathode of the SCR) differs depending on the manufacturing process. For example, the electrostatic discharge protection element of the first embodiment shown in FIG. 1 and the conventional example 2 shown in FIG. 30 is arranged on the assumption that a low resistance substrate is used. For this reason, the resistance of the silicon substrate serving as the bottom surface of the SCR is extremely small, and the potential of the SCR does not affect the arrangement of the P ⁺ guard ring and the local ground. 7A is a plan view showing the layout of the electrostatic discharge protection element of the first modification of the first embodiment shown in FIG. 1, and FIG. 7B is the layout of the electrostatic discharge protection element of the second modification. FIG. 8A is a plan view showing the layout of the electrostatic discharge protection element of the first modification of the second embodiment shown in FIG. 4, and FIG. 8B is the electrostatic discharge protection element of the second modification. FIG. In the electrostatic discharge protection element of the first modification shown in FIGS. 7A and 8A, a high resistance substrate is used, and the potential around the SCR is determined by the local ground. Moreover, the electrostatic discharge protection element of the 2nd modification shown in FIG.7 (b) and FIG.8 (b) arrange | positions the anode and the cathode as object. The positions of the trigger supply N ⁺ layer 24 and the N ⁺ layer 23 of the N well potential fixing electrode in the present modification may be reversed.

  According to a further test by the present inventors, the electrostatic discharge protection element of Conventional Example 2 shown in FIG. 30 has a result that the trigger current can be lowered by bringing the trigger location as close as possible to the vicinity of the cathode of the SCR. This is because the potential of the region through which the SCR current flows efficiently increases, but from the opposite viewpoint, the width of the cathode 9 needs to be extremely narrow. This is not practical because a predetermined number of contacts must be placed on the cathode. On the other hand, in the present invention, since the trigger electrode is provided in the N well, the region where the N well is formed is limited to a narrow range, so that the current density is increased and the potential drop is efficiently reduced. It can be carried out. This is because, as described above, the potential across the bottom surface of the PN junction of the anode is lowered by flowing a current over a wide range in the N well, and the vertical PNP bipolar element in the N well is the first to operate. When conducting, the hole current flows from there toward the lower potential, so that the base potential of the lateral NPN bipolar element can be increased efficiently even when the substrate resistance is low. Therefore, for example, in the case of the structure of the second modification shown in FIGS. 7B and 8B, the N well is the center, and the flow of hole current can be used more effectively. High effect. For the reasons described above, the arrangement of the trigger layer in the present invention is not limited to these, and can be arranged arbitrarily. In other embodiments, the arrangement of the trigger layer is the same as that described above. Similarly to the electrostatic discharge protection element of the embodiment and its modification, it can be designed and optimized by the process, and therefore can be applied to a holding voltage adjustment type electrostatic discharge element.

In the case of the first embodiment shown in FIGS. 1 to 4, the trigger current (current supplied from the N ⁺ layer 23 of the N well potential fixing electrode) does not pass through the P ⁺ layer 25 side, and the trigger current Since the current flows to the N ⁺ layer 24 for supply, the effect of lowering the potential of the bottom surface of the P ⁺ layer 25 is limited (compared to other embodiments), but the second shown in FIGS. In the embodiment, since a current flows below the P ⁺ layer 25, a potential difference between the bottom surface of the P ⁺ layer and Vdd can be effectively generated. For this reason, the SCR element can be turned on at higher speed. In this case, since the N ⁺ layer 24 is arranged in the path through which the surge current flows, thermal destruction may occur due to the influence of the temperature rise. However, this can be avoided by contrivance such as arrangement of metal wiring or contacts, and in fact, the protected element often breaks due to the high voltage before the protective element itself breaks down. This is an effective method from the viewpoint that it is advantageous to measure the high-speed operation.

Next, an electrostatic discharge protection element according to a third embodiment of the present invention will be described with reference to FIG. In the present embodiment, the N well 21 has an N well potential fixing electrode N in a direction perpendicular to the opposing direction of the P ⁺ layer 22 in the P well 20a and the N ⁺ layer 27 in the P well 20b. ^{The +} layers 23 and the trigger current supply N ⁺ layers 24 are alternately arranged. One comb-shaped P ⁺ layer 25 (anode) is arranged so as to enter between the N ⁺ layer 23 and the N ⁺ layer 24.

In the electrostatic discharge protection element of the present embodiment configured as described above, the distance between the anode (P ⁺ layer 25) and the cathode (N ⁺ layer 27) can be made the shortest distance, and the trigger current is P ⁺ layer. Since it passes under 25, it becomes easy to make a potential difference. Further, since the resistance value between the N ⁺ layer 23 of the N well potential fixing electrode and the trigger current supply N ⁺ layer 24 can be lowered, the trigger voltage of the SCR can be lowered. Further, by alternately arranging these layers, current can flow to the bottom surface of the P ⁺ layer 25, so that the SCR element can be turned on at high speed.

Next, an electrostatic discharge protection element according to a fourth embodiment of the present invention will be described with reference to FIG. This embodiment has a layout similar to that of the third embodiment shown in FIG. 9, except that a pair of N ⁺ layers 23a and 23b serving as N well potential fixing electrodes are connected to both end portions (P ⁺ The third embodiment is that the trigger current supply N ⁺ layer 24 is arranged at the center between the N ⁺ layers 23a and 23b, and is arranged at both ends in the direction orthogonal to the opposing direction of the layer 22 and the N ⁺ layer 27. And different.

In the fourth embodiment, when a current flows from the pair of N ⁺ layers 23a and 23b into the central portion of the N well 21, the potential difference between both ends of the central portion of the N well 21 increases. The SCR is triggered by the conduction of the PNP vertical bipolar.

Next, a fifth embodiment of the present invention will be described with reference to FIG. In the present embodiment, the N ⁺ layers 27a and 27b divided into two are formed as the cathode, and the N well 21 is extended between these N ⁺ layers 27a and 27b. Then, an N ⁺ layer 24 for supplying a trigger current is disposed on the extending portion of the N well 21. This embodiment has the same effects as the above embodiments, and the trigger current flows under the P ⁺ layer 25.

Next, a sixth embodiment of the present invention will be described with reference to FIG. In the present embodiment, the N-well potential fixing electrode is divided into two N ⁺ layers 23a and 23b, and the anode P ⁺ layer 25 is disposed in the N well 21 including the space between the N ⁺ layers 23a and 23b. However, this is different from the fifth embodiment shown in FIG. This embodiment also has the same effects as the above embodiments.

Next, a seventh embodiment of the present invention will be described with reference to FIG. In the electrostatic discharge protection element of this embodiment, a pair of N ⁺ layers 23a and 23b are applied to the N well potential at both ends in the direction orthogonal to the opposing direction of the P ⁺ layer 22 and the N ⁺ layer 27 in the N well 21. It is arranged as a fixing electrode, and between these N ⁺ layers 23a and 23b, an anode P ⁺ layer 25 is formed in a shape in which a portion near the cathode N ⁺ layer 27 at the center in the longitudinal direction is cut out. An N ⁺ layer 24 for supplying a trigger current is disposed in the notch.

In this embodiment, the trigger current flows in the direction indicated by the arrow, and the current resistance product (IR) biases the PN junctions on the lower surfaces of the N ⁺ layers 23a and 23b of the N well potential fixing electrode in the forward direction. Therefore, a region close to the N well 21 of the vertical bipolar transistor in the N well is turned on first, and current flows in the direction of the substrate. As described above, in order to turn on the operation of the SCR, it is efficient to increase the potential in a region near the base of the lateral bipolar transistor (between the SCR anode and cathode). This embodiment is preferable in this respect.

FIG. 14 is a diagram showing an electrostatic discharge protection element according to an eighth embodiment of the present invention, and FIG. 15 is a diagram showing a trigger system, showing the arrangement of each layer and a trigger current supply circuit. In the present embodiment, a P ⁺ layer 22 for preventing latch-up that becomes a ground potential is formed in the second P well 20a, and an N ⁺ layer 23 that becomes an N well potential fixing electrode is formed in the N well 21. The N ⁺ layer 24 for supplying a trigger current and the P ⁺ layer 25 serving as an anode are formed in this order from the P ⁺ layer 22 side, and on the anode (P ⁺ layer 25) side in the first P well 20b. The N ⁺ layer 27 serving as a cathode is formed, and the P ⁺ layer 26 for supplying a trigger current is further formed.

A series-connected diode 41 of the trigger current supply circuit is connected between the N ⁺ layer 24 in the N well 21 and the P ⁺ layer 26 in the first P well 20b. Further, the P ⁺ layer 22 of the ground contact and the N ⁺ layer 27 of the cathode are commonly connected to the ground line Vss, and the N ⁺ layer 23 of the N well potential fixing electrode and the P ⁺ layer 25 of the anode are Commonly connected to the power supply Vdd.

In the present embodiment, a trigger current supply circuit (series diode 41) is arranged so as to connect the N well 21 and the P well 20b so that a current flows between the two wells. When the substrate 1 is a low resistance substrate (a substrate having a very low substrate resistance, a thin epitaxial film grown thereon, and a substrate having a very low resistivity), a trigger current is immediately adjacent to the cathode (N ⁺ layer 27). When the supply P ⁺ layer 26 is disposed, the PN diode is forward-biased in addition to the path for supplying current directly to the substrate, the diode 41 is turned on, and the electron current is emitted, whereby the electron Current is absorbed by the N-well 21. That is, the circuit configuration is such that the vertical PNP and the horizontal NPN bipolar transistor are made to conduct substantially simultaneously, and the SCR is turned on at high speed.

FIG. 16 is a diagram showing an electrostatic discharge protection element according to the ninth embodiment of the present invention. 16 is different from FIG. 11 in that the P ⁺ layers 26a and 26b for supplying the trigger current are arranged on the lateral sides of the P ⁺ layer 25 (anode) and the N ⁺ layers 27a and 27b (cathode) constituting the SCR. You may arrange | position in (the position which remove | deviated from the area | region where an anode and a cathode oppose).

As a result, a current path flowing through the N well 21 is formed as indicated by an arrow in the figure. Further, the current flowing from the P ⁺ layers 26 a and 26 b to the N ⁺ layer 24 flows in the SCR.

FIG. 17 is a view showing an electrostatic discharge protection element according to the tenth embodiment of the present invention. This embodiment is different from the embodiment shown in FIG. 16 in that the portions 21 a and 21 b of the N well 21 are located behind the current path from the P ⁺ layers 26 a and 26 b for supplying the trigger current to the N ⁺ layer 24. Is.

Thus, ^{P +} layers 26a, substrate current toward the ^{N +} layer 24 from 26b, a portion 21a of the N-well 21, is blocked by 21b, the substrate current can easily flow toward the ^{N +} layer 24. Thus, when forming a current path through which the current from the N well 21 flows to the substrate, the current in the substrate direction spreads from the P ⁺ layers 26a and 26b into the SCR. The electrostatic discharge protection element of the present invention is not limited to the structure shown in FIGS. 13, 16 and 18, and for example, a plurality of these are arranged with the SCR shown in FIGS. It may be a thing.

Next, with reference to FIG. 18, the electrostatic discharge protection element concerning 11th Embodiment of this invention is demonstrated. The electrostatic discharge protection element of this embodiment is a holding voltage adjustment type SCR, and an N well 21 is formed on the surface of the P ⁺ semiconductor substrate 1, and the N ⁺ of the N well potential fixing electrode is formed on the surface of the N well 21. A layer 23, an anode P ⁺ layer 25, and an N ⁺ layer 24 for supplying a trigger current are formed. A cathode N ⁺ layer 27, a trigger current supply P ⁺ layer 26, and a latch-up preventing ground contact P ⁺ layer 22 are formed on the surface of the P ⁺ semiconductor substrate 1. A pad 51 is connected to the N ⁺ layer 23 of the N well potential fixing electrode and the P ⁺ layer 25 of the anode, and the trigger current supply circuit (in FIG. 2) is connected to the N ⁺ layer 24 for supplying the trigger current. The NMOS transistor 40 or the serial diode 41 in FIG. 3 is connected, and the N ⁺ layer 24 and the N ⁺ layer 23 and the P ⁺ layer 25 are connected to the resistance element 52. Further, the latch-up prevention P ⁺ layer 22 and the cathode N ⁺ layer 27 are connected to the ground, and the trigger current supply P ⁺ layer 26 is connected to the ground via the resistance element 53.

In the present embodiment configured as described above, the trigger current is supplied from the trigger circuit during the SCR operation, and the vertical bipolar is operated. Therefore, the trigger voltage is higher than that of the prior art described in Patent Document 6. , Can be significantly lower. In addition, as the resistance elements 52 and 53, a large number of resistance elements can be arranged in advance, and these resistance elements can be selected and connected using the upper layer wiring so that a desired resistance value can be obtained. Since the SCR characteristics can be finally adjusted, there is an advantage that the adjustment of the SCR characteristics can be easily performed when the process is changed. For example, the holding voltage can be adjusted by changing the resistance value of the resistance element 53 when the resistance value of the resistance element 52 is set to 10Ω or less in order to push the clamp voltage until the SCR is turned on low. While using the resistive elements 52 and 53 in FIG. 18, the addition to, the ^{P +} layer 22 as a ^{P +} guard ring connected area of ^{the P +} layer 26 as a ^{P +} tap, or to ground The resistance value may be adjusted by the distance of

Further, if the trigger current supply N ⁺ layer 24 also serving as the (N well) potential adjusting layer is disposed between the anode P ⁺ layer 25 and the N well 21, an external resistance can be used to increase the holding current. Must be lower than the N-well resistance. In the electrostatic discharge protection element of this embodiment, when the product of the trigger current and the external resistance value is about 0.7 V, the PN diode between the anode and the trigger electrode is turned on to supply the hole current. start. As shown in FIG. 18, in the electrostatic discharge protection element of this embodiment, since the cathode N ⁺ layer 27 and the position where the hole current is supplied are close to each other, the SCR can be brought into a latched state in a very short time. Furthermore, as is apparent from the electrostatic discharge protection element according to this embodiment compared to the layout of the electrostatic discharge protection element described in Patent Document 7 shown in FIG. 26, most of the periphery of the anode is for (N-well) potential adjustment. Since it is surrounded by the trigger current supply N ⁺ layer 24 which also serves as a layer, the resistance range of the external resistance element can be selected by an amount corresponding to the reduction of the N-well resistance, so that the controllability of the potential is very good. As described above, since the structure shown in FIG. 33 cannot be applied to an SCR with a high trigger current, the advantage of the SCR of this embodiment is clear.

For element isolation between layers, a LOCOS (Local Oxidation of Silicon) method or an STI method is usually applied as shown in FIG. 24. For example, as shown in FIG. And a method of providing a gate electrode as shown in FIG. 19B and implanting N ⁺ layer forming impurities and P ⁺ layer forming impurities on both sides of the gate electrode. is there. In these methods, a low-resistance conductive layer is often formed on the surface side, and the substrate resistance and N-well resistance (base resistance of each bipolar element) indicated by the SCR transmission circuit can be lowered.

Next, an electrostatic discharge protection element according to the twelfth embodiment of the present invention will be described. FIG. 20 is a plan view showing the layout of the electrostatic discharge protection element of this embodiment. The electrostatic discharge protection element of this embodiment is the same as that of the above-described eighth embodiment except for the N-well electrical control electrode 23 from the electrostatic discharge protection element of the eighth embodiment shown in FIG. is there. The P ⁺ layer 31 becomes a P-well potential control electrode by connecting to an external resistor, and becomes a P-well potential fixed electrode by directly connecting to the anode or the cathode through an external wiring. Such an arrangement makes it difficult to reduce the resistance value on the N-well side, so that the holding current cannot be set high, but the area is reduced as compared with the electrostatic protection element of the eighth embodiment described above. be able to.

Next, a thirteenth electrostatic protection element of the present invention will be described. FIG. 21A is a plan view showing the layout of the electrostatic discharge protection element of this embodiment, and FIG. 21B is a plan view showing the layout of the electrostatic protection element of the first modification. In the SCR in the electrostatic discharge element of the above-described embodiment, a contact 35 must be formed on the layer in order to connect the trigger current supply N ⁺ layer 24 and the trigger element. In the process investigated by the present inventors, the distance between the P ⁺ layer 25 serving as the anode and the edge of the N well 21 is required to be about 0.9 to 1.0 μm even when the distance is designed to be minimum. In the above-described embodiment, this value is applied. In the process studied by the present inventors, the distance between the anode and the N-well edge and the distance between the cathode and the N-well edge are 0.2 to 0.3 μm, and need to be increased by about 3 times. In general, the dynamic resistance of the SCR is the resistance of the current path between the anode and the cathode. Therefore, when the distance between the anode and the cathode is widened, the resistance increases and the breakdown current decreases. It is considered that characteristics other than the dynamic resistance basically depend on the cathode-N well distance rather than the anode-N well distance. However, since the characteristics of the SCR are affected by the concentration distribution of the N well or the P well, the shape of the element, and the like, it cannot be generally said whether the degree of deterioration is a problem value. Therefore, assuming the worst case, it is necessary to design the SCR so that the distance between the anode and the N-well edge is minimized.

However, for example, these points have not been studied in the conventional electrostatic discharge protection element described in Patent Document 7 and the like. Actually, in the SCR having such a structure, in order to maximize the performance, unless the distance between the anode and the N-well edge is designed to be a minimum value, the characteristics of the element greatly vary. Therefore, in the electrostatic protection element of this embodiment, as shown in FIG. 21A, an N ⁺ layer 32 for contact formation is formed on the lateral side of the anode so that the anode-N well edge distance 36 is minimized. And a potential is connected by the contact forming N ⁺ layer 32. Thereby, the anode-N well edge interval can be reduced to 0.7 μm. As a result, the breakdown current can be increased by about 20%, and the dynamic resistance can also be decreased. As shown in FIG. 21 (b), the holding current may be adjusted by forming a layer resistance in the N well 21 and changing the connection of the metal wiring.

  Next, an electrostatic discharge protection element according to a fourteenth embodiment of the present invention will be described. FIG. 22 is a plan view showing the layout of the electrostatic discharge protection element of this embodiment. As shown in FIG. 22, the electrostatic discharge protection element of the present embodiment is obtained by removing the N-well potential fixing electrode of the electrostatic discharge protection element of the thirteenth embodiment, and otherwise the electrostatic discharge protection element of the thirteenth embodiment. The effect is the same as that of the discharge protection element. Thereby, an area can be reduced.

  Next, an electrostatic discharge protection element according to a fifteenth embodiment of the present invention will be described. FIG. 23 is a plan view showing the layout of the electrostatic discharge protection element of the present embodiment. As shown in FIG. 23, the electrostatic discharge protection element of the present embodiment is an element in which the contact formation region of the N well potential fixing electrode of the electrostatic discharge protection element of the thirteenth embodiment is arranged between the divided cathodes. is there. In the present embodiment, a trigger electrode, which is a holding current control electrode, is also provided near the cathode, so that the electron currents emitted from the cathode can be compared efficiently. Thereby, the controllability of the holding current can be improved.

Next, an electrostatic discharge protection element according to the sixteenth embodiment of the invention will be described. FIG. 24 is a cross-sectional view showing the electrostatic discharge protection element of this embodiment. As shown in FIG. 24, in the electrostatic discharge protection element of this embodiment, an N ⁺ layer 24 for supplying a trigger current that also serves as an anode 25 and an N-well potential control electrode is formed in an N-well 21, and the P-well has A trigger current supply P ⁺ layer 31 that also serves as the cathode 27 and the P-well potential control electrode is formed. The trigger current supply layer 31 is connected to each reference potential via a resistance element. The trigger current is supplied from an intermediate point obtained by dividing the resistance element, and for example, an NMOS transistor is connected to both trigger current supply terminals. The resistance values R _1N and R _1P of each resistance element are both 2Ω, and the resistance values R _2N and R _2P are set so that the holding voltage becomes a desired value.

  Thereby, when a surge current flows in, first, the NMOS transistor in the trigger circuit snaps back, and a current flows through each resistance element. Usually, since the well resistance in the SCR cannot be set so low, most of the current passes through the resistance element. When the product of the resistance value and the current value reaches about 0.7 V, both PN diodes begin to be forward biased. In this embodiment, both the hole current from the anode 25 and the electron current from the cathode 27 are instantly latched up because there is no place to be absorbed in the SCR structure. In addition, the trigger current is also lower and higher in performance than the above-described embodiment and the conventional holding voltage adjustment type SCR. As described above, it is extremely advantageous that the operating parameters of the SCR can be easily set by the external resistance element because the ease of design can be improved.

  Since the actual layout requires that the N-well resistance and the P-well resistance can be lowered, the depth of the anode 25 and the cathode 27 is reduced so as to increase the latching speed. The layout described in can be applied. Further, in the present embodiment, an electrostatic discharge protection element having a double trigger SCR structure is shown. However, this electrostatic discharge protection element is also characterized by a method of connecting a trigger current, and the resistance value setting is possible even if the trigger is only on one side. This is an effective method because it improves ease.

  However, in a normal STI isolation device structure, the well resistance is unlikely to be low. Next, an electrostatic discharge protection element according to a seventeenth embodiment of the present invention will be described. FIG. 25 is a plan view showing the layout of the electrostatic discharge protection element of this embodiment. As shown in FIG. 25, the electrostatic discharge protection element of this embodiment assists triggering by arranging a number of PN diodes in the P well near the cathode and a number of PN diodes in the N well near the anode. It has a structure. Thereby, since the diode resistance value can be lowered, the adjustment of the external resistance becomes unnecessary or easy, and the trigger can be performed more quickly. This additional diode may be provided only in the P well.

Next, an electrostatic discharge protection element according to the eighteenth embodiment of the invention will be described. FIG. 26 is a cross-sectional view showing the electrostatic discharge protection element of this embodiment. As shown in FIG. 26, the electrostatic discharge protection element of the present embodiment includes a trigger current supply N ⁺ layer 24 that also functions as the anode 25 and the N well potential control electrode, and a trigger current supply P that also functions as the cathode 27 and the N well potential control electrode. ^{Between the +} layers 26, a structure having a lower resistance than that shown in FIG. 19 is applied. This resistance value can be made an order of magnitude lower than that of a normal STI isolation layer. Therefore, in order to increase the holding current of the SCR, it is necessary to set the external resistance to about 10 to 100Ω. However, since the resistance value of the diode inside the SCR structure is extremely low, most of the current flows through this diode during the trigger operation. Therefore, even if a current flows between the trigger current supply circuit and the trigger current supply 2 terminal, the clamp voltage can be increased lower than that in the sixteenth embodiment. Further, since the current is not shunted, the trigger current is large, the trigger operation can be generated at a higher speed, and the trigger current can be reduced.

In the electrostatic discharge protection element of this embodiment, the gap between the anode 25 and the trigger current supply N ⁺ layer 2 and between the cathode 27 and the trigger current supply P ⁺ layer 26 are the same as those shown in FIG. Although the structure shown in a) is used, the present invention is not limited to this, and for example, the structure shown in FIG. The most important point in this embodiment and the above-mentioned sixteenth embodiment is that the vertical PNP and the horizontal NPN bipolar elements are made to conduct at the same time, and a plurality of trigger circuits are provided, and current is supplied to them simultaneously. Also good. For example, when two trigger circuits are provided as in the SCR shown in FIG. 37, an additional circuit capable of starting a current flow at the same time is provided, or a part of the two trigger circuits is shared to be substantially the same. By allowing the circuit to be handled as a circuit, it is possible to simultaneously pass current through the two trigger circuits. Furthermore, the electrostatic discharge protection element of the present invention is not limited to the electrostatic discharge protection element of the first to eighteenth embodiments described above, and may be a combination of these structures. Furthermore, the electrostatic discharge protection element of the present invention can be applied to a process using an SOI substrate.

It is a figure which shows the layout of the electrostatic discharge protection element of 1st Embodiment of this invention. It is a figure which shows the arrangement | positioning of each layer in the electrostatic discharge protection element of 1st Embodiment of this invention, and the equivalent circuit of a trigger current supply circuit. It is a figure which shows the modification of the trigger current supply circuit in the electrostatic discharge protection element of 1st Embodiment of this invention. It is sectional drawing of the example which applied the electrostatic discharge protection element shown in FIG. 1 to the input protection element. It is a figure which shows the layout of the electrostatic discharge protection element which concerns on 2nd Embodiment of this invention. It is a figure which similarly shows the arrangement | positioning of the each layer, and the equivalent circuit of a trigger current supply circuit. (A) is a figure which shows the layout of the electrostatic discharge protection element of the 1st modification of 1st Embodiment of this invention, (b) is a figure which shows the layout of the electrostatic protection element of a 2nd modification. (A) is a figure which shows the layout of the electrostatic discharge protection element of the 1st modification of 2nd Embodiment of this invention, (b) is a figure which shows the layout of the electrostatic protection element of a 2nd modification. It is a figure which shows the layout of the electrostatic discharge protection element which concerns on 3rd Embodiment of this invention. It is a figure which shows the layout of the electrostatic discharge protection element which concerns on 4th Embodiment of this invention. It is a figure which shows the layout of the electrostatic discharge protection element which concerns on 5th Embodiment of this invention. It is a figure which shows the layout of the electrostatic discharge protection element which concerns on 6th Embodiment of this invention. It is a figure which shows the layout of the electrostatic discharge protection element which concerns on 7th Embodiment of this invention. It is a figure which shows the layout of the electrostatic discharge protection element which concerns on 8th Embodiment of this invention. It is a figure which similarly shows the arrangement | positioning and connection aspect of each layer. It is a figure which shows the layout of the electrostatic discharge protection element which concerns on 9th Embodiment of this invention. It is a figure which shows the layout of the electrostatic discharge protection element which concerns on 10th Embodiment of this invention. It is sectional drawing of the electrostatic discharge protection element which concerns on 11th Embodiment of this invention. (A) is sectional drawing which shows the method of providing the area | region where a silicide is not formed on a cathode layer, and isolate | separating an element, (b) is an impurity for N ^<+> layer formation, and P ^<+> layer formation for a gate electrode. It is sectional drawing which shows the method of isolate | separating an element by injecting each impurity. It is a top view which shows the layout of the electrostatic discharge protection element of 12th Embodiment of this invention. (A) is a top view which shows the layout of the electrostatic discharge protection element of 13th Embodiment of this invention, (b) is a top view which shows the layout of the electrostatic discharge protection element of the 1st modification. It is a top view which shows the layout of the electrostatic discharge protection element of 14th Embodiment of this invention. It is a top view which shows the layout of the electrostatic discharge protection element of 15th Embodiment of this invention. It is sectional drawing which shows the electrostatic discharge protection element of 16th Embodiment of this invention. It is a top view which shows the layout of the electrostatic discharge protection element of 17th Embodiment of this invention. It is sectional drawing which shows the electrostatic discharge protection element of 18th Embodiment of this invention. It is a top view which shows the layout of the electrostatic discharge protection element of the prior art example 1. It is sectional drawing by the AA line shown in FIG. It is the graph which took the voltage on the horizontal axis and took the current on the vertical axis, and compared the characteristics of various SCRs. 10 is a plan view showing a layout of an electrostatic discharge protection element described in Patent Document 4. FIG. It is sectional drawing by the BB line shown in FIG. It is sectional drawing which shows the electrostatic discharge protection element of patent document 10. It is sectional drawing which shows the electrostatic discharge protection element of patent document 8. It is sectional drawing which shows the conventional holding voltage adjustment type | mold SCR. It is a figure which shows the layout of the electrostatic protection element of patent document 7. FIG. (A) is sectional drawing by the CC line shown in FIG. 35, (b) is sectional drawing by the DD line | wire shown in FIG. It is sectional drawing which shows the other Example of the electrostatic discharge protection element of patent document 7.

Explanation of symbols

1: P ⁺ semiconductor substrate 2, 21, 21a, 21b, 62: N well 3, 3a, 3b, 20a, 20b: P well 4, 7, 10: P ⁺ region 5, 5a, 5b, 9: N ⁺ region 11: Horizontal NPN bipolar element 12: Vertical PNP bipolar element 22: P ⁺ layer (guard ring for preventing latch-up)
23, 23a, 23b: N ⁺ layer (N-well potential fixing electrode)
24: N ⁺ layer (for trigger current supply)
25, 64: P ⁺ layer (anode)
26, 26a, 26b: P ⁺ layer (for trigger current supply)
27, 27a, 27b, 65: N ⁺ layer (cathode)
28: Source 29: Drain 8, 30, 68: Gate electrode 31: P ⁺ layer (P well potential fixing electrode)
32, 63: N + layer (for contact formation)
33, 40: NMOS transistor 35: Contact 36: Distance between anode and N-well edge 37: Trigger layer width 38: Metal 41: Diode connected in series 42; P ⁺ layer for diode 43; N ⁺ layer for diode 51: Pad 52 53: Resistance element 60: Silicide 61: Silicide unformed region 66: P ⁺ layer (substrate contact)
67: STI (shallow trench isolation)

Claims (36)

A first conductivity type substrate or a first conductivity type layer;
A second conductivity type well and a first first conductivity type well formed adjacent to each other on the surface of the first conductivity type substrate or the first conductivity type layer;
A second first conductivity type well formed on a surface of the first conductivity type substrate or the first conductivity type layer;
A first high concentration second conductivity type region, a second high concentration second conductivity type region, and a first high concentration first conductivity type region formed on a surface of the second conductivity type well;
A third high-concentration second conductivity type region formed on the surface of the first first conductivity type well;
A second high-concentration first conductivity type region formed on the surface of the second first conductivity type well;
Have
The first high concentration second conductivity type region and the first high concentration first conductivity type region are connected to a first power source,
The third high-concentration second conductivity type region and the second high-concentration first conductivity type region are connected to a second power source having a potential different from that of the first power source,
The second high concentration second conductivity type region is connected to a trigger current supply circuit;
The trigger current supply circuit includes a MOS transistor connected between the second high concentration second conductivity type region and the second power supply,
A first bipolar element comprising the first high-concentration first conductivity type region, the second conductivity type well and the first conductivity type substrate or the first conductivity type layer; the second conductivity type well; The second bipolar element constituted by one conductivity type substrate or the first conductivity type layer and the third high concentration second conductivity type region cooperates to function as a thyristor;
The first high concentration first conductivity type region and the third high concentration second conductivity type region are adjacent to each other.
An electrostatic discharge protection element characterized by that. A first conductivity type substrate or a first conductivity type layer;
A second conductivity type well and a first first conductivity type well formed adjacent to each other on the surface of the first conductivity type substrate or the first conductivity type layer;
A second first conductivity type well formed on a surface of the first conductivity type substrate or the first conductivity type layer;
A first high concentration second conductivity type region, a second high concentration second conductivity type region, and a first high concentration first conductivity type region formed on a surface of the second conductivity type well;
A third high-concentration second conductivity type region formed on the surface of the first first conductivity type well;
A second high-concentration first conductivity type region formed on the surface of the second first conductivity type well;
Have
The first high concentration second conductivity type region and the first high concentration first conductivity type region are connected to a first power source,
The third high-concentration second conductivity type region and the second high-concentration first conductivity type region are connected to a second power source having a potential different from that of the first power source,
The second high concentration second conductivity type region is connected to a trigger current supply circuit;
The trigger current supply circuit includes a series diode connected between the second high concentration second conductivity type region and the second power source;
A first bipolar element comprising the first high-concentration first conductivity type region, the second conductivity type well and the first conductivity type substrate or the first conductivity type layer; the second conductivity type well; The second bipolar element constituted by one conductivity type substrate or the first conductivity type layer and the third high concentration second conductivity type region cooperates to function as a thyristor;
The first high concentration first conductivity type region and the third high concentration second conductivity type region are adjacent to each other.
An electrostatic discharge protection element characterized by that. A first conductivity type substrate or a first conductivity type layer;
A second conductivity type well and a first first conductivity type well formed adjacent to each other on the surface of the first conductivity type substrate or the first conductivity type layer;
A second first conductivity type well formed on a surface of the first conductivity type substrate or the first conductivity type layer;
A first high concentration second conductivity type region, a second high concentration second conductivity type region, and a first high concentration first conductivity type region formed on a surface of the second conductivity type well;
A third high-concentration second conductivity type region formed on the surface of the first first conductivity type well;
A second high-concentration first conductivity type region formed on the surface of the second first conductivity type well;
Have
The first high concentration second conductivity type region and the first high concentration first conductivity type region are connected to a first power source,
The third high-concentration second conductivity type region and the second high-concentration first conductivity type region are connected to a second power source having a potential different from that of the first power source,
The second high concentration second conductivity type region is connected to a trigger current supply circuit;
The trigger current supply circuit includes a MOS transistor connected between the second high concentration second conductivity type region and the second power supply,
A first bipolar element comprising the first high concentration first conductivity type region, the second conductivity type well and the first conductivity type substrate or the first conductivity type layer; the second conductivity type well; The second bipolar element constituted by one conductivity type substrate or the first conductivity type layer and the third high concentration second conductivity type region cooperates to function as a thyristor;
The second high concentration second conductivity type region and the third high concentration second conductivity type region are adjacent to each other.
An electrostatic discharge protection element characterized by that. A first conductivity type substrate or a first conductivity type layer;
A second conductivity type well and a first first conductivity type well formed adjacent to each other on the surface of the first conductivity type substrate or the first conductivity type layer;
A second first conductivity type well formed on a surface of the first conductivity type substrate or the first conductivity type layer;
A first high concentration second conductivity type region, a second high concentration second conductivity type region, and a first high concentration first conductivity type region formed on a surface of the second conductivity type well;
A third high-concentration second conductivity type region formed on the surface of the first first conductivity type well;
A second high-concentration first conductivity type region formed on the surface of the second first conductivity type well;
Have
The first high concentration second conductivity type region and the first high concentration first conductivity type region are connected to a first power source,
The third high-concentration second conductivity type region and the second high-concentration first conductivity type region are connected to a second power source having a potential different from that of the first power source,
The second high concentration second conductivity type region is connected to a trigger current supply circuit;
The trigger current supply circuit includes a series diode connected between the second high concentration second conductivity type region and the second power source;
A first bipolar element comprising the first high concentration first conductivity type region, the second conductivity type well and the first conductivity type substrate or the first conductivity type layer; the second conductivity type well; The second bipolar element constituted by one conductivity type substrate or the first conductivity type layer and the third high concentration second conductivity type region cooperates to function as a thyristor;
The second high concentration second conductivity type region and the third high concentration second conductivity type region are adjacent to each other.
An electrostatic discharge protection element characterized by that. The first high-concentration second conductivity type region and the second high-concentration second conductivity type region each include a plurality of divided regions,
The divided regions of the first high-concentration second conductivity type region and the second high-concentration second conductivity type region are divided between the second high-concentration first conductivity type region and the third high-concentration second conductivity type region. It is alternately arranged in the direction orthogonal to the facing direction,
The first high concentration first conductivity type region extends between the divided regions,
The electrostatic discharge protection element according to any one of claims 1 to 4, wherein the electrostatic discharge protection element is provided. The first high-concentration second conductivity type region is divided into two parts and is separated in a direction orthogonal to the opposing direction of the second high-concentration first conductivity type region and the third high-concentration second conductivity type region. And
The second high-concentration second conductivity type region is disposed between the divided regions of the first high-concentration second conductivity type region, and the divided region of the first high-concentration second conductivity type region and the second high-concentration second region. The first high-concentration first conductivity type region extends between the conductivity type regions,
The electrostatic discharge protection element according to any one of claims 1 to 4, wherein the electrostatic discharge protection element is provided. The third high-concentration second conductivity type region is divided into two parts and arranged apart in a direction orthogonal to the opposing direction of the second high-concentration first conductivity type region and the third high-concentration second conductivity type region. And
The second conductivity type well extends between the divided regions of the third high concentration second conductivity type region;
The second high-concentration second conductivity type region is disposed in an extension region of the second conductivity type well.
The electrostatic discharge protection element according to any one of claims 1 to 4, wherein the electrostatic discharge protection element is provided. The first high-concentration second conductivity type region and the third high-concentration second conductivity type region are each divided into two so that the second high-concentration first conductivity type region and the third high-concentration second conductivity-type region are divided. It is arranged away in the direction orthogonal to the facing direction,
The second conductivity type well extends between the divided regions of the third high concentration second conductivity type region;
The second high-concentration second conductivity type region is disposed in the extension region of the second conductivity type well, and the first high-concentration first conductivity type region is the first high-concentration second conductivity type region. Extending between the divided areas,
The electrostatic discharge protection element according to any one of claims 1 to 4, wherein the electrostatic discharge protection element is provided. The first high-concentration second conductivity type region is divided into two parts and is separated in a direction orthogonal to the opposing direction of the second high-concentration first conductivity type region and the third high-concentration second conductivity type region. And
The first high-concentration first conductivity type region has a portion near the third high-concentration second conductivity type region at the center in the dividing direction of the first high-concentration second conductivity type region.
The second high-concentration second conductivity type region is disposed in the notch,
The electrostatic discharge protection element according to any one of claims 1 to 4, wherein the electrostatic discharge protection element is provided. A second conductivity type well and a first conductivity type well formed on the surface of the first conductivity type substrate or the first conductivity type layer;
A first high concentration second conductivity type region, a second high concentration second conductivity type region, and a first high concentration first conductivity type region formed on a surface of the second conductivity type well;
A third high-concentration second conductive type region and a third high-concentration first conductive type region formed on the surface of the first conductive type well;
Have
The first high concentration second conductivity type region and the first high concentration first conductivity type region are connected to a first power source,
The third high-concentration second conductivity type region is connected to a second power source having a potential different from that of the first power source;
The second high concentration second conductivity type region and the third high concentration first conductivity type region are connected via a series diode,
A first bipolar element comprising the first high concentration first conductivity type region, the second conductivity type well and the first conductivity type substrate or the first conductivity type layer; the second conductivity type well; The second bipolar element constituted by one conductivity type substrate or the first conductivity type layer and the third high concentration second conductivity type region cooperates to function as a thyristor;
The second high concentration second conductivity type region and the third high concentration second conductivity type region are adjacent to each other.
An electrostatic discharge protection element characterized by that. A first conductivity type substrate or a first conductivity type layer;
A second conductivity type well and a first first conductivity type well formed adjacent to each other on the surface of the first conductivity type substrate or the first conductivity type layer;
A second first conductivity type well formed on the surface of the first conductivity type substrate or the first conductivity type layer;
A first high concentration second conductivity type region, a second high concentration second conductivity type region, and a first high concentration first conductivity type region formed on a surface of the second conductivity type well;
A third high concentration second conductivity type region and a third high concentration first conductivity type region formed on the surface of the first first conductivity type well;
A second high-concentration first conductivity type region formed on the surface of the second first conductivity type well;
Have
The first high concentration second conductivity type region and the first high concentration first conductivity type region are connected to a first power source,
The third high-concentration second conductivity type region and the second high-concentration first conductivity type region are connected to a second power source having a potential different from that of the first power source,
The second high concentration second conductivity type region and the third high concentration first conductivity type region are connected via a series diode,
A first bipolar element comprising the first high concentration first conductivity type region, the second conductivity type well and the first conductivity type substrate or the first conductivity type layer; the second conductivity type well; The second bipolar element constituted by one conductivity type substrate or the first conductivity type layer and the third high concentration second conductivity type region cooperates to function as a thyristor;
The second high concentration second conductivity type region and the third high concentration second conductivity type region are adjacent to each other.
An electrostatic discharge protection element characterized by that. The third high-concentration second conductivity type region is divided into two parts and arranged apart in a direction orthogonal to the opposing direction of the second high-concentration first conductivity type region and the third high-concentration second conductivity type region. And
The second conductivity type well extends between the divided regions of the third high concentration second conductivity type region;
The second high-concentration second conductivity type region is disposed in an extension region of the second conductivity-type well, and the third high-concentration first conductivity type region is divided into two parts, so that the first high-concentration first Disposed outside the opposing region of the conductive type region and the third high concentration second conductive type region,
The electrostatic discharge protection element according to claim 11. The second conductivity type well extends to the back of a region opposite to the divided region of the third high concentration first conductivity type region and the second high concentration second conductivity type region;
The electrostatic discharge protection element according to claim 12. The width of the second high-concentration second conductivity type region is a minimum width capable of forming a contact within a range allowed by a design rule.
The electrostatic discharge protection element according to any one of claims 1 to 13, wherein the electrostatic discharge protection element is provided. A P-type substrate or a P-type layer;
An N-well formed on the surface of the P-type substrate or P-type layer;
A first high concentration N-type region, a second high concentration N-type region, and a first high concentration P-type region formed on the surface of the N well;
A third high-concentration N-type region, a second high-concentration P-type region, and a third high-concentration P-type region formed on the surface of the P-type substrate or P-type layer;
A first resistance element connected between the first high-concentration P-type region and the second high-concentration N-type region;
A second resistance element connected between the second high-concentration P-type region and the third high-concentration P-type region;
Have
The first high concentration N-type region and the first high concentration P-type region are connected to a first power source,
The third high-concentration N-type region and the second high-concentration P-type region are connected to a second power source having a potential different from that of the first power source,
The second high concentration N-type region is connected to a trigger current supply circuit,
The first bipolar element constituted by the first high-concentration P-type region, the N-well and the P-type substrate or the P-type layer, the N-well, the P-type substrate or the P-type layer, and the third high It functions as a thyristor in cooperation with the second bipolar element constituted by the concentration N-type region,
The second high concentration N-type region and the third high concentration N-type region are adjacent to each other.
An electrostatic discharge protection element characterized by that. The width of the second high-concentration N-type region is a minimum width that can form a contact within a range allowed by a design rule.
The electrostatic discharge protection element according to claim 15. A first conductivity type substrate or a first conductivity type layer;
A second conductivity type well and a first conductivity type well formed adjacent to each other on the surface of the first conductivity type substrate or the first conductivity type layer;
A first high concentration second conductivity type region, a first high concentration first conductivity type region, and a second high concentration first conductivity type region formed on a surface of the second conductivity type well;
A second high concentration second conductive type region and a third high concentration first conductive type region formed on a surface of the first conductive type well;
Have
The first high concentration second conductivity type region and the first high concentration first conductivity type region are connected to a first power source;
The second high-concentration second conductivity type region and the third high-concentration first conductivity type region are connected to a second power source having a potential different from that of the first power source,
The second high concentration first conductivity type region is connected to a trigger current supply circuit;
A first bipolar element comprising the first high-concentration first conductivity type region, the second conductivity type well and the first conductivity type substrate or the first conductivity type layer; the second conductivity type well; A first conductivity type substrate or the second bipolar element constituted by the first conductivity type layer and the second high-concentration second conductivity type region cooperates to function as a thyristor;
The second high concentration first conductivity type region and the second high concentration second conductivity type region are adjacent to each other,
An electrostatic discharge protection element characterized by that. The first high-concentration second conductivity type region and the first high-concentration first conductivity type region are each divided into a plurality of portions, and the first high-concentration second conductivity type region and the first high-concentration first conductivity type. It is arranged away in the direction orthogonal to the facing direction of the area,
The second high concentration first conductivity type region extends between the divided regions,
The electrostatic discharge protection element according to claim 17. In the second high-concentration first conductivity type region, a portion extending between the divided regions has a minimum width capable of forming a contact within a range allowed by a design rule,
The part other than the part extending between the divided areas is less than the minimum width,
The electrostatic discharge protection element according to claim 18. A first conductivity type substrate or a first conductivity type layer;
A second conductivity type well and a first conductivity type well formed adjacent to each other on the surface of the first conductivity type substrate or the first conductivity type layer;
A first high concentration first conductive type region and a first high concentration second conductive type region formed on a surface of the second conductive type well;
A second high concentration second conductive type region and a second high concentration first conductive type region formed on the surface of the first conductive type well;
Have
The first high-concentration first conductivity type region is connected to a first power source;
The second high-concentration second conductivity type region and the second high-concentration first conductivity type region are connected to a second power source having a potential different from that of the first power source,
The first high concentration second conductivity type region is connected to a trigger current supply circuit;
A first bipolar element comprising the first high-concentration first conductivity type region, the second conductivity type well and the first conductivity type substrate or the first conductivity type layer; the second conductivity type well; The second bipolar element constituted by one conductivity type well and the first high concentration second conductivity type region cooperates to function as a thyristor;
The first high concentration second conductivity type region and the second high concentration second conductivity type region are adjacent to each other,
The first high-concentration first conductivity type region is divided into a plurality of portions, and is separated in a direction orthogonal to the opposing direction of the second high-concentration second conductivity type region and the second high-concentration first conductivity type region. Has been placed,
The first high-concentration second conductivity type region extends between the divided regions.
An electrostatic discharge protection element characterized by that. The first high-concentration second conductivity type region has a minimum width capable of forming a contact within a range allowed by a design rule.
The electrostatic discharge protection element according to claim 20. Of the first high-concentration second conductivity type region, a portion other than the portion extending between the divided regions is less than the minimum width.
The electrostatic discharge protection element according to claim 21. A region where no silicide is formed is provided between adjacent high concentration regions,
The electrostatic discharge protection element according to any one of claims 1 to 22, A gate electrode is provided between adjacent high concentration regions,
The electrostatic discharge protection element according to any one of claims 1 to 22, A first conductivity type substrate or a first conductivity type layer;
A second conductivity type well and a first conductivity type well formed adjacent to each other on the surface of the first conductivity type substrate or the first conductivity type layer;
A first high concentration second conductive type region and a first high concentration first conductive type region formed on a surface of the second conductive type well;
A second high concentration first conductive type region and a second high concentration second conductive type region formed on the surface of the first conductive type well;
Have
The second conductivity type well and the first conductivity type well are connected to a trigger current supply circuit,
A first bipolar element constituted by the first high concentration first conductivity type region, the second conductivity type well and the first conductivity type substrate or the first conductivity type layer, and the first high concentration second conductivity type. A second bipolar element configured by the region, the first high concentration first conductivity type region and the second high concentration second conductivity type region, functions as a thyristor;
The second high concentration first conductivity type region and the second high concentration second conductivity type region are adjacent to each other,
A current flows simultaneously in each well of each of the bipolar elements,
An electrostatic discharge protection element characterized by that. A first conductivity type substrate or a first conductivity type layer;
A second conductivity type well and a first conductivity type well formed on the surface of the first conductivity type substrate or the first conductivity type layer;
A first electrode of a first conductivity type formed on a surface of the second conductivity type well;
A first high concentration second conductivity type region formed on the surface of the second conductivity type well and applied with the same potential as the first electrode;
A second high concentration second conductivity type region formed on the surface of the second conductivity type well and connected to the trigger element;
A second conductivity type second electrode formed on the surface of the first conductivity type well;
A first high-concentration first conductivity type region formed on the surface of the first conductivity type well and applied with the same potential as the first electrode;
Have
The first high-concentration first conductivity type region is disposed at a position deviating from a region where the first electrode and the second electrode are opposed to each other,
A first bipolar element composed of the first conductivity type substrate or first conductivity type layer, the second conductivity type well and the first electrode; the second conductivity type well; the first conductivity type substrate; The second bipolar element constituted by the first conductivity type layer and the second electrode cooperates to function as a thyristor,
A trigger current flows in the second conductivity type well;
An electrostatic discharge protection element characterized by that. A second high-concentration first conductivity type region is provided on the surface of the first conductivity type well,
The second high concentration first conductivity type region is connected to the trigger element.
27. The electrostatic discharge protection element according to claim 26. A first bipolar element and a second bipolar element that cooperate to function as a thyristor;
A trigger device for the first bipolar element and the second bipolar devices operated simultaneously,
A first resistance element;
A second resistance element;
With
One end of the trigger element is connected to the base region of the first bipolar element via the first resistance element,
The other end of the trigger element is connected to the base region of the second bipolar element via the second resistance element, and is grounded via the second resistance element.
An electrostatic discharge protection circuit characterized by that. A first well of a first conductivity type comprising a first region of a first conductivity type and a second region of a second conductivity type;
A second well of the second conductivity type comprising a third region of the first conductivity type and a fourth region of the second conductivity type;
A trigger element;
Resistance,
With
The first bipolar element constituted by the first well, the second region and the second well and the second bipolar element constituted by the first well, the second well and the third region are cooperative. Working as a thyristor,
One end of the trigger element is connected to the first region,
The other end of the trigger element is connected to the fourth region ;
One end of the resistor is connected to the first region,
The other end of the resistor is connected to the second region;
The trigger element is Ru actuates said first bipolar element and the second bipolar elements simultaneously,
An electrostatic discharge protection circuit characterized by that. Further comprising a pad,
The pad being connected to said first region through said resistor,
The one end of the trigger element is connected to the second region through the resistor,
30. The electrostatic discharge protection circuit according to claim 29 . Further comprising a second resistor,
Wherein the trigger element and the other end is connected to said third region via said second resistor, and is grounded via said second resistor,
30. The electrostatic discharge protection circuit according to claim 29 . The first region and the second region are configured not to interfere with each other by an insulating region formed therebetween.
30. The electrostatic discharge protection circuit according to claim 29 . The third region and the fourth region are configured not to interfere with each other by an insulating region formed therebetween.
30. The electrostatic discharge protection circuit according to claim 29 . A first bipolar element and a second bipolar element that cooperate to function as a thyristor;
A trigger device for the first bipolar element and the second bipolar devices operated simultaneously,
And a resistance element,
With
Emitter region of said first bipolar element is connected via a front Ki抵 anti element to the base region of said first bipolar element,
One end of the trigger element is connected to a base region of the first bipolar element;
The other end of the trigger element is connected to a base region of the second bipolar element;
An electrostatic discharge protection circuit characterized by that. A first bipolar element and a second bipolar element that cooperate to function as a thyristor;
A trigger device for the first bipolar element and the second bipolar devices operated simultaneously,
And a resistance element,
With
One end of the trigger element is connected to a base region of the first bipolar element;
The other end of the trigger element is connected to a base region of the second bipolar element;
Base region of said second bipolar device is grounded via the front Ki抵 anti element,
An electrostatic discharge protection circuit characterized by that. A first bipolar element and a second bipolar element that cooperate to function as a thyristor;
A trigger device for the first bipolar element and the second bipolar devices operated simultaneously,
And a resistance element,
With
One end of the trigger element is connected to a base region of the first bipolar element;
The other end of the trigger element is connected via a front Ki抵 anti element to the base region of the second bipolar element,
An electrostatic discharge protection circuit characterized by that.

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