JPH0760891B2 - Semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is a current control type semiconductor switch element having negative resistance characteristics, and a combination thereof can perform a shift register, a memory, a logical function and the like. The present invention relates to a possible semiconductor device.

[Conventional technology]

Conventionally, unijunction transistors (UJT,
Double base diodes) and thyristors (pnpn diodes) are well known as individual semiconductor devices. In addition, a plasma-coupled device (PCD: Plasma Coupled Device), which combines a number of improved UJT switches,
No. 3) has logic and shift register functions and is therefore applied to integrated circuits such as solid-state image sensors.

Fig. 7 shows a UJT with a hook.
Is a plan view, (B) is a cross-sectional view, and (C) is an electrical characteristic diagram thereof. The region 2 is an emitter diffusion region that forms a rectifying junction with the semiconductor substrate 1 made of an n-type semiconductor,
The region 3 is a base diffusion region that makes a resistive junction with the semiconductor substrate 1. Further, the diffusion region 4 forms a rectifying junction with the semiconductor substrate 1, and a region 5 having the same conductivity type as that of the semiconductor substrate 1 is formed in this region 4 to form a collector region having a hook structure. There is. In this UJT, when a constant voltage is applied between the regions 3 and 5 by the power supply 6, the current control type negative resistance shown in FIG. Here, the hook structure is used in the collector region in order to prevent the standby current from constantly flowing between the regions 3 and 5. That is, in the UJT without the hook in which the region 4 is removed, the standby current constantly flows between the regions 3 and 5, and there is a problem in low power consumption operation. Therefore, a hook structure has been conventionally used in the collector region.

[Problems to be solved by the invention]

However, in the above structure, since the regions 4 and 5 have the double diffusion structure, there is a limitation on the alignment accuracy of the photomask and the lateral spread of the impurity diffusion in the manufacturing process, and the junction region is miniaturized to increase the density. It was difficult to achieve high integration. In addition, the double diffusion structure increases the junction capacitance, resulting in a decrease in operating speed.

Further, when two types of switch elements having complementary electric characteristics are integrated on the same substrate, if a normal single crystal substrate is used, the double diffusion structure portion inevitably becomes a triple diffusion structure. I will end up. In the triple diffusion structure, since a high-concentration joint surface is formed as a matter of course, the junction capacitance further increases and the operation speed decreases. The decrease in operating speed itself is one major problem, but this is also undesirable from the viewpoint that it is difficult to match the electrical characteristics of the integrated two types of switch elements. For example, in the above-mentioned PCD, a negative polarity pulse (change from high level to low level: H → L) is normally used as a signal output, but by combining it with a signal of a positive polarity, that is, complementary It is conceivable that the degree of freedom in functional design of signal processing is increased and the performance such as high-speed operation is improved by simultaneously using the switch elements that function effectively. However, as described above, the conventional UJT structure with hooks has not been easy to realize because it is difficult to match the electrical characteristics of both types.

[Means for solving problems]

The semiconductor device of the present invention has been made in view of the above-mentioned problems, and is for providing a potential to the semiconductor substrate by forming a resistive junction with the semiconductor substrate of the first conductivity type serving as a base. A first diffusion region of the first conductivity type, a second diffusion region of the second conductivity type that forms a rectifying junction with the semiconductor substrate and serves as an emitter, and a rectifying junction with the semiconductor substrate that forms a Schottky barrier junction on its surface. Is formed, and a third diffusion region of the second conductivity type serving as a collector is formed together with the Schottky barrier junction, and the second diffusion region and the third diffusion region have an interval within the diffusion length of minority carriers. It is arranged.

[Action]

Applying a constant bias between the first diffusion region and the Schottky barrier junction on the third diffusion region is based on the minority carrier injection of the Schottky barrier junction between the second diffusion region and the Schottky barrier junction. A current controlled negative resistance can be obtained.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to Examples.

FIG. 1 shows an embodiment of the present invention. FIG. 1 (A) is a plan view, FIG. 1 (B) is a sectional view, and FIG. 1 (C) is an electric characteristic showing its current-voltage static characteristic. It is a figure. The same or corresponding parts as in FIG. 7 are designated by the same reference numerals. That is, 1 is a semiconductor substrate (however, a p-type semiconductor in this embodiment), 3 is a resistive junction region (first diffusion region) as a base for applying a substrate potential, and 2 is a minority carrier injection source. Is a rectifying junction region (second diffusion region) as an emitter. Further, 7 is a conductivity type opposite to that of the semiconductor substrate 1 and has a low concentration (for example, a surface impurity concentration at which a tunnel current hardly occurs in a Schottky barrier junction:
The collector hook region (third diffusion region) 8 of 10 ¹⁷ cm ⁻³ or less) is a Schottky metal that forms a Schottky barrier junction with the collector hook region 7, and together with the region 7 serves as a collector. The relationship between the emitter region 2, the Schottky metal 8 and the substrate 1 corresponds to the relationship between the emitter, collector and base of the lateral transistor, respectively. Therefore, the interval between the emitter region 2 and the collector hook region 7 below the Schottky metal 8 corresponds to the base width, and the smaller the interval, the higher the minority carrier transport efficiency and the steep negative resistance characteristic. Therefore, in order to substantially function as a switching element, it is preferable that the distance between the emitter region 2 and the collector hook region 7 is within the diffusion length of minority carriers. The base region 3 can also be arranged on the back surface 9 of the semiconductor substrate 1.

In order to operate this element, a constant voltage V _BC is applied between the Schottky metal 8 and the base region 3 by the bias power source 6, and the load resistor 10 and the variable voltage source are connected between the emitter region 2 and the Schottky metal 8. Connect 11 Voltage source 11
As a result of the voltage change, the current-voltage characteristic between the emitter region 2 and the Schottky metal 8 can obtain a current control type negative resistance characteristic as shown in FIG. 1 (C). However, since a p-type semiconductor is used as the semiconductor substrate 1 in this embodiment, it has a complementary relationship with the current-voltage characteristics of the conventional element using the n-type semiconductor shown in FIG. 7 as a substrate.

The current-voltage static characteristics shown in FIG. 1 (C) are the turnover voltage V _T , which is the voltage that shifts from the cut-off state to the conductive state, and the sustain voltage, which is the minimum voltage at the stable point that maintains the conductive state.
It can be represented by three parameters: Vs and sustain current Is, which is the current at that time. Of these parameters, the important one as a switching element is the turnover voltage V _T , and this turnover voltage V _T is
It is given by the relational expression of V _T = V _BC + V _D. That is, the turnover voltage V _T is determined by the bias voltage V _BC and the diffusion potential V _D of the pn junction diode formed by the region 2 and the substrate 1.

Next, the operating principle of the present invention will be described with reference to the energy band diagram of FIG. This energy band diagram is drawn along the path XX 'in FIG. 1 (B). When there is no electron injection from the emitter region 2 into the semiconductor substrate 1, the emitter region 2 and the Schottky metal 8 are in a cutoff state. This is because the emitter junction between the semiconductor substrate 1 and the emitter region 2 is reverse biased, and the potential of the collector hook region 7 is below the diffusion potential with respect to the Schottky metal 8. On the other hand, when the emitter junction is forward-biased (≧ V _BC + V _D ), electron injection into the semiconductor substrate 1 starts, and the electrons due to diffusion reach the collector hook region 7 to raise its potential and put the Schottky barrier junction in the forward-biased state. To do. As the Schottky current increases, minority carrier (hole) injection starts from the Schottky metal 8 side to the collector hook region 7 side under certain conditions, and the vicinity of the collector hook region 7 becomes a conductivity modulation state. As a result, the hook disappears, a negative resistance is generated between the emitter and collector, the cut-off state transitions to the conduction state with a low on-voltage, and the pn junction diode characteristic shown by the broken line in FIG. The characteristic curve is drawn.

By the way, the injection condition of the minority carriers in the Schottky barrier junction is obtained from the expression of injection efficiency γ (the minority carrier current with respect to the total current of the Schottky diode) γ = n _i ² j / (bN _D ² jns). Sharfetter, Solid-State Electronics, Vol.8, pp.299-311, 1965: Scharf
etter, Solid-State, Electronics, Vol.8, pp.299-311,1
965). Where n _i = intrinsic carrier density j = total current of Schottky diode jns = reverse saturation current b = μn / μp = ratio of electron field mobility μn to hole field mobility μp N _D = n type semiconductor Is the donor concentration. On the other hand, the reverse saturation current JNS is _{jns = exp (-qφ Bn / kT} ) ... relationship with. Here, q = charge amount of electrons φ _Bn = barrier value of Schottky diode k = Boltzmann constant T = absolute temperature From the above equation and equation, the condition for obtaining minority carrier injection is that the j / jns ratio becomes large,
This can be realized by reducing the Schottky junction area and using Schottky metal having a high Schottky barrier value.

As a specific example of the present embodiment, N _D = 10 ¹⁶ cm ^-3 , the junction area of the collector is 1 × 2 μm ² , Pt silicide having a high barrier value for Schottky metal, a ternary amorphous material, a−
Si-Ge-B (φ _Bn is 0.85 to 1.0 eV, jns = 3.5 × 10 ^-8 A / cm ² :
Murase et al., Journal of Applied Physics, 21 , 11, pp.1559-1565,1982)
, The collector current is 0.5mA and the injection efficiency γ is 45%.
Also reaches.

FIG. 3 is a representative example of the actual measurement results of this element, and it can be seen that the static characteristics of the switch controlled by the bias voltage V _BC can be obtained.

Further, FIG. 4 is an actual measurement example of the switching dynamic characteristics,
A collector current as shown by the solid line in the lower part of the figure is obtained for a signal input as shown by the solid line in the upper part of the figure. The broken line at the bottom of the figure shows the collector current when the same signal input is applied to the conventional UJT with hook shown in FIG.
Compared with the characteristics of this element shown by the solid line, this element clearly operates at higher speed, and the rise time is almost 3
It can be seen that the improvement is about 4 times.

FIG. 5 is a plan view showing a second embodiment of the present invention, in which a plurality of switch elements shown in FIG. 1 are arranged on the same substrate, and the input / output operation is basically the same as that of the PCD described above. Is the same. In this figure, the same or corresponding parts as in FIG. 1 are designated by the same reference numerals. In this embodiment, the base region 3 forming a resistive junction with the semiconductor substrate 1 surrounds another diffusion region group on the main surface. The base region 3 may be formed on the peripheral surface and the bottom surface in addition to the main surface. The diffusion region 12 is a region that forms a resistive junction with the semiconductor substrate 1, and functions as an electrode for extracting the substrate potential in the vicinity of the Schottky metal 8. The diffusion region 13 is a rectifying junction region,
It is connected to the signal input terminal 17. Then, the regions 2 and 12, the Schottky metal 8 and the collector hook region (not shown) therebelow form a block 14 which is an element of one unit.

In order to operate the apparatus of this embodiment configured as described above as a scanner, a constant bias is applied between the Schottky metal 8 and the diffusion region 3 by the power source 6, and the region 2 of each block is supplied.
When a periodic clock pulse (however, the phases given to the blocks adjacent to each other are shifted by a predetermined relationship) is applied, the ON / OFF state of the adjacent blocks affects the turn-on voltage and is applied to the region 13. The signals are sequentially transferred in synchronization with the clock pulse. Then, this signal can be extracted from the diffusion region 12 of each block. In this embodiment, if the conductivity type of the substrate 1 is p-type,
The signal output at this time is a positive polarity pulse from L to H,
The polarity is complementary to the existing PCD.

FIG. 6 is a sectional view showing a third embodiment of the present invention, in which a conventional UJT with a hook and an element of the present invention are integrated on the same substrate. In the figure, the same or corresponding parts as those in FIGS. 1 and 7 are designated by the same reference numerals. On the main surface of the semiconductor substrate 1 of n-type conductor, a conventional UJT 15 with a hook including an emitter region 2, a base region 3 and regions 4 and 5 forming a collector region is formed. Similarly, a well 1'of a p-type conductor is formed on the main surface of the semiconductor substrate 1, and an emitter region 2, a base region 3 and a collector hook region 7 are formed in the well 1 '. The switching element according to the present invention is configured with the Schottky metal 8 formed in the above. With this structure, switch elements having electrical characteristics complementary to each other can be formed on the same substrate without using a triple diffusion structure.

〔The invention's effect〕

As described above, according to the semiconductor device of the present invention, the first diffusion layer of the first conductivity type for applying a potential to the semiconductor body of the first conductivity type serving as the base and the first diffusion layer of the second conductivity type serving as the collector. By applying a constant bias between the diffusion region of No. 3 and the Schottky barrier junction thereabove, a small number of Schottky barrier junctions are formed between the second diffusion region of the second conductivity type serving as the emitter and the Schottky barrier junction. Since a current control system negative resistance based on carrier injection is obtained, it can function as a switch element having a latch function. Then, it is easy to form the third diffusion region shallow by ion implantation and to make the Schottky barrier junction depth a structure of several hundred Å or less. In other words, the pn of the double diffusion structure by the impurity thermal diffusion method such as the collector of UJT with a hook which has been conventionally used as a switch element having a latch function.
Compared with the junction structure, the Schottky barrier junction of the present invention can be easily miniaturized, and is advantageous as a basic element of a high density and highly integrated LSI element. In addition, the fact that the Schottky barrier junction area can be reduced means that the junction capacitance can be reduced, which is effective for speeding up the switching operation. Furthermore, unlike the case of the pn junction, the minority carrier injection in the Schottky barrier junction is an injection amount limited by the barrier value of the Schottky metal, so it is not transferred to deep saturation. Such shallow saturation operation is extremely advantageous for high-speed switching as well as being able to reduce the Schottky barrier junction area. Further, according to the present invention, there is an advantage that two types of switch elements having complementary characteristics can be easily manufactured on the same substrate without using a triple diffusion structure.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1A is a plan view, FIG. 1B is a sectional view, and FIG.
Is an electric characteristic diagram showing the current-voltage static characteristic, and FIG. 2 is an energy band diagram along the path XX ′ in FIG. 1 (B).
FIG. 3 shows the static characteristics of the embodiment of FIG. 1, and is a graph of the measured values of the dependence of each parameter on the bias voltage V _BC . FIG. 4 shows the measured values of the switching response characteristics of the embodiment of FIG. 5 is a plan view showing a second embodiment of the present invention, FIG. 6 is a sectional view showing a third embodiment of the present invention, and FIG. 7 is a conventional UJT with a hook. And
The figure (A) is a plan view, the figure (B) is a sectional view, and the figure (C).
FIG. 4 is an electrical characteristic diagram showing the current-voltage static characteristic. 1 ... Semiconductor substrate, 2 ... Emitter diffusion region, 3, 9 ...
Base diffusion area, 4 …… Collector hook area, 8 …… Schottky metal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-49-115684 (JP, A) JP-A-60-160782 (JP, A) JP-A-60-196972 (JP, A) JP-B-53- 13953 (JP, B2)

Claims (1)

[Claims] 1. A first diffusion region of a first conductivity type for forming a resistive junction with the semiconductor substrate of a first conductivity type, which serves as a base, for applying an electric potential to the semiconductor substrate, and the semiconductor. A second diffusion region of the second conductivity type that forms a rectifying junction with the substrate and serves as an emitter, and a Schottky barrier junction that forms a rectifying junction with the semiconductor substrate and is formed on the surface thereof and forms a collector together with the Schottky barrier junction. A third diffusion region of the second conductivity type is formed, and the second diffusion region and the third diffusion region are arranged with an interval within a diffusion length of minority carriers. apparatus.