JPS592189B2 - reverse conducting thyristor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a new structure for a high-performance reverse conduction thyristor that can control large amounts of power at high speed.

Reverse conduction thyristors are mainly used in various inverter and chopper fields, including vehicle choppers. As practical research in these fields progresses, there has been a strong demand for an increase in the control power of reverse conduction thyristors9, and for this purpose, it has become inevitable to increase the diameter of semiconductor wafers. However, in the design and manufacture of reverse conduction thyristors, when the diameter of the semiconductor wafer decreases, fundamental problems that affect device performance arise, and simply increasing the wafer diameter does not allow for a given increase in control power. It is difficult to realize this. In other words, the crystal defects and crystal strain that occur in semiconductor wafers during heat treatment processes such as diffusion tend to be more unevenly distributed as the wafer becomes larger in diameter.Therefore, thyristors with a large diameter are resistant to most of the characteristics of reverse conduction thyristors. Accurate control of the affected carrier lifetime becomes very difficult.

Conventional Example FIG. 1 shows a cross section of a typical example of a reverse conduction thyristor manufactured by the United States.

The plane is rotationally symmetrical. The conventional reverse conduction thyristor shown in FIG. 2 base layer PB and its surface, i.e. the second
An n-shaped secondary
Four layers of the emitter layer NE are made adjacent to each other in order, and a first Pn junction J1, a second Pn junction J2, and a third Pn junction are formed between them.
It constitutes an n-junction J3. The lower part of the annular n-type second emitter layer constitutes a thyristor part 11, and the surrounding part consisting of the first base layer NB and second base layer PB constitutes a diode part 12, both of which are arranged in antiparallel. For this reason, it is built into the reverse conduction thyristor wafer 13. An annular fourth emitter layer Ng is provided inside the second emitter layer NE and is spaced apart from the second emitter layer NE, and is connected to the second base layer PB by joining J4.
have. The first of this reverse conduction thyristor wafer 15
A first main electrode, which will become an anode electrode 17 such as an MO plate, is generally alloy-brazed to the main surface 16 via a thin layer of A1 or AlSi, and this also serves as a support plate. On the other hand, the thyristor portion 11 of the second main surface 18
A ring-shaped cathode main electrode 19 is provided in common to the diode portion 12 and a gate electrode 21 is provided in the central part of the second main surface 18 where the second base layer PB is exposed. An auxiliary thyristor electrode 20 is provided on the annular fourth emitter layer n-bi at a position closer to the thyristor portion 11. Second main electrode 1 for naori sorting
9. The gate electrode 21 is usually formed of a vapor deposited layer such as A1. As described above, in the reverse conduction thyristor wafer 15, an arrangement structure in which the gate electrode 21 is provided in the center, the auxiliary thyristor portion 13 and the main thyristor portion 11 outside the gate electrode, and the diode portion 12 on the outermost side has been most commonly used.

The reason for this is that in order to increase the width of the turn-on region v, it is necessary to place the gate electrode in the center of the semiconductor wafer (
The center gate structure is the most advantageous, and the thyristor part is necessarily placed around it.9 Also, with the center gate structure, the device structure can be made rotationally symmetrical, so the manufacturing process, especially electrode formation and assembly, can be improved. This means that the workability is good in this process, and it is easy to obtain a corresponding increase in manufacturing yield and high reliability. However, semiconductor wafers have large diameters, especially 5011m? At the upper diameter, this structure presents the following problems.

Generally, when a semiconductor wafer is heat-treated by impurity diffusion, oxide film formation, etc., many crystal defects are likely to occur, especially near the periphery of the semiconductor wafer. It has been known that this phenomenon becomes more pronounced as the diameter increases, making it difficult to uniformly introduce crystal defects throughout the wafer. For this reason, the first
In the conventional structure example shown in the figure, more crystal defects occur in the diode portion 12 than in the thyristor portion 11, so that the carrier life due to the crystal defects is shorter than that in the thyristor portion 11.
It is long in the diode portion 12 and short in the diode portion 12. In addition, reverse conduction thyristors are often used for high-speed switching and require a short turn-off time, so a process has been introduced to control carrier life using heavy metal diffusion methods such as gold, radiation irradiation methods, and heat treatment methods. be done. However, the effects of these methods are closely dependent on crystal defects, and under the above-mentioned non-uniform distribution of crystal defects, the non-uniformity of the carrier life is further exacerbated. Therefore, in the characteristics of the obtained reverse conduction thyristor, the carrier life of the thyristor portion 11 provided near the center is not significantly shortened. For this reason, even though the turn-off time of the reverse conduction circuit is not so shortened, the carrier life of the diode portion 12 provided at the other peripheral portion is still necessary. It becomes shorter at the top. As a result, leakage current in the diode portion increases, resulting in a fundamental problem of lowering the withstand voltage. The present invention eliminates the drawbacks of conventional thyristors and develops a new element structure to obtain a reverse conduction thyristor that uses a large diameter semiconductor wafer and has both high-speed switching performance and high voltage resistance. This is what we are trying to provide.

A feature of the present invention is that the gate region, thyristor section, and diode section that constitute the reverse conduction thyristor are arranged in a new manner on the wafer, and the main thyristor section is placed inside the outer peripheral area of the semiconductor wafer, and the diode section is further placed inside the auxiliary thyristor section. By arranging the thyristor part and the gate region in the central region, the crystal defects that often occur in the outer peripheral region of the wafer can be effectively utilized to improve the characteristics of the thyristor part, and by placing the gate in the center, the aforementioned turn-on region can be improved. The characteristics of the center gate structure, such as rapid expansion, are fully utilized, and leakage of reactive current from the auxiliary thyristor electrode to the second base layer of the diode portion is prevented, and turn-on by the auxiliary thyristor is effectively performed. This is how it was done.

Next, the present invention is shown in Fig. 2a? An example shown below will be described.

A feature of the present invention is that there is no power dissipation from an electric path provided across the second base layer to the second base layer, such as an electric path connecting an auxiliary thyristor electrode and a gate auxiliary electrode provided intricately within the thyristor portion. The purpose is to prevent leakage of current.
The purpose of increasing the impedance of the leakage circuit is to provide an insulating layer between the crossing circuit and the second base layer.

? The present invention will now be described in detail with reference to embodiments. In the first embodiment of the present invention, the diameter is 60 mm and the specific resistance is 130 to 150 Ω.
? An inverted threaded thyristor is manufactured on a silicon wafer using known manufacturing methods such as a diffusion method, an epitaxial method, and a metallization method. Its structure is shown in a plan view in FIG. 2a and in side views in FIGS. 2b and 2c. Figure 2a b-b
A cross-sectional view taken along the cut plane is FIG. 2b, and a cross-sectional view taken along the a-a line is FIG. 2c. As shown in the above figures, in this embodiment, an n-type first layer NB is formed on a wafer 105.
An n+ type layer is provided on the main surface side, an annular p type first emitter layer PE is provided on the outer periphery, a p type third emitter layer is provided in the center, and a p type emitter layer is provided in contact with the first base layer NB. A second base layer PB is provided, an annular n-type second emitter layer NE is provided on its outer periphery, and an annular fourth emitter layer NE' is provided in the center.

However, there are two arc-shaped cutouts 11 in the second emitter layer NE.
5 and a radial cutout 116 extending from a portion of each arc toward the center of the wafer. In the reverse conduction thyristor, the first emitter layer PE, the n+ layer, the first base layer NB, the second base layer PB, and the second emitter layer NE in the peripheral part constitute the main thyristor part 1, and inside thereof, the n+ The layers, the first base layer NB, and the second base layer PB constitute the diode portion 102, and inside thereof, the third emitter layer Pj, the n+ layer, the first base layer NB, the second base layer PB, and the fourth emitter layer The n-bi constitutes the auxiliary thyristor portion 104.

Furthermore, the second base layer PB, the first base layer NB, and the n+ layer directly under the gate electrode 109 provided in the central part are the gate region 10.
3. The n+ layer is a layer having a higher impurity concentration than the first base layer NB9, and by providing this layer, the reverse conduction thyristor is equivalently made into a well-known Pin structure,
It is possible to reduce the thickness of the second base layer NB, which is a high resistivity layer, and to reduce the on-state voltage without impairing the withstand voltage.

This n+ layer is usually provided by epitaxial growth. First main surface 1 of the above composite thyristor wafer 105
06, the anode electrode 1 of the MO plate is inserted through the A1 vapor deposition layer.
A central gate electrode 109 is formed on the second main surface 108 by alloy brazing of A1, a cathode electrode 110 is provided in an annular shape on the outside thereof and has arcuate and radial openings, and a fourth emitter layer NE' is formed on the second main surface 108 by alloy brazing. An auxiliary thyristor electrode 111 provided in an annular shape, a gate auxiliary electrode Jl2 provided in the arc-shaped opening, and an auxiliary thyristor electrode 111 and a gate auxiliary electrode 112 through the radial opening.
Electrical paths 113 are formed to connect the two.

The arcuate gate auxiliary electrode 112 is located on the arcuate cutout 115 in the second emitter layer, and the radial electrical path 113 is located on the radial cutout 116.
Here, prior to the step of forming each electrode on the second main surface, an insulating layer 114 made of SiO2, for example, is formed on the surface of the second base layer PB so as to include the place where the electric path 113 is arranged.
will be established. SiO2 is formed by a well-known method and has a thickness of 0.8
If it is set to about 1.0 μ, the dielectric breakdown voltage becomes 40 to 50 V or more, and it is possible to prevent invalid leakage current from the electric path 113 to the second base layer PB, so that the device exhibits a sufficient function in terms of operation.
A is an anode terminal connected to the anode electrode 107, K is a cathode terminal connected to the cathode electrode 110, and G is a gate terminal connected to the gate electrode 104. In the reverse conduction thyristor thus obtained, the electric path 113 → second base layer PB → second emitter layer NE → cathode electrode 110
The impedance for the reactive current in the path, that is, the reactive current generated in the diode portion 102, is the impedance of the current path 113.
→ gate auxiliary electrode 112 → second base layer PB → second emitter layer NE → cathode electrode 110 becomes significantly higher in impedance than the effective current impedance for turning on the path.

As a result, it is possible to make the above-mentioned reactive current very small and use most of the on-current of the auxiliary thyristor section 104 as the trigger current of the thyristor section 101.
In the above embodiment, SiO2 is used as the insulator layer 114, but the insulator is not limited to this, and may include organic materials such as glass and varnish, metal oxides such as AI2O, etc., which are commonly used in the semiconductor manufacturing field. Similar effects can be achieved by using other insulating materials.

FIGS. 3a and 3b are a plan view of a reverse conduction thyristor according to a second embodiment of the present invention, respectively, as seen from the cathode side, and a sectional view taken along the line a-+a in FIG. 3a.

In this reverse conduction thyristor, the arrangement order of the thyristor portion 201, diode portion 202, gate region 203, and auxiliary thyristor portion 204 from the outer periphery to the center of the wafer 210 is the same as in the first embodiment. There is also a thyristor part 201 and a diode part 20.
A separation region 205 is additionally provided between the two. In this embodiment, as in the case of the previous embodiment, it is necessary to increase the impedance of the path from the electric path 206 to the second base layer PB to the second emitter layer NE of the diode portion 202 to the cathode electrode 208. Insulating layer 2
09 is connected to the electric circuit 206 as shown by the dotted line in FIG.
and the surface of the second base layer PB located below the electric circuit on the second main surface 211 of the composite wafer 210. Since the second emitter layer XnE is not provided in the above-mentioned separation region 205, this separation region 205 is separated from the inner part of the first emitter layer PE, the n+ layer, the first base layer NB, and the second base layer PB. It has a well-known structure consisting of a PnP three-layer structure9, and has been commonly used in the past to improve the commutation ability of reverse conduction thyristors. Since this isolation region 205 has no function as either a thyristor part or a diode part, the existence of this isolation region 205 is wasteful from the standpoint of effective use of the wafer area to improve the power capacity of the device. Ta.

In this embodiment, attention is paid to this point, and this separation region 205
By providing an arcuate electrical path 206 inside the thyristor portion 201, the utilization rate of the wafer area is improved, and as can be easily seen from both figures, a large number (six in the figure) of gate auxiliary electrodes 207 are provided inside the thyristor portion 201. Insert each gate auxiliary electrode 20
7 is connected to the second emitter layer, thereby connecting the gate auxiliary electrode and the cathode electrode 2 in the thyristor part 201.
The length of the facing part of 08 was made as long as possible.

Accordingly, the rated critical on-current increase rate (Di/D
This has succeeded in improving the turn-on switching characteristics of the reverse conduction thyristor, such as improving the high frequency characteristics (t tolerance) and high frequency characteristics. It goes without saying that the present invention can sufficiently exhibit the same effect even in the case where the p-type and n-type of the reverse conduction thyristor shown in the embodiments are completely reversed.

Further, although the above embodiment shows the case where a silicon wafer is used, the effects of the present invention will not be lost even if other semiconductor wafers are used.

In the above example, it was shown that the Au diffusion method was used to shorten the turn-off time, but other metals such as heavy metal impurity diffusion methods such as Cu, pt, and zn,
It was confirmed that the same effects of the present invention as in the above-mentioned Examples were exhibited even when radiation irradiation, rapid heating and quenching, etc. were used, or when these methods were not applied.

In the second embodiment described above, Pnp is used as the isolation region.
Although the three-layer structure is used, similar effects can be obtained by using an Npn three-layer structure or other well-known separation structures. In this invention, as described in the above embodiment, the electric circuits 113, 206, etc. provided on the second base layer PB and the base layer P
Since the insulator layers 114, 209, etc. are inserted at least in part between B, in a configuration in which, for example, a thyristor part is provided on the outer periphery of the wafer and a diode part is arranged inside the thyristor part to improve turn-on characteristics and breakdown voltage, An electric line 1 is connected across the diode section or even a part of the cathode section.
13, 206, etc., there is no risk of turn-on failure due to reactive current due to the provision of this electrical path, and the desired performance can be achieved.

[Brief explanation of drawings]

Figure 1a is a cross-sectional view of an example of a conventional reverse conduction thyristor;
Figure a is a plan view of the reverse conduction thyristor according to the first embodiment of the present invention as seen from the cathode side, Figure 2b is a cross-sectional view taken along line bb in Figure 2a, and Figure 2c is a cross-sectional view taken along line a-a in Figure 2a. 3a is a plan view of the reverse conduction thyristor of the second embodiment as seen from the cathode side, and FIG. 3b is a cross-sectional view taken along the line a-a in FIG. 3a. FIG. A is the anode terminal, K is the cathode terminal, G is the gate terminal, PE is the first emitter layer, NB is the first base layer, PB is the second base layer, NE is the second emitter layer, and PE' is the third emitter layer. , Ny is the fourth emitter layer, J1 to J5 are junctions,
17, 107, 211 are anode electrodes, 19, 110,
208 is a cathode electrode, 21, 109, 212 is a gate electrode, 20, 111, 213 is an auxiliary thyristor electrode, 1
14 and 209 are electric circuits, insulating layers provided under 113 and 206, 11 and 101p201 are thyristor parts, and 20
5 is an isolation region, 12, 102, 202 is a diode portion, 13, 104, 204 is an auxiliary thyristor portion, 14,
103 and 203 are gate regions.

Claims (1)

[Claims] 1. A first emitter layer of a first conductivity type, a first base layer of a second conductivity type, a second base layer of the first conductivity type, and a second emitter layer of the second conductivity type.
A thyristor portion consisting of four layers of emitter layers adjacent to each other in sequence, a diode portion consisting of two layers of the first base layer and the second base layer, and a first conductive portion provided in a part of the first base layer. An auxiliary thyristor comprising four layers adjacent to each other in order: a third emitter layer of a type, a first base layer, a second base layer, and a fourth emitter layer of a second conductivity type provided on a part of the second base layer. a first main electrode connected to a first main surface where the first emitter layer and the first base layer are exposed; and a second main electrode opposite the first main surface; a second main electrode connected to the thyristor portion and the diode portion of the surface; a gate main electrode and a gate auxiliary electrode connected to the second base layer of the second main surface; an auxiliary thyristor electrode connected to a fourth emitter layer; and at least one connection path installed across the diode portion and spaced apart from the second main electrode, the connection path being connected to the auxiliary thyristor electrode. The thyristor electrode and the gate auxiliary electrode are electrically connected, and at least a portion of the connection path is in contact with the second base layer via an insulating layer, and the direction from the center to the periphery of the composite thyristor wafer is 1. A reverse conduction thyristor, wherein the gate electrode, the auxiliary thyristor portion, the diode portion, and the thyristor portion are arranged in this order. 2. The reverse conduction thyristor according to claim 1, wherein the insulating layer is a semiconductor or a metal oxide. 3. The reverse conduction thyristor according to claim 1, characterized in that there is a separation region between the thyristor portion and the diode portion, and the connection path is provided in at least a portion of the separation region. 4. The reverse conduction thyristor according to claim 1, wherein the composite thyristor wafer is treated by a heavy metal diffusion method, a heat treatment method, or a radiation irradiation method to shorten the minority carrier life.