JPH0936347A - Doubled-sided semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent concentration of a surge current, and improve surge resistance, by arranging short-circuit holes in the outer peripheral part of an exclusive region to an emitter which holes reach the common region of a base and an emitter and are filled with a first conductivity type layer. SOLUTION: In order to increase surge resistance, injection efficiency into the outer peripheral part of an exclusive region to an emitter where current concentration is liable to be generated, especially, into a common region of an base and an emitter in the part stretching from the part of the side close to the outer peripheral part of a substrate to the part just under the exclusive region to the emitter is lowered by emitter short-circuit structure. For example, short-circuit holes 5 are arranged in the part on the side close to the chip outer periphery of the outer peripheral part of N emitters 31, 32. The short-circuit holes 5 penetrate the emitter, reach a P<+> layer 21 or 22 under the emitter, and are filled with a P<+> layer 23. When a surge voltage is applied, a circuit is turned on from the outer periphery of a two-terminal thyristor chip. The ON-current is made to escape to an electrode through the short-circuit holes 5. Thereby the surge current resistance can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-sided semiconductor device having a bidirectional symmetrical characteristic of a current flowing between both main surfaces of a semiconductor substrate.

[0002]

2. Description of the Related Art A self-ignition double-sided semiconductor device having bidirectional symmetry has a symmetrical sectional structure. FIG. 2 shows a structure of a conventional bidirectional two-terminal thyristor, in which the n ⁺ layer 3 is provided on the surface layers of the p ⁺ layers 21 and 22 sandwiching the n ⁻ layer 1.
1 and 32 are formed in line symmetry. Although not shown in the figure, on both main surfaces, the electrodes commonly contacting the shaded surface of the n ⁺ layer 31 and the exposed surface of the p ⁺ layer 21, and the shaded surface of the n ⁺ layer 32 are shown. An electrode is provided in common contact with the exposed surface of the p ⁺ layer 22.

This semiconductor device has a p-emitter layer 21, n
The pnpn structure thyristor of the base layer 1, the p base layer 22 and the n emitter layer 32 and the pnpn structure thyristor of the p emitter layer 22, the n base layer 1, the p base layer 21 and the n emitter layer 31 are provided in antiparallel. Therefore, by applying a voltage that is equal to or higher than the breakover voltage or a voltage that has a steep rise above the critical off-voltage rise rate, bidirectional
It is possible to shift from the OFF state to the ON state.

[0004]

The holding current and the surge current withstanding capability of the semiconductor device as shown in FIG. 2 have a trade-off relationship. That is, for example, if the impurity concentration Cnp of the p base layer in contact with the interface with the n emitter layer is increased, the holding current I _H is increased but the surge resistance is significantly reduced. The surge current withstand level decreases when the surge current is concentrated. A self-reset type two-terminal thyristor is required to have both high holding current and surge withstand capability.

[0005] Japanese Patent Application No. Hei.
No. 155,091 discloses a double-sided semiconductor device in which the concentration of surge current is relaxed and the surge withstand current is increased at the same holding current, as shown in FIG. 41, 4
Comb shape with 2 and comb teeth 41, 4 on both sides
2 is point symmetric with respect to the center point of the n ⁻ layer 1,
And as shown in FIG. 4, one of the comb teeth 41, 4
2 is arranged so as to vertically overlap with the gap between the teeth 41 and 42 of the other comb.

It is an object of the present invention to provide a double-sided semiconductor device having such a tooth-shaped emitter-dedicated region and having an improved trade-off relationship between surge withstand current and holding current. .

[0007]

In order to achieve the above object, the present invention is formed on both main surface sides of a semiconductor substrate in a base / emitter combined area of the first conductivity type and a surface layer of the area. The second-conductivity-type emitter-dedicated region is exposed, and the shapes of the base / emitter dual-use region and the emitter-dedicated region on both sides are point-symmetric with respect to the center point of the substrate, and the shape of the emitter-dedicated region is comb-shaped. In the double-sided semiconductor device, the teeth of the emitter-only area on one side face the gaps of the teeth of the emitter-only area on the other side in the direction perpendicular to the main surface of the substrate.
It is assumed that a short-circuit hole reaching the combined base / emitter region and filled with the first conductivity type layer is provided on the outer periphery of the emitter-dedicated region. It is also effective that the peripheral edge of the tooth in the emitter-only area on the one surface side and the peripheral edge of the tooth in the emitter-specific area on the other surface side overlap with the main surface of the substrate in the vertical direction by a width of 10% or less of the width of the tooth portion. is there. It is preferable that the short-circuit hole is provided at an extension of the center line of the comb-shaped tooth. It is also good that the short-circuit hole is provided only in a portion of the outer peripheral portion of the emitter-dedicated area near the outer periphery of the semiconductor substrate. The impurity concentration of the dual-purpose base / emitter region is increased only in the portion of the outer peripheral portion of the emitter-dedicated region that is close to the outer peripheral portion of the semiconductor substrate.・ It is good to reach the area dedicated to the emitter.
No. It is effective that the depth of the emitter-dedicated region is deeper than that of the outer periphery where the short-circuit hole is provided in the inner periphery of the region. The depth of the emitter-dedicated region becomes deeper from the outer periphery toward the inner periphery. It was good that it was done.

[0008]

As described in the above-mentioned specification, the comb structure serves to increase the current capacity of the emitter regions having the same occupation area by increasing the peripheral length, as is done in the transistor. Therefore, even with respect to the surge current, the concentrated current becomes small, and it is possible to mitigate the reduction in withstand amount due to the current concentration. In a double-sided semiconductor device, by preventing the comb-shaped structures formed on both sides from overlapping,
Both layer structures formed with point symmetry can be utilized. However, the circumference of the tooth part is 10
%, The effective layer structure area is less reduced, while the peripheral length of the emitter region is somewhat increased, which may be effective in improving the surge resistance.

In order to further increase the surge withstand capability, a base / emitter dual-use region of the outer peripheral portion of the emitter-dedicated region where current concentration is likely to occur, particularly the portion extending from the portion near the outer peripheral portion of the substrate to directly below the emitter-dedicated region. The injection efficiency into the emitter is reduced by the shorted emitter structure. Providing a short-circuit hole for emitter short-circuiting on the deepest center line of the tooth part of the emitter-only area of the comb structure has a strong effect on lowering the injection efficiency.
Meru. Such an emitter short-circuit structure is used when increasing the impurity concentration in the portion of the emitter-dedicated area close to the outer periphery of the substrate described in the above specification, or making the inner peripheral portion of the emitter-dedicated area deeper than the outer peripheral portion. When used together, the effect of improving surge withstand capability is further enhanced.

[0010]

Embodiments of the present invention will be described below with reference to the drawings in which the same parts as those in FIGS.
In a two-terminal thyristor according to one embodiment of the present invention shown in FIG. 1 (a) of a plan view similar to FIG. 4, in the chip outer periphery of the n emitters 31 and 32,
The short-circuit hole 5 is provided in the portion on the side close to. FIG.
As shown in FIG. 1B, which is a cross-sectional view taken along the line AA of FIG. 1A, the short-circuit hole 5 penetrates the emitter, and the p
^{The +} layer 21 or 22 is reached and filled with the p ⁺ layer 23. When a surge voltage is applied, it turns on from the outer periphery of the two-terminal thyristor chip. By releasing this on-current to the electrode through the short-circuit hole 5, the surge current withstand capability can be improved.
Therefore, the short-circuit hole 5 is provided in the outer peripheral portion of the n emitters 31 and 32 near the outer periphery of the chip. The position of the short contact hole 5 is
It is desirable to be located closer to the outer circumference than half the width of the emitter strip pattern from the edge of the emitter.

In another embodiment shown in FIG. 5, among the short-circuit holes 5 in the embodiment of FIG. 1, those on the side closer to the tip outer circumference of the comb teeth 41, 42 are omitted, but this is also sufficiently effective. can get. In the embodiment shown in FIGS. 6A and 6B, the number of short-circuit holes 5 in the embodiment of FIG. 1 is reduced, and what is formed on the outer peripheral portion of the base of the comb tooth is the tooth portion of each comb. 41 or 42 on the center line with the longest depth. Instead, the diameter d of the short circuit hole 5 was set to 1/3 of the width w of the tooth portions 41 and 42 of the comb.
In this example, w = 300 μm and d = 100.
μm. The distance between the short-circuit holes 5 formed on the outer peripheral portions of the outermost comb teeth 41 and 42 was about 2 w, that is, about 600 μm.

In the embodiment of the present invention as set forth in claim 5 shown in FIG. 7, a p ⁺⁺ layer 24 is formed immediately below the outer periphery of the tooth portions 41, 42 of the n ⁺ emitter layer near the outer periphery of the chip. The injection efficiency from the n-emitter layer to the p-base layer is reduced to prevent the current from concentrating in the outer peripheral portion, and the short-circuit hole 5 penetrates the n ⁺ layers 31 and 32 inside thereof.

In the embodiment of the present invention according to claims 6 and 7 shown in FIG. 8, the depth of the n ⁺ emitter layer is the central portion 43 as shown in the cross section of the comb tooth portion 41 of the n ⁺ layer in the figure. At the outermost portion, the next deepest portion at the outermost portion 44, and the shallowest portion at the outermost portion 45 to prevent current collection to the outer peripheral portion. It is high. Although not shown, the same applies to the comb teeth 42 on the back side.

In the embodiment of the present invention as set forth in claim 1 shown in FIG. 9, the short-circuit holes 5 are formed not only in the outer peripheral portions near the outer peripheral portions of the comb tooth portions 41, 42 of the n ⁺ emitter layer but also in all the outer peripheral portions. The surge resistance is further increased by opening the. In the above embodiment, the emitter-dedicated region is n-type, but p-type
It is clear that a two-way two-terminal thyristor in the case of the form can be implemented as well.

[0015]

According to the present invention, in addition to adopting the comb-shaped structure in the emitter-dedicated region and also using the emitter short-circuit structure in the outer periphery of the emitter-dedicated region, the concentration of surge current is prevented and the surge withstand capability is improved. Therefore, the trade-off characteristics of surge withstanding characteristics and holding current characteristics are improved. As a result, a double-sided semiconductor device with a large holding current and a large surge resistance can be obtained, and the die size of the double-sided semiconductor device can be reduced.
Came. Immediately below the outer periphery of the emitter-dedicated region where current concentration is likely to occur, increase the impurity concentration in the base / emitter region to reduce the injection efficiency, or increase the current amplification factor of the transistor structure to make the emitter-dedicated region deeper in the inner periphery. By doing so, it is possible to use it together with the increase in the outer peripheral portion, so that the surge withstand capability can be further improved.

[Brief description of drawings]

1A and 1B show a bidirectional two-terminal thyristor according to an embodiment of the present invention, FIG. 1A is a plan view of a semiconductor substrate, and FIG. 1B is a sectional view taken along line AA of FIG.

FIG. 2 is a cutaway perspective view of a conventional bidirectional two-terminal thyristor.

FIG. 3 is a cut-away perspective view of a bidirectional two-terminal thyristor having a comb-shaped emitter.

4 is a plan view of a semiconductor substrate of the thyristor of FIG.

FIG. 5 is a plan view of a bidirectional two-terminal thyristor semiconductor substrate according to a different embodiment of the present invention.

FIG. 6 shows a bidirectional two-terminal thyristor according to another embodiment of the present invention, in which (a) is a plan view of a semiconductor substrate and (b) is a sectional view taken along line BB of (a).

FIG. 7 is a plan view of a bidirectional two-terminal thyristor semiconductor substrate according to another embodiment of the present invention.

FIG. 8 is a sectional view of a bidirectional two-terminal thyristor semiconductor substrate according to another embodiment of the present invention.

FIG. 9 is a plan view of a bidirectional two-terminal thyristor semiconductor substrate according to another embodiment of the present invention.

[Explanation of symbols]

1 n ^- layer 21, 22, 23 p ⁺ layer (base-emitter combined region) 24 p ⁺⁺ layer 31 and 32 n ⁺ layer (emitter-only area) 41 comb teeth 5 shunt hole of

Claims (7)

[Claims] 1. A base / emitter dual-use region of the first conductivity type and a second conductivity type emitter-dedicated region formed in a surface layer of the region are exposed on both main surface sides of a semiconductor substrate,
The shapes of the base / emitter combined area and the emitter-only area on both sides are point-symmetric with respect to the center point of the substrate.
In a double-sided semiconductor device where the emitter-dedicated region has a comb shape, and the teeth of the emitter-dedicated region on one side face the gap between the teeth of the emitter-dedicated region on the other side in the direction perpendicular to the main surface of the substrate. A short-circuit hole that reaches the combined base / emitter region and is filled with the first conductivity type layer on the outer periphery of the emitter-dedicated region.
A double-sided semiconductor device comprising: 2. A peripheral edge of a tooth of the emitter-dedicated area on one surface side and a peripheral edge of the tooth of an emitter-dedicated area on the other surface side overlap each other in a direction perpendicular to the main surface of the substrate by a width of 10% or less of the width of the tooth portion. The double-sided semiconductor device according to claim 1. 3. The double-sided semiconductor device according to claim 1, wherein the short-circuit hole is provided in an extension of the center line of the teeth of the comb-shaped base. 4. A double-sided semiconductor device according to claim 1, wherein the short-circuit hole is provided only in a portion of the outer peripheral portion of the emitter-dedicated region near the outer periphery of the semiconductor substrate. 5. The impurity concentration of the dual-purpose base / emitter region is increased only in a portion of the outer peripheral portion of the emitter-dedicated region which is close to a portion closer to the outer periphery of the semiconductor substrate,
5. The double-sided semiconductor device according to claim 1, wherein the short-circuit hole reaches the combined base / emitter region inside the region having a high impurity concentration. 6. A double-sided semiconductor device according to claim 1, wherein the depth of the region dedicated to the emitter is made deeper than the outer peripheral portion where the short-circuit hole is provided in the inner peripheral portion of the region. 7. The double-sided semiconductor device according to claim 6, wherein the depth of the emitter-dedicated region is increased from the outer peripheral portion toward the inner peripheral portion.