JPS609667B2 - Semiconductor controlled rectifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor-controlled rectifier device, which aims to be capable of ignition with a small control current and to reduce dv/d.
The objective is to improve the t tolerance.

Generally, a semiconductor controlled rectifier (hereinafter referred to as a thyristor) which is ignited by a control electrode has a semiconductor substrate having a pnpn four-layer junction structure, and two thyristors provided on the p-layer and n-layer on both sides of the semiconductor substrate. The control electrode is connected to either the intermediate p layer or the n layer. For example, when a high dv/dt is applied to the structure shown in Figure 1, the displacement current is P2
It flows from the layer to the cathode electrode 1 as shown by the arrow, but it also flows to the cathode electrode 1 through the p2 layer below the surrounding & layer. The current passing through the p2 layer under the surrounding mountain layer is the total current flowing through the exposed p2 layer around the − layer, so the p2 shown in Figure 1B is
The lateral voltage drop V^B across the layer becomes high and can be of sufficient value to fire the thyristor. Therefore, the dv/dt tolerance is low. On the other hand, various control electrode structures have been proposed to improve the initial ignition characteristics. An example is shown in FIG. The thyristor has a so-called pilot gate structure in which an emitter layer 13 of an auxiliary thyristor layer is provided between a gate electrode 11 and an emitter layer 12, and the auxiliary thyristor electrode 14 is p
It is provided on the base layer 15 so as to face the emitter layer 12 .

In this one, the emitter electrode 16 and the auxiliary thyristor electrode 1
The initial ignition area can be improved by increasing the distance between the opposing portions of No. 4. That is, the emitter electrode 16 facing the auxiliary thyristor electrode is formed so that the surface of the end of the emitter layer 12 is exposed, and the gate current flowing from the auxiliary thyristor electrode flows into the pn of the end of the emitter layer.
The gate current flows into the junction and becomes effective. The voltage drop caused by the displacement current in such a thyristor is seen in FIG.

3A shows a portion of the gate current near the end of the emitter layer and facing the end of the emitter layer, and FIG. 3B shows a sectional view taken along line BB in FIG. 3A. Assuming that the displacement current generated outside the emitter layer 12 flows into the short-circuit emitter hole 201 closest to the end of the emitter layer as shown by the arrow, the third
The voltage drop between a and b in Figure B is expressed by the following equation. In other words, assuming that the short-circuit emitters near the periphery are arranged regularly, and calculating the voltage drop due to the displacement current in the unit part, we can calculate the voltage drop due to the displacement current in the unit part. Resistance J is the displacement current density S = 3xlo-2 (ground) *S is the area of the surrounding p layer where the displacement current occurs J = C = D - density = 1.

-lab In the case of a normal silicate layer, the value of the p layer below the n+ layer is 1 p to 1 p (Q), and since C is 800 PE/(at V et 0), J: 8× 1o-・0 group (A
), the peripheral dimensions are at least lo = 3 skin, lab = 1
Since the side is necessary, -・-Vab=(1pi~sail×(8
×1o-10〉X(3×・o-2〉=2-4(・o-
In order to prevent the pn junction from injecting charge due to this voltage drop, it is necessary that the voltage is below the threshold value of the pn junction.

As is generally known, the threshold value of a pn junction is 0.
．． Since it is 5V, 2-4 (lo-3 to 10-9) group = o
-5 Therefore group: 2-o8×・pi~2-o8×1 and <V′Sec>=
(200~20〉(VruS〉Hiroshi Tolerance 2o~2ooV/
〃S' distribution is the ratio.

The object of the present invention is to provide a thyristor with further improved group withstand capability, and to achieve the object by improving the short-circuit structure at the end of the emitter layer facing the gate electrode.

The present invention will be explained below with reference to the drawings.

FIG. 4A shows a top view of a part of the thyristor of the present invention, and FIG. 4B shows a sectional view taken along the line BB in FIG. 4A. As is clear from FIG. 4, the thyristor of the present invention has the following structure. That is, the first region 21 whose conductivity type is n,
The second and third regions 22 and 23, which are adjacent to both main surfaces of the first region and have a p conductivity type, the third region (base layer).
A fourth region (emitter layer) 24 of conductivity type n which is partially exposed on the surface and formed within this region, and a first electrode (anode electrode) provided on the surfaces of the second and fourth regions, respectively. 25, a second electrode (canodic electrode) 26, and the third electrode
A third electrode (auxiliary gate electrode) 27 is provided on the surface of the region to surround the second electrode and spaced apart from the second electrode, and a third electrode (auxiliary gate electrode) 27 is provided on the surface of the third region on the opposite side of the fourth region to the third electrode 27. A fifth region 29 of n conductivity type is formed in a third region under the gate electrode 28 and the third electrode 27 and is partially exposed on the surface and spaced apart between the gate electrode and the fourth region. Equipped with. In the syringe with the above structure, the fourth region (
The end surface of the emitter layer 24 on the side facing the gate electrode is formed in an uneven shape as shown in FIG. The resulting cathode electrode covers the recessed portion of the emitter layer, and the p base layer and n emitter layer are short-circuited.

Therefore, unlike the conventional case, the displacement current flows into the short-circuited portion at the end of the emitter layer.

Looking at the voltage drop between the gate and cathode due to the displacement current at this time, when calculated for the unit part in the same way as above, VCd:FCd. J. s・Yutaka=pCd le, Cd where p is the average resistance of the peripheral unit part of the p base layer, and in a normal thyristor, it is ±=7xlo-2~1.7x
It is distributed in the range of lo-1, and P
※Ru.

．．・．． So; 6-15 (0) Also J=C group, 1.

-ICd: 3 x 10-2 where lo is the distance between the end of the pellet and the end of the emitter layer, and lcd is the distance between the end of the emitter layer and the shorted emitter part closest to the emitter layer weave.

Therefore, as in the calculation formula above, since the pn junction threshold value is 0.5V, o-5=
VCd=(6~15)X(8×10-10)X(3-
2) Group X--Festival=6-94×・Pi~2-78×1■'S
ec = 6-94 x 1 pi ~ 2-78 x 1 book S.

In other words, it is distributed between the group tolerance side ooV Lusa and 25ooV Le S side.

The displacement current around the element that causes such an edge drop is equally divided into each short-circuited portion, and most of it flows from the base region toward the cathode electrode.

Therefore, the present invention is significantly superior in terms of performance. Furthermore, in the thyristor having the above structure, if the end face of the n-conductivity type fifth region on the gate side is formed into an uneven shape, the group withstand capability can be independently improved.

Unlike the structure described above, thyristors with various structures, such as the one shown in FIG. It goes without saying that it is implied that if a structure having an uneven shape is applied, the group resistance will be improved.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional semiconductor-controlled rectifier, Fig. 2 is a sectional view of the same, and Fig. 3 is a plan view of a part of the conventional semiconductor-controlled rectifier, and B is a B-B of A. 4 is a plan view of a part of one embodiment of the present invention, B is a sectional view taken along line B-B of A, and FIG. FIG. 2 is a plan view showing a part of the embodiment. 21......n-type first region, 22...
・P-type second region, 23...p-type third region, 24
. . . N-type fourth region, 25 . . . first electrode, 26 . . . second electrode, 27 . . . third electrode, 28. ...Gate electrode, 29...
...Fifth area. 1st ball, 2nd figure, 3rd book, 4th figure, 5th figure

Claims (1)

[Claims] 1 A first region of a first conductivity type, second and third regions of a second conductivity type formed adjacent to both main surfaces of the first region, and a portion of the surface of the third region. a fourth region of the first conductivity type exposed and formed in the third region; first and second electrodes provided on the surfaces of the second and fourth regions, respectively; and the third region. a control electrode provided on the surface of the electrode separated from the second electrode; a fifth region of the first conductivity type formed in the third region on the control electrode side and separated from the fourth region; In a semiconductor controlled rectifier device comprising: a third electrode provided on surfaces of the third and fifth regions to be spaced apart from each other between the second electrode and the control electrode and substantially surrounding the fourth region; A semiconductor-controlled rectifier device, characterized in that the end face of the fourth region on the third electrode side is formed in an uneven shape, and the third region and the fourth region are short-circuited at the plurality of concave portions.