JPH05145063A - Gate turn-off thyristor - Google Patents

Abstract

PURPOSE:To uniformly turn ON an entire GTO thyristor, to eliminate a current concentration to a specific element and to prevent a damage of the element by surrounding a plurality of unit gate turn-off (GTO) thyristors discontinuously with a plurality of small circular unit emitter short-circuiting layers. CONSTITUTION:Unit GTO thyristors are radially formed in a ring state on a semiconductor pellet 1, and a discontinuous and small circular dotlike emitter short-circuiting layer 22 is so disposed outside a projected part of a second emitter layer 11 of a cathode side as to surround the projected part. The GTO thyristor is forwardly biased between its gate and its cathode in the operation, and a hole current flows from a gate electrode 4 to a cathode electrode 3. Then, electrons are emitted from the layer 11 correspondingly, and an electron current Ie flows to an anode electrode 6. Thereafter, a hole current Ih flows from a first emitter layer 7 of an anode side to the electrode 3. This is repeated to turn ON the thyristor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gate turn-off thyristor (hereinafter abbreviated as GTO thyristor).

[0002]

2. Description of the Related Art Currently, there are four high voltage GTO thyristors.
A device of 500 to 6000 V is manufactured, and for example,
In the 4500V element, the depletion layer is about 600μ on the N base side.
m also extends. Therefore, considering the reliability of the element, N
A base width of 800 to 900 μm is also required. As the N base width increases, steady loss increases, which is a big problem for large current and high speed operation. In order to improve these problems, a PIN structure in which an N-type buffer layer having a high impurity concentration is added to the N base layer is known. A conventional GTO thyristor having this structure is shown in FIGS. 4 is a top view of a GTO thyristor obtained by dividing a semiconductor pellet into four parts, FIG. 5 is a sectional view taken along line XX of FIG. 4, and FIG. 6 is a unit G.
It is an enlarged view of a TO thyristor, (A) is the top view seen from the cathode side, (B) is the sectional view.

In these figures, the semiconductor pellet 1
In addition, unit GTO thyristors are formed radially and in a ring shape, and 2 indicates its cathode emitter segment. 3 is a cathode electrode provided on the cathode emitter segment 2 (see FIG. 5), 4 is a gate electrode provided on the gate region of the dug portion, and 5 is a gate electrode.
An insulating film for insulating between the cathodes, 6 is an anode electrode provided on the other main surface, 7 is a first emitter layer, 8 is an N-type buffer layer, 9 is a first base layer, and 10 is a second base. Layer, 11 is the second emitter layer, 12 is the second emitter layer 11
Is a short-circuited emitter layer formed on the portion projected to the anode side, and 13 is a short-circuit resistance between the N-type buffer layer 8 and the anode electrode 6.

[0004]

By the way, the conventional GTO thyristor having the above structure has the N-type buffer layer 8
Is formed of a high-concentration impurity layer and has a low resistance, the short-circuit resistance 13 becomes too small, and the GTO
The gate trigger current when turning on the thyristor becomes large. Therefore, unless the gate trigger current is increased, a voltage drop due to the short-circuit resistor 13 for turning on cannot be generated, and in some cases, the GTO thyristor cannot be turned on, or only some unit GTO thyristors cannot be turned on. There was a problem to be solved that the unit GTO thyristor may be turned on and destroyed.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is provided with a G having an emitter short-circuit layer and a buffer structure capable of making the trigger gate current smaller than in the prior art.
The purpose is to provide a TO thyristor.

[0006]

A GTO thyristor of the present invention is a gate turn-off thyristor having a PNIPN structure and a plurality of unit gate turn-off thyristors having an emitter shorting layer arranged in parallel in a semiconductor substrate. The emitter shorting layer is characterized in that the periphery of the plurality of unit gate turn-off thyristors is discontinuous and surrounded by a plurality of small circular unit emitter shorting layers.

[0007]

In the GTO thyristor of the present invention, the periphery of the unit GTO thyristor is surrounded by the so-called dot-shaped unit emitter short-circuit layer. Radial flow directly below. Therefore, the short-circuit resistance between the N-type buffer layer and the anode electrode increases as the path of the electron current becomes longer. Therefore, even if the trigger gate current is made smaller than in the conventional case, the hole current from the first emitter layer is increased. Becomes larger and it becomes easier to turn on.

[0008]

Embodiments of the present invention will be described below in detail with reference to FIGS. First, the structure of the cathode side in the GTO thyristor of the present invention is the same as the conventional one,
A unit GTO thyristor is formed in a radial shape and a ring shape on the semiconductor pellet 1, and 2 indicates its cathode emitter segment (see FIGS. 1 and 2). Also, FIG.
The reference numerals of the respective layers are also the same as those of FIG. 5 showing the conventional structure. The feature of the present invention lies in the arrangement of the emitter shorting layer on the anode side. That is, in the portion of the first emitter layer 7 where the second emitter layer 11 on the cathode side is projected on the anode side,
Without providing an emitter short-circuit layer, as shown in FIG. 1 or FIG. 2A, a so-called dot-shaped emitter short circuit, which is discontinuous and small, is formed outside the projected portion of the second emitter layer 11. The layer 22 is arranged so as to surround the projected portion. When the number of the dot-shaped emitter short-circuit layers 22 is gradually increased, the projected portion is completely surrounded by the N-type high-concentration impurity layer. With this,
The trigger gate current increases, and a unit GTO thyristor that does not turn on like the conventional one appears. Therefore, in the present invention, it is an important constituent element that the projection portion is not completely surrounded but is discontinuously surrounded.

Next, the operation of the GTO thyristor will be described with reference to FIG. In the figure, first, GT
Forward turn on the gate and cathode to turn on the O thyristor. Then, a hole current flows from the gate electrode 4 toward the cathode electrode 3. Next, correspondingly, electrons are emitted from the second emitter layer 11, and an electron current Ie flows toward the anode electrode 6 in the direction of the arrow. Then, correspondingly, the hole current Ih flows from the first emitter layer 7 on the anode side toward the cathode electrode 3 in the direction of the arrow. By repeating this, the GTO thyristor is turned on.

By the way, in the structure of the conventional GTO thyristor, since the emitter short-circuit layer 12 exists in the portion where the second emitter layer 11 is projected to the anode side, the electron current Ie is short-circuited in the projection portion. It flows through the layer 12 to the anode electrode 6 and therefore, the hole current I
h was not effectively released, and the trigger gate current was large as described above. In the structure of the present invention, since the emitter short-circuit layer 22 is arranged in a dot shape outside the projected portion of the second emitter layer 11 on the cathode side, the electron current Ie is emitted from the second emitter layer 11 as in the conventional case. It does not flow directly below, but flows diagonally below. For this reason, the short-circuit resistance 23 between the N-type buffer layer 8 and the anode electrode 6 is connected to the electron current I.
The length of the passage of e can be increased as much as possible. Therefore, even if the trigger gate current is made smaller than in the conventional case, the hole current Ih from the first emitter layer 7 becomes large and it becomes easy to turn on.

Next, FIG. 2 shows a specific structural example of the emitter shorting layer 22. Second emitter layer 1 in which cathode emitter segment 2 has width = 300 μm and length = 2500 μm
Around the projected portion when 1 is projected on the anode side,
Twelve emitter short-circuit layers 22 having a diameter of 40 μmφ were arranged. In the above case, the trigger gate current per cathode emitter segment 2 required 7 mA in the conventional case, but was improved to 1.5 mA in the present invention.

[0012]

As described above, according to the present invention, the periphery of the plurality of unit GTO thyristors is discontinuous and surrounded by the plurality of small circular unit emitter short-circuit layers.
The trigger gate current is small, the entire unit GTO thyristor can be turned on uniformly, there is no current concentration on a specific object, and there is an excellent effect that element breakdown does not occur.

[Brief description of drawings]

FIG. 1 is a top view of a GTO thyristor of the present invention in which a semiconductor pellet is divided into four parts, as viewed from the cathode side.

FIG. 2 is a unit GTO in the GTO thyristor of the present invention.
It is an enlarged view of a thyristor, (A) is the top view,
(B) is a sectional view taken along the line YY.

FIG. 3 is a sectional view showing a structure of a GTO thyristor of the present invention.

FIG. 4 is a top view of a conventional GTO thyristor in which a semiconductor pellet is divided into four, viewed from the cathode side.

5 is a cross-sectional view taken along line XX in FIG. 4 showing the structure of a conventional GTO thyristor.

6A and 6B are enlarged views of a unit GTO thyristor in a conventional GTO thyristor, FIG. 6A being a top view thereof, and FIG.
Is a sectional view taken along the line ZZ.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor pellet 2 Cathode emitter segment 3 Cathode electrode 4 Gate electrode 5 Insulating film 6 Anode electrode 7 First emitter layer 8 N-type buffer layer 9 First base layer 10 Second base layer 11 Second emitter layer 22 Emitter short-circuit layer 23 Short circuit resistance

Claims (1)

[Claims] 1. A gate turn-off thyristor having a PNIPN structure and having a plurality of unit gate turn-off thyristors provided in parallel in a semiconductor substrate, wherein the emitter short-circuit layer has a plurality of unit gate turn-offs. A gate turn-off thyristor characterized in that the thyristor is surrounded by a plurality of small circular unit emitter short-circuit layers around the thyristor.