JPS60263464A - Reverse-conductivity gate turn-off thyristor device - Google Patents

Abstract

PURPOSE:To prevent erroneous ignition without reducing the area occupied by a GTO region and RCD region by a method wherein a drain region is provided in an isolating region for the expulsion of excessive holes. CONSTITUTION:A drain region 22 belongs to the same P type layer as an RCD anode layer 13' and is shaped when an n<+> layer 23 is formed by selective diffusion. The drain 22 region is set at the same potential as the anode layer 13' due to an anode electrode 19. To stop the p-n-p-n structure created at the lower portion of the n<+> type layer 23 from latchup, the surface of the n<+> type layer 23 is covered by an insulating film 21. It follows therefore that holes out of the excessive carriers forced out of an RCD region (b) into an isolating region (c) are collected by a cathode electrode 16 through the drain region 22, which effectively contributes to the prevention of erroneous ignition. The drain region 22 occupies an area not larger then 20% of the RCD region, and the current present in the drain region 22 is so small as to be less than 1% of the RCD current. This means that the drain region 22 virtually functions only to eliminate excessive holes.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a reverse conduction GTO device in which a gate turn-off thyristor (GTO) and a reverse conduction diode (RCD) are integrally formed on the same semiconductor wafer.

[Technical background of the invention and its problems]

A reverse conduction GTO device is one in which a GTO and an RCD that conducts a current in the opposite direction to the current flowing therein are integrally formed, and an example thereof is shown in FIG. GTO part a is p
+ type first emitter layer 11, n type first base layer 12,
P-type second base layer 13, n+ type second emitter layer 14
It consists of a four-layer structure. The second emitter layer 14 is divided into a plurality of parts. The RCD section includes an anode layer 13'' made of a p-type layer common to the second base layer 13 of the GTO section a, and a first
The base layer 12 is composed of an n-type layer 12-1 and an n+-type power sword layer 15, which are common to the base layer 12. 18 is an anode electrode provided commonly to the first emitter layer 11 and the cathode layer 15; 16 is a cathode electrode provided to each divided second emitter layer 14;
7 is the goo 1~electrode, and 19 is the anode electrode of the RCD. The anode electrode 19 and the cathode electrode 16 are electrically connected and placed at equal potential. GTO part a
There is a separate area 1C between the RCD section and the RCD section, where the second
A groove 20 is formed to substantially separate the base layer 13 and the anode layer 13''.
:GTO Goo 1~Electron lf! 17 and the cathode electrode 16, this causes RC[
) to prevent short-circuiting through the anode layer 13-.

FIG. 4 shows voltage and current waveforms when a positive voltage VA is applied to the GTO after a forward current ID flows through the RCD. G
When the diode current 1o as shown in the figure flows with TO in the OFF state, after 1 time t1, positive voltage is applied to GTO again, voltage VA recovers as shown by the solid line, and GT continues to operate.
It is required that O remains off. Koroga, RCD
When the rate of decrease in the diode current ID is large as indicated by the broken line, the GTO loses its blocking ability after time t1 and may cause erroneous ignition. This is because excess carriers in the RCD act as a trigger current for the GTO.

That is, the period during which the diode current In is flowing is 1 □
7L 1. :L RCD (7) A/-1-”1813
-#15. Electrons flow from the cathode layer 15 to the anode layer 13' to 115, respectively. And time a in Figure 4
When 'l j + is reached, the voltage between the anode and cathode of the GTO becomes opposite to that before time t1, and the anode becomes positive and the cathode becomes negative. At this time, excess electrons existing in the RCD section are discharged from the cathode layer 15 of the RCD, and excess holes are discharged from the anode layer 13'.

However, near the groove 20 formed in the separation region C and the GT
The excess carriers that have protruded to the O section a do not return until the RCD section, and the excess electrons pass through the first emitter layer 11 and are extracted from the anode electrode 18, prompting the injection of holes commensurate with the electrons. Passing through the second base layer 13 and passing through the gate electrode 17 near the isolation region C, the
In order to improve the dt withstand capability and the forward breakdown voltage, it is discharged to the cathode electrode 14 through a resistor RaK (not shown) connected between the gate and the cathode outside the device. This Rah
The voltage drop due to the current flowing through the second base layer 13
When the minimum gate trigger voltage corresponding to the built-in potential of the junction consisting of , corresponding electrons are injected from the second emitter layer 14 to the second base layer 13. Such an operation causes the GTO to fire incorrectly. This false ignition occurs as the rate of decrease dIr>/dt of the diode current ID increases.
This is likely to occur because the amount of excess carriers remaining in the separation region C, particularly holes, which have a lower mobility than electrons, increases.

In order to avoid such problems, in the past, the width of the isolation region C was made wide, so that the influence of excess carriers in the RCD section was reduced to
Measures are being taken to ensure that this does not extend to part a. However, increasing the width of the region C has the disadvantage that, assuming the same wafer area, the actual area of the 070 part and the RCD part decreases.

[Purpose of the invention]

In view of the above points, it is an object of the present invention to provide a reverse conduction GTO device that can reliably prevent erroneous ignition without reducing the substantial areas of the 070 section and the RCD section.

[Summary of the invention]

The present invention provides a drain region in the separation region between the 070 part and the RCD part to drain excess holes protruding from the RCD part to the cathode electrode without passing through the base layer of the 070 part. Features. This train region is formed of the same p-type layer as the p-type anode layer of the RCD section, and is kept at the same potential as the p-type anode layer. In addition, this drain region should be provided as close to the 070 part as possible in order to reduce the protrusion of holes to the 070 part, and its area should be determined by considering the ratio to the area of the RCD and the distance from the RCD when the RCD is energized. It is necessary to select such that the current flowing through this portion is sufficiently small.

(Effects of the Invention) According to the present invention, by providing the drain region for discharging excess holes in the isolation region, GTO can be reliably maintained even when the reduction rate diD/dt of the RCD diode current is large.
6- It is possible to prevent erroneous ignition. Also, as a result of providing the drain region, in order to prevent erroneous firing at the dIo/dt required by the circuit,
The width of the region can be made smaller than before, and if the wafer area is the same, the actual area of the GTO section and the RCD section can be increased.

[Embodiments of the invention]

FIG. 1 shows a reverse conduction GTO device according to an embodiment of the present invention. Parts corresponding to those in FIG. 3 are given the same reference numerals as in FIG. 3. The difference between this embodiment and the conventional one is that
The point is that a drain region 22 is provided within the IC. The drain region 22 is similar to the anode layer 13' of the RCD.
It consists of a type layer and is formed by selectively diffusing the n++ layer 23. The drain region 22 is the anode electrode 19
It is set to have the same potential as the anode layer 13'.

Since the underside of the n++ layer 23 has a pnpn structure, the surface of the n++ layer 23 is covered with an insulating film 21 to prevent latch-up in this portion.

’ ash□, □, a. . . 1o, 1st grade.

The layer 11 has a surface impurity concentration of 1.0×1018/CI
l+3. The first base layer 12 has a diffusion depth of 50 μm and an impurity concentration of 6.5×10 13 /cm 3 . The thickness of the second base layer 13 is 250 μm, and the surface impurity concentration lXl018
10n3. The second emitter layer 14 is formed by diffusion to have a diffusion depth of 50 μm, and has an impurity concentration of 1019/cII.
I3 or more, the diffusion depth is 10tlTrL. The cathode layer 15 in the RCD section has a surface impurity concentration of 2. OXl 01! I/arr3. Diffusion depth 70
μm, the anode 1113' is formed by diffusion at the same time as the second base layer 13 of the GTO section, and the drain region 22
The n++ layer 23 for increasing 1q is formed by diffusion at the same time as the second emitter layer 14 of the GTO section.

In this embodiment, the width of the isolation region C is d=500μ, and the width of the n++ layer 23 is de-200μ.

According to this embodiment, holes among the excess carriers protruding from the RCD 811b into the separation region C are discharged to the cathode electrode 16 via the drain region 22, and erroneous firing is effectively prevented. The area of the train region 22 is 2 of the RCD area.
0% or less, and at this time, the current flowing through the drain region 22 is a small value less than 1% of the RCD current, and the train region 22 substantially functions only to discharge excess carriers. In order to have the same level of false ignition prevention function as this embodiment in a conventional structure without a drain region, the width of the isolation region C must be 1.211I#I, and in this embodiment, the isolation region The width of C is 1/1 compared to the conventional structure.
2 or less will suffice. Therefore, when a wafer of the same size as the conventional one is used, the substantial area of the GTO section and the RCD section can be increased.

FIG. 2 shows the structure of another embodiment of the present invention. The difference from the embodiment shown in FIG. 1 is that a groove 24 is formed instead of the n++ layer 23 to form the drain region 22. 25 is a train electrode, which is connected to the cathode electrode 16. This also provides the same effect as the embodiment shown in FIG.

The present invention can be further modified in various ways.

9- For example, if combined with the technique of doping the isolation region with a lifetime killer, a reverse conduction GTO that operates safely up to a larger dTo/dt can be obtained. Also, the groove 20 in the separation region
Instead, an n+ type scattering layer may be used, and an insulating film may be used for the n++ layer 23 and groove 24 for forming the groove 20 or the drain region 22.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of a reverse conducting GTO according to an embodiment of the present invention, FIG. 2 is a diagram showing the structure of a reverse conducting GTO according to another embodiment, and FIG. 3 is a diagram showing the structure of a conventional reverse conducting GTO. The figure shown in FIG. 4 is a diagram for explaining the operation of the reverse conduction GTO. 11... First emitter layer, 12... First base layer,
13... Second base layer, 14... Second emitter layer,
15... ROD cathode layer, 13'... RCD anode layer, 16... cathode electrode, 17... gate electrode, 18... anode electrode, 19... RCD anode electrode, 20... Groove, 21... Insulating film, 22...
Drain region, 23... n+ type layer, 24... groove, 2
5... Train electrode, 10- a... GTO section, b... RCD section, C... Separation region. -11-

Claims (1)

[Claims] In a reverse-conducting gate turn-off thyristor device in which a gate turn-off thyristor and a reverse-conducting diode are integrally formed on the same semiconductor wafer, the gate turn-off thyristor and the reverse-conducting diode are kept at the same potential in the separation region of the anode layer of the reverse-conducting diode. A reverse conduction gate turn-off thyristor device comprising a drain region for discharging excess holes of a reverse conduction diode to a cathode electrode without passing through the base layer of the gate turn-off thyristor.