JPH03225961A - Semiconductor element - Google Patents

Abstract

PURPOSE:To sharply enhance the area utilization rate of an element by a method wherein a GTO thyristor part and a diode part are provided with a PIN structure, their boundary is formed under specific conditions, a groove formed as a second processing part is dug and the groove is filled with a surface-protective material. CONSTITUTION:In order to form an isolation part 28, one groove having bevel angles theta1, theta2 is dug, by using a sand blast or the like, in the boundary part of a diode part 2 and a GTO thyristor part 1 ; the depth of the groove is formed until the groove reaches an anode electrode 4 or its neighborhood; the groove part is filled with a surface-protective material 9. The groove in the isolation part 28 is provided with a first processing part A and a second processing part B from the side of a cathode electrode to the side of the anode electrode 4 of an element. It is provided with a part which occupies 4/5 or higher from the side of a P-base layer PB out of the side face of an N-base layer NB<-> and with the same inclination with reference to a junction face of the PB and the NB<->. The angles theta1, theta2 formed by the inclination of the first processing part A and the junction face of the PB and the NB<-> are respectively 90 deg.+ or -15 deg.. Angles theta3, theta4 formed by the inclination of the second processing part B and junction face of the NB<-> and an N are 60 deg.+ or -20 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a semiconductor device, and more particularly to a reverse conduction type gate turn-off (GTO) thyristor having an integrated structure of a gate turn-off thyristor and a diode in antiparallel.

B1 Summary of the Invention The present invention provides a semiconductor device in which a GTO thyristor part and a diode part are formed on the same wafer, in which the GTO thyristor part and the diode part are formed in a PIN structure, and the GTO thyristor part and the diode part are formed in a PIN structure.
By digging a single groove of a predetermined shape at the boundary between the thyristor part and the diode part to form a separation part, the withstand voltage is improved, the area utilization rate of the element is increased, and the processing shape is simplified and the processing time is reduced. This is intended to shorten the time period.

C1 Conventional technology gate turn-off thyristor (hereinafter abbreviated as GTO):
It is widely used as a self-extinguishing semiconductor device in power converters and the like. In this application, diodes are often connected in antiparallel like a voltage source inverter. In order to reduce the size, weight, and cost of these devices, G
Reverse conduction type G in which TO and this anti-parallel diode are integrated
TO thyristors have been developed. Figure 3 shows reverse conduction type G.
An example of a cross-sectional structure of a To thyristor is shown. In FIG. 3, a GTO thyristor section 1 and a diode section 2 are separated by a separation section 8 and formed in an antiparallel layer structure on the same wafer. GTO thyristor section 1 has P emitter layer P9 and N
Base layer NB, P base layer PB, and divided N emitter layer NE
The diode section 2 is made up of 4 layers and 3 junctions, and the diode part 2 is made into one junction of the N layer of N layer, NB-, and the P layer of P8 and P'', the anode electrode 4 is made common, and the cathode electrodes 56 and 5D are connected by conductor. The gate electrode 6 is connected by wiring. 7 is a surface protection material such as passivation rubber. The circuit diagram of the reverse conduction type GTO thyristor with this structure is as shown in Figure 4.
The TO thyristor TH and the diode D are connected in antiparallel, and the gate of the GTO thyristor TH and the common cathode are short-circuited by the isolation resistor R of the isolation section 8. The separation resistance R of the separation portion 8 is formed as a sheet resistance of the core layer PB by digging a groove in the P base layer PB.

The turn-off operation of the reverse conduction type GTO thyristor with the above-mentioned configuration is performed by applying a reverse voltage between the gate G and the cathode. At this time, if the separation resistance R is not sufficiently large, a large voltage may occur between the gate and the cathode. Current flows. Therefore, the current IR in the separation resistor R generates heat due to a power loss of IR''·R, and this heat generation causes element deterioration and damage, and reduces the breaking ability of the GTO thyristor section.

Further, the gate circuit power supply requires a capacity capable of supplying a large amount of current flowing through the separation resistor R that does not contribute to on/off operations.

On the other hand, when the load current flows through the diode section 2, the GTO
When a forward voltage is applied to the thyristor section l, for example when a reverse conduction type GTO thyristor is used as a switching element of a voltage source inverter, the carriers accumulated in the diode section 2 pass through the separation resistor R and are transferred to the GTO thyristor section. This flow of carriers may act as a gate current, causing the GTO thyristor section 1 to fire incorrectly.

Due to the problems mentioned above, it is desirable to increase the resistance value of the isolation resistor R. To achieve this, it is possible to widen the groove width of the isolation section 8 or to deepen the groove, but the former is not possible. This lowers the area utilization rate of the element, and if the groove is made deeper, the problem remains that the off-breakdown voltage of the GTO XIRISK section 1 and the reverse breakdown voltage of the diode section 2 are reduced.

In order to solve this problem, a separation method using a bevel structure is proposed in Japanese Utility Model Application No. 63-92792. In this method, as shown in FIG. 5, grooves having a bevel structure are dug at the boundaries between the GTO section 1 and the diode section 2, and a separation section 18 is formed in which the grooves are filled with a surface protection material 9. The bevel structure allows the thyristor section and the diode to withstand voltages to be improved, and the GTo section and the diode section can be completely separated.

D1 Problems to be Solved by the Invention However, the separation method shown in FIG. 5 had the following drawbacks. That is, an enlarged view of the separating portion 18 is shown in FIG. 6 to explain: (1) Compared to the conventional method, grooves having a bevel structure must be formed at two locations, making the processing more complicated.

(2) Angle θ2 between the P layer surface and the groove (+ PP) Since the angle θ2 between the P layer surface and the groove is usually about 45°, the resulting processing width a increases the width of the separation part.

(3) The width C of the portion that is ineffective as an element due to processing increases the width of the separation portion. If this width C is not wide enough, the two grooves will interfere with each other, making accurate machining impossible.

(4) Due to items (2) and (3) above, the area utilization rate of the element decreases.

The present invention has been made in view of the above points, and its purpose is to:
It is an object of the present invention to provide a semiconductor device that increases the withstand voltage and area utilization rate of the device, and also simplifies the processing shape of the separating portion and shortens the processing time.

Means for Solving Problem E2 The present invention forms a GTO thyristor part and a diode part in an anti-parallel layer structure in the central part and peripheral part of a wafer, and
In a semiconductor device in which a common anode electrode and individual cathode electrodes and gate electrodes are provided in the O thyristor part and the diode part, the GTO thyristor part and the diode part have a PIN structure, and the boundary between the GTO thyristor part and the diode part has a PIN structure. , a first structure in which a portion of 415 or more on the side of the P base layer on the side surface of the N base layer and the side surface of the P base layer are formed at an angle of 90° ± 15° with respect to the bonding surface of the P base layer and the N base layer. a processed portion, and a second processed portion where the cross-sectional area of the element decreases as it goes toward the P emitter layer, extending from the portion following the first processed portion on the side surface of the N base layer to the N buffer layer and the P emitter layer; It is characterized by a structure in which a groove is dug and a separation portion is provided in the groove with a surface protection material filled therein.

Since both the F action GTO thyristor section and diode section have a PIN structure, on-voltage and switching loss are significantly improved. The angle forming the first processing part is 90°±1
5°, the width of the separation section is significantly narrower than in the conventional case. Therefore, the area utilization rate of the element is greatly improved. Since only one separation part is required, processing is easy and processing time is shortened.

G. Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional structural diagram showing one embodiment of the present invention,
The same parts as in FIG. 5 are indicated by the same reference numerals. 1st
In the figure, there is a diode section 2 in the center of the element on the same wafer.
is formed, and the GTO thyristor section 1 is formed at the peripheral edge thereof with a separation section 28 interposed therebetween. Both the GTO thyristor section (■) and the diode section 2 are composed of an N-balanced layer N.
It has an IN structure. Here, the isolation section 28 has a structure in which a groove is dug to provide a bevel structure at the boundary between the diode section 2 and the GTO thyristor section l, and the groove is filled with a surface protection material 9.

The separation portion 28 is formed by sandblasting or the like at the boundary between the diode portion 2 and the GTo thyristor portion l, with a bevel angle θ.
4. A single groove having an angle of θ2 is dug and the depth of the groove reaches or is close to the anode electrode 4, and the groove portion is filled with a surface protection material 9. The groove of the separation part 28 extends from the cathode electrode side of the element to the anode electrode 4 side, forming a first processed part A and a second processed part B.
have. As shown in the enlarged views of the separated part in FIGS. 1 and 2, the first processed part A is a part that occupies 415 or more from the P base layer PR side of the side surface of the N base layer No-, and a part of the P base layer PB. The side surfaces have the same inclination with respect to the joint surfaces of PB and N8-. Then, the angle θ1 between the inclination of the first processed portion A and the joint surfaces of PB and N8- is θ1. θ.

are each 90°±15°. Also, the second processing section B is N
The portion of the side surface of the base layer NB- that continues to the first processed portion A, the N-balance layer N, and the P emitter layer PE are inclined so that the cross-sectional area of the element 2 decreases as it moves toward the P9 side, that is, toward the bottom in the figure. ing. Then, the angle θ3. formed between the inclination of the second processed portion B and the joint surfaces of N8− and N. θ4 is 60°±20°. Here, the angle θ
1. If θ is set to a large negative angle, the effect of concentration of the electric field on the N′ layer side will occur, similar to the conventional base structure. Further, when θ1θ is set to a large positive angle, the electric field is not concentrated in the N′ layer, but the electric field strength in the P layer and the N − layer is not weakened much. So θ1. It has been experimentally confirmed that θ is approximately 90°±15° in order to prevent the electric field from concentrating on the N′ layer and weaken the electric field strength on the P and N− layers. Further, if the portion occupied by the first processed portion A is less than 415 from the PB layer side of the side surface of the NB- layer, the withstand voltage will decrease, so it is preferably 415 or more.

However, this first processing part A alone is insufficient, and further N
A second processed portion B is provided to weaken the electric field strength of the layer. This processed portion B increases the surface area of the N layer, and
The surface electric field strength of the layer is weakened. As mentioned above, the combination of processing part A and processing part B allows the PIN
The surface electric field strength of the high breakdown voltage element (reverse conduction type GTO thyristor in the embodiment) of the structure is sufficiently weakened, and the designed high breakdown voltage can be achieved.

Such a semiconductor element can be easily processed by using, for example, a sandblasting method. That is, a processed part A is obtained by applying a sandblasting nozzle perpendicularly or substantially perpendicularly to the element, and a processed part B is obtained by repelling sand from the nozzle on the anode electrode 4.

Here, the maximum off-voltage is 4500V, and the maximum breaking current is 300V.
A 0A reverse conduction type GTO thyristor was designed and prototyped using the conventional method and the method of the present invention. The anode diameter of the element is 88xuφ,
The separation section was approximately 17z11φ, and the two were compared.

(a) Comparison of processing methods In the conventional method, it is difficult to prevent the two grooves from being affected by each other, and the yield of the withstand voltage characteristics of the prototype devices was not as good as that of the method of the present invention. The method of the present invention could be easily achieved by using a sandblasting technique and applying the processing nozzle perpendicularly to the element. Since there is only one groove, the machining time was half that of the conventional method, and the yield of withstand voltage was also good.

(b) Comparison of separation widths 5 In the conventional method, the Si thickness is about 1Rm, so the width λ in FIG. 6 is about 1zz. Also, the groove width is 1mm, and the margin C between the grooves is 2
mm is also required. Therefore, in the conventional method, the separation width is 6ytt.
m is necessary. In the method of the present invention, the Si thickness is about 0.8H due to the adoption of the PIN structure, so the width a in FIG. 2 is about 0.2■. Also, the groove width is required to be 1.2 iu. Therefore, in the method of the present invention, a separation width of 1.6zz is required. As described above, the separation width could be narrowed by 4.4 ram by the method of the present invention.

If this is converted into area, an additional 4.7 cm' can be used as an element.

Due to the isolation section 28 having the above-described structure, the diode section 2 and the GTO thyristor section 1 are completely separated even though they are formed on the same wafer, and there is no short circuit between the gate and cathode due to the conventional isolation resistance R of the PB layer. This eliminates heat generation and wasteful gate power supply current, and further eliminates erroneous firing of the GTO thyristor section 1 due to diode carriers.

Note that the device configuration in the example shows a case in which the diode part is formed in the center, but the same result can be achieved even if the GTO thyristor part is formed in the center and the diode part is formed in the periphery. Effects can be obtained.

Effects of the Invention As described above, according to the present invention, the GTO thyristor section and the diode section have a PIN structure, and the first... Since the groove formed by the second processed portion is dug and filled with the surface protection material, the following excellent effects can be obtained.

(1) With only one groove, the GTO thyristor section and diode section can be completely separated, similar to the conventional method using two grooves.

(2) Since the current generated by the conventional separation resistor R is eliminated, element deterioration and damage caused by heat generated by the separation resistor and power loss of the gate power supply can be reduced (reduced capacity).

(3) Erroneous firing of the GTO thyristor section due to accumulated carriers in the diode section is eliminated.

(4) Since the GTO thyristor section and diode section have a PIN base structure, on-voltage and switch loss are significantly improved.

(5) The first processed part of the separation part is formed at an angle of 90°±15° with respect to the bonding surface of the P base layer and the N base layer, and the second processed part is formed so that the element Since the groove is formed so that the cross-sectional area of the groove is reduced, a high breakdown voltage can be simultaneously achieved for the GTO thyristor section and the diode section using only one groove.

(6) Compared to the conventional device shown in FIG. 5, for example, only one groove is required for the bevel structure, so processing is simple and processing time is shortened (l/2 compared to the conventional device).

In addition, the yield of withstand voltage characteristics is also good.

(7) The groove of the separation part is the first groove. Since it has the second processed portion, the processing width a (width a in FIG. 2) can be made narrower to about 215 mm compared to the conventional one (width a in FIG. 6).

(8) The width b of the groove (width b in FIG. 2) is only about half that of the conventional one (width b in FIG. 6) because there is only one groove.

9 (9) There are no invalid parts as a device due to processing.

(10) Compared to the conventional separation method, the separation width is reduced to 1
/3 or less.

This significantly improves the area utilization of the device.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional structural diagram showing an embodiment of the present invention, FIG. 2 is an enlarged view of the separated part of the embodiment, and FIG. 3 is a cross-sectional structural diagram of a conventional example.
Fig. 4 is a circuit diagram of a reverse conduction type GTO thyristor, Fig. 5 is a cross-sectional structure diagram of a semiconductor element having a conventional bevel groove, and Fig. 6 is a circuit diagram of a reverse conduction type GTO thyristor.
The figure is an enlarged view of an isolation part of a conventional semiconductor element having a bevel groove. 1...GTO thyristor section, 2. diode section, 4
Anode electrode, 5D, 5c, cathode electrode, 60 gate electrode, surface protection material, 8゜18゜28...separation section, N buffer layer. 2 people outside 03

Claims (1)

[Claims] (1) A GTO thyristor section and a diode section were formed in an antiparallel layer structure in the center and periphery of the wafer, and a common anode electrode and individual cathode electrodes and gate electrodes were provided for the GTO thyristor section and diode section. In the semiconductor device, the GTO thyristor section and the diode section have a PIN structure, and at the boundary between the GTO thyristor section and the diode section, 4/5 or more of the side surface of the N base layer on the P base layer side and the side surface of the P base layer. and a first processed portion formed at an angle of 90° ± 15° with respect to the bonding surface of the P base layer and the N base layer, and a portion continuing from the first processed portion on the side surface of the N base layer. A groove is dug across the N buffer layer and the P emitter layer and has a second processed portion in which the cross-sectional area of the element decreases toward the P emitter layer, and this groove is filled with a surface protection material. A semiconductor device characterized by a structure in which a separation section is provided.