JP3253372B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device having a positive bevel.

[0002]

2. Description of the Related Art In a power semiconductor device such as a high-breakdown-voltage gate turn-off thyristor (hereinafter abbreviated as a high-breakdown-voltage GTO), a positive bevel structure is adopted so that a depletion layer on the surface of a silicon semiconductor substrate is expanded as much as possible. . FIG. 5 shows an example of a semiconductor device having this structure.
In FIG. 5, four layers of PNPN are formed on a silicon semiconductor substrate 1 through a well-known diffusion process and the like, and a high breakdown voltage GTO is formed.
It has a structure. On one main surface side of the silicon semiconductor substrate 1, a temperature compensating plate 2 serving as an anode electrode is made of an alloy.
It is fixed. On the other main surface side of the silicon semiconductor substrate 1, a temperature compensating plate 3 serving as a cathode electrode is mounted. A bevel groove 4 is cut at a predetermined angle (bevel angle) from the other main surface of the silicon semiconductor substrate 1. As this bevel processing method, sand blast method,
There is a cutting method using a diamond saw, etc., and the bevel groove 4 is formed by these methods in order to widen the depletion layer at the PN junction.

[0003]

Heretofore, the following problems have conventionally been encountered because the above-described bevel groove 4 is generally formed by a sandblasting method or a cutting method using a diamond saw. That is, in the case of forming a bevel groove 4 I'm sandblast method, there is a shape instability by rebound or the like of the abrasive material used for implementing the method, as shown in FIG. 6, the rim of the bevel groove 4 Department
5A and 5B had a disadvantage . In the cutting method using a diamond saw, no abnormality is observed from the surface due to chipping or wear of the diamond saw, but a saw mark 6 is provided inside the bevel groove 4 as shown in FIG. Is formed, or the cleavage portion 7 is generated. Therefore, there is a problem to be solved that an abnormal electric field distribution occurs when a high voltage is applied, and the semiconductor device is easily broken.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has no fear that a saw mark or a cleavage portion is formed in a bevel groove, and an abnormal electric field distribution even when a high voltage is applied. It is an object of the present invention to provide a method of manufacturing a semiconductor device capable of maintaining high breakdown voltage and high reliability stably for a long time without causing the problem.

[0007]

A first method of manufacturing a semiconductor device according to the present invention is directed to a method of manufacturing a semiconductor device having a positive bevel structure, wherein an end surface of the silicon semiconductor substrate has an inclination angle smaller than a bevel angle of the end surface. After bonding the semiconductor substrate and the semiconductor substrate with the temperature compensating plate inclined,
The end face of the semiconductor substrate is beveled by a polishing means. The second method of manufacturing a semiconductor device of the present invention is a method of manufacturing a semiconductor device having a positive bevel structure, it is inclined end face so as to have a smaller inclination angle than the bevel angle of the silicon semiconductor substrate end face and the end face Steps are formed continuously on the inclined surface of
After the formed temperature compensating plate is alloyed and fixed to the semiconductor substrate, the end face of the semiconductor substrate is beveled by a polishing means.

[0008]

In the first and second manufacturing methods of the semiconductor device according to the present invention, since the end surface of the temperature compensating plate is given a predetermined inclination angle in advance, an extremely smooth inclined surface is formed by the polishing means. Thus, breakdown of the semiconductor device due to electric field concentration can be avoided, and high breakdown voltage and high reliability can be maintained for a long time.

[0009]

Embodiments of the present invention will be described below. In the present invention, as shown in FIG. 1, the outer peripheral surface of a temperature compensating plate 2 made of molybdenum or the like to be alloyed and fixed to a silicon semiconductor substrate 1 via an aluminum foil 8 is processed in advance so as to be an inclined surface 2a. It is characterized by the following. Here, the inclination angle given by the inclination processing is set to θ1. Next, the temperature compensating plate 2 is alloyed and fixed via the aluminum foil 2 as usual. Thereafter, for example, the silicon semiconductor substrate 1 is supplied while supplying an abrasive 10 using a beveling dish 9 used at the time of lens polishing as shown in FIG.
Is polished so as to have a predetermined inclination angle θ2. In this case, since θ1 <θ2, the outer peripheral surface of the temperature compensating plate 2 does not contact the inner wall of the beveling plate 9, so that only the end surface of the silicon semiconductor substrate 1 can be a smooth beveled surface 1a.

FIG. 3 shows a semiconductor device after processing the silicon semiconductor substrate 1 by the above method. This semiconductor device
It is a high breakdown voltage GTO having a four-layer structure of a PE layer, an NB layer, a PB layer, and an NE layer. In the figure, 11 is the NB from the PE layer .
An anode short portion formed by selective diffusion so as to penetrate the layer . Further, the above-mentioned inclination angle θ1 is appropriately determined depending on the thickness of the temperature compensating plate.
In the case of the embodiment, θ1 <40 degrees. In this case, the inclination angle θ2 of the silicon semiconductor substrate 1 by beveling was set to 45 degrees. As described above, the desired inclination angle θ2 can be given to the outer peripheral surface of the silicon semiconductor substrate 1, and unlike the conventional formation of bevel grooves by cutting, extremely smooth end surface polishing can be performed. Destruction of the semiconductor device due to concentration is effectively prevented. Next, a second embodiment of the present invention is shown in FIG. In this embodiment, a step portion 2b is formed on the outer peripheral surface of the temperature compensating plate 2 continuously with the inclined surface 2a having the inclination angle θ1, so that the relief of the beveling plate 9 from the curved inner peripheral surface is made larger. It is. Also in this case, there is a relationship of θ1 <θ2. Thereby, there is an advantage that polishing of the end face of the silicon semiconductor substrate 1 becomes easy. In the first and second embodiments, the method using the beveling plate 9 as the end surface polishing means of the silicon semiconductor substrate 1 has been described.
Other polishing means that can finish the surface smoothly without necessarily using a beveling dish may be used.

[0011]

As described above, according to the present invention, in a method of manufacturing a semiconductor device having a positive bevel structure, a temperature compensating plate whose end face is inclined to an angle smaller than the bevel angle of a silicon semiconductor substrate, or a similar end face is used. Tilt
After the temperature compensating plate having a stepped portion formed on the outer periphery is alloyed and fixed, the end face of the silicon semiconductor substrate is beveled by a polishing means such as a beveling dish, so that the surface has a very smooth slope. A surface can be formed, the semiconductor device can be prevented from being broken due to electric field concentration, and a semiconductor device which can maintain high breakdown voltage and high reliability for a long time can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view showing a first embodiment in which an outer peripheral portion of a temperature compensating plate is provided with an inclination angle in order to carry out a method of manufacturing a semiconductor device of the present invention.

FIG. 2 is a cross-sectional view showing a state in which a polishing process is performed using a beveling dish in order to give an inclination angle to an end surface of a silicon semiconductor substrate on which the temperature compensation plate is alloyed and fixed.

FIG. 3 is a side view of the semiconductor device after being polished by a beveling dish.

FIG. 4 is a side view of a second embodiment of the present invention in which an inclination angle and a step portion are provided on an outer peripheral surface of a temperature compensating plate.

FIG. 5 is a side view for explaining a conventional bevel processing method.

FIG. 6 is a side view for explaining the droop of a bevel groove formed by a conventional sandblast method.

Figure 7 shows a side view for explaining a saw marks and cleavage of a conventional cutting method thus formed bevel groove.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Silicon semiconductor substrate 1a Bevel processing surface 2 Temperature compensator 2a Inclined surface 3 Temperature compensator 4 Edge of bevel groove 5a, 5b 6 Saw mark 7 Cleavage part 8 Aluminum foil 9 Beveling dish 10 Abrasive material Outer peripheral surface of temperature compensator 2 The bevel angle attached to the outer peripheral surface of the silicon semiconductor substrate 1

Claims (2)

(57) [Claims] In a method of manufacturing a semiconductor device having a positive bevel structure, a temperature compensating plate whose end surface is inclined so as to have an inclination angle smaller than a bevel angle of an end surface of a silicon semiconductor substrate is alloyed and fixed to the semiconductor substrate. And then subjecting the end face of the semiconductor substrate to beveling processing by a polishing means. 2. A method of manufacturing a semiconductor device having a positive bevel structure, comprising: tilting an end surface of a silicon semiconductor substrate so as to have an inclination angle smaller than a bevel angle of the end surface;
2. The semiconductor device according to claim 1, wherein a temperature compensating plate having a step portion formed continuously on the slope is alloyed and fixed to the semiconductor substrate, and then the end surface of the semiconductor substrate is beveled by polishing means. Manufacturing method.