JPS60157257A - Processing method of end surface inclination for semiconductor element - Google Patents

Abstract

PURPOSE:To improve the control accuracy for the formation of angles by making the grinding speeds of an Si wafer in the upper and lower sides the same with respect to a direction of spraying by a method wherein the direction of spraying abrasive and the surface to be abraded are put almost at a right angle. CONSTITUTION:A semiconductor element consisting of an Si wafer 1 and an Mo plate 2 is inserted to a rotary jig 4 and ground by means of a grindstone 5 so that the upper area may become smaller than the lower area. The angle of this grinding is set at an angle theta3 obtained by subtracting the difference DELTAtheta between an angle theta1 of spraying abrasive and the angle of inclination after grinding, with respect to the angle resulting from addition of 90 deg. to the angle of end surface inclination of the wafer 1 at the final step. Then, the abrasive is sprayed rectangularly to the ground surface. Thereby, the grinding speeds of the water 1 in the upper and lower sides becomes almost the same with respect to the direction of spraying; therefore, the control of the angle of Si inclination in the neighborhood of a junction that inhibits a forward voltage is facilitated, an its accuracy improves.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention provides a semiconductor substrate having two principal surfaces, such that the area of the principal surface in contact with the supporting substrate is smaller than the area of the other principal surface. The present invention relates to a method of processing a semiconductor element to provide a beveled end face.

[Prior art]

In order to increase the controllable current in a high-voltage, large-capacity gate turn-off thyristor (GTO) with a pnpn structure,
Since it is necessary to reduce the impurity concentration in the p base region,
It is difficult to increase the forward breakdown voltage compared to general thyristors. There are many cases where reverse breakdown voltage is not necessary due to the circuit configuration. In this case, since only the forward breakdown voltage can be increased to the stockout breakdown voltage, it is preferable to use a positive bevel structure for the joint to prevent forward breakdown voltage and to increase the breakdown voltage. However, in order to increase mechanical strength and alleviate stress caused by heat cycles in high-power semiconductor devices, a support substrate made of molybdenum or tungsten is generally brazed to a semiconductor substrate made of silicon or the like. As a result, the physical symmetry near the top and bottom surfaces of the silicon wafer is lost, resulting in different grinding speeds.

FIGS. 1(a) and 1(b) are explanatory diagrams showing a conventional end face grinding method, in which 1 is a semiconductor substrate (hereinafter referred to as a silicon wafer), 2 is a support substrate (hereinafter referred to as a molybdenum plate), and both of them are used to form a semiconductor element. is formed.

3 is a nozzle for spraying abrasive material, and 4 is a rotating jig for rotating the semiconductor element. Note that the arrows indicate the flow of the abrasive material. The manufacturing process will be explained below.

First, silicon wafer 12. A semiconductor element made of a molybdenum plate 2 is placed on the surface of a silicon wafer 1, and the abrasive material is sprayed from the outer periphery of the semiconductor element toward the rotation center O while the semiconductor element is inserted into a rotating jig 4 and rotated. Maybe nozzle 3.
The end surface of the silicon wafer 1 is beveled by jetting an abrasive material.

However, in the above method, since the angle θ between the direction in which the abrasive is sprayed and the surface to be polished is small, the abrasive is sprayed on the upper and lower sides of the silicon wafer 1 in the direction. Because the grinding speed of the molybdenum plate 2 is significantly different from that of the silicon wafer IK, and because the grinding speed of the molybdenum plate 2 is significantly lower than that of the silicon wafer IK, the grinding speed near the bottom surface of the silicon wafer 1 is significantly lower due to the reflection of the abrasive from the surface of the molybdenum plate 20. There was a drawback that it was difficult to obtain a desired inclination angle due to the increase in size, etc. In other words, FIGS. 2(a) and 2(b) show the time course of the end face shape.

(e) As you can see, the inclination angle θ2 near the J22 eclipse
On the other hand, on the bottom surface of the silicon wafer 1, the 1 bite d is large, so the uniformity of the surface electric field is lost.
There was a drawback that good withstand voltage characteristics could not be obtained.

[Summary of the invention]

This invention was made in order to eliminate the above-mentioned drawbacks of the conventional ones.The direction of the abrasive spray is made almost perpendicular to the surface to be polished. The present invention provides a method for machining an end face of a semiconductor device with an inclined end face, in which the grinding speed on the upper and lower sides of the semiconductor device is made the same, and the control accuracy of angle formation is improved.

[Embodiments of the invention]

FIGS. 3(&) to 3(d) are process explanatory diagrams of an end face grinding method showing an embodiment of the present invention. In this figure, 1 to 4 are the first
The same thing as in the figure is shown, and 5 is a grindstone for grinding the silicon wafer 1.

In this embodiment, first, as shown in FIG. 3(a), a silicon wafer 1. A semiconductor element made of a molybdenum plate 2 is inserted into a rotating jig 4 with the silicon wafer 10 side facing up, and a grindstone 5 is used so that the area of the upper surface of the silicon wafer 1 is smaller than the area of the lower surface as shown in FIG. 3 (b). ) to grind. This grinding angle is an angle obtained by subtracting the difference Δθ between the inclination angles of the silicon wafer 1 after grinding and the angle θ at which the abrasive is sprayed with respect to the final end face inclination angle lcc + o'v of the silicon wafer 1. It is preferable to set it to θ. Thereafter, as shown in FIG. 3(c), an abrasive material is sprayed at right angles to the ground surface formed in the step of FIG. 3(b). In this case, since the grinding speed of the upper and lower sides of the silicon cube 1 is almost the same in the direction of spraying, the silicon inclination angle θ near the junction J (see FIG. 4) that blocks forward voltage.

This makes it easier to control and improves its accuracy. This is the third
Shown in Figure (d).

For example, if the target pump dip bevel angle '1 is 60 degrees, the grinding angle θ3 in the step of FIG. 3(b) is 60 degrees + 90 degrees - 15 degrees = 1
35°, and for the grinding process in Fig. 3(e), the spray angle of the nozzle 3 is set at the angle θ, 760° - 15° = 4
Set to 5°. Incidentally, the time course of the grinding shape of the end face of the silicon wafer 1 in each step of FIGS. 3(b) and 3(c) is shown in FIGS. 4(a) and 4(b).

As can be seen from this figure, the junction J that blocks the forward voltage
Since the inclination angle around 2 can be easily and accurately controlled and the grinding time can be shortened, the lower surface of the silicon wafer 1 does not need to be ground excessively.

The shape after grinding is sharp and very good.

〔Effect of the invention〕

As explained above, the present invention includes a step of processing the end face of the semiconductor element into an inclined surface so that the lower surface of the semiconductor element of a semiconductor element having a semiconductor substrate and a supporting substrate is thicker than the area of the upper surface, and This process involves the process of "grinding" the semiconductor substrate while spraying the abrasive powder almost perpendicularly to the inclined surface, which facilitates control of the inclination angle of the silicon wafer near the bonding surface to block forward voltage. In addition, since it is possible to make the surface electric field distribution uniform, it has advantages such as good withstand voltage characteristics.

[Brief explanation of drawings]

Figures 1 (, ) and (b) are explanatory diagrams showing the conventional end face grinding method, Figures 2 (a), (b) and (c) are diagrams showing the time course of the end face shape, and Figure 3 ( a) to (d) are process explanatory diagrams of an end face grinding method showing one embodiment of the present invention, and FIG.
) and (b) are diagrams showing the time course of the end face shape in the embodiment of FIG. 3. In the figure, 1 is a silicon wafer, 2 is a molybdenum plate, 3 is a nozzle, 4 is a rotating jig, and 5 is a grindstone. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa (2 others) Figure 1 (a) (b) Figure 2 (a) (a (b) Figure 3 Figure 4 (a) Procedural amendment (voluntary) Dear Commissioner of the Japan Patent Office 1. Indication of the case Japanese Patent Application No. 59-013717 2. Title of the invention 3. Processing method for tilting the end face of a semiconductor device 3. Person making the amendment 5. Claims column 9 of the specification to be amended 9. Details of the invention Explanation column, drawing 6, content of amendment + 11 The claims of the specification are amended as shown in the attached sheet.
Correct as "positive bevel". (3) Correct the code 1 in Figure 3(b) to 5 as the attached sheet has not been distributed. Above 2, claims include a semiconductor element in which the one main surface of a semiconductor substrate having at least two main surfaces is brazed to a support substrate; When processing the end face of the semiconductor substrate to be inclined so that the area of the main surface is smaller than the area of the other main surfaces, the area of the two main surfaces of the semiconductor substrate that contacts the support substrate is An end face of a semiconductor element comprising: a step of grinding the end face to be larger than the main face; and a step of grinding while spraying abrasive powder substantially perpendicularly to the inclined surface of the end face formed by this step. Beveled processing method.

Claims (1)

[Claims] In a semiconductor element in which one main surface of a semiconductor substrate having at least two main surfaces is brazed to a support substrate, the area of the main surface in contact with the support substrate among the two main surfaces of the semiconductor substrate is larger than the other main surface. a step of making an area of the two main surfaces of the semiconductor substrate that contacts the supporting substrate larger than the other main surface when processing the end surface of the semiconductor substrate to be inclined so that the end surface is smaller than the area of the main surface; 7. A method for processing a semiconductor element with an inclined end surface, comprising the steps of: 7. Grinding while spraying abrasive powder substantially perpendicularly to the inclined surface of the end surface formed in this step.