JPS60197367A - Preparation of mirror-surface wafer - Google Patents

Abstract

PURPOSE:To prepare a wafer which has a mirror surface on one-side surface has a large diameter with high precision by making difference in the polishing speed between on one surface and the other surface of the wafer interposed between the lower and the upper surface plates which revolve in the opposite direction and making one surface into mirror surface and the other surface into semipolished surface. CONSTITUTION:When the number of revolution of an internal gear 15 is 12rpm clockwise and the number of revolution of a sun gear 14 is 10rpm clockwise, a carrier 16 revolves 10.9rpm clockwise. Therefore, when polishing for a wafer is carried-out with the number of revolution of a lower surface plate 11 in 11rpm clockwise and the number of revolution of an upper surface plate 13 in 50rpm counterclockwise, the ratio between the speed difference between the upper surface of a wafer 17-upper surface plate 13 and the speed difference between the undersurface of the wafer 17-lower surface plate 11 becomes 510:1. Since the environment during machining is equal in the vertical direction, the ratio of the speed difference becomes nearly equal to the ratio of working speed on the upper and lower surfaces of the wafer 17, and only the upper surface of the wafer 17 is made mirror surface, and the undersurface is made semipolished surface. Therefore, even if the wafer 17 is made to a large diameter, a wafer having a mirror surface on one-side surface can be prepared with high precision similarly in the conventional method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for manufacturing mirror-finished wafers using a double-sided boring machine.

Conventionally, mirror polishing of wafers such as silicon is usually performed using a single-sided polishing machine.

As shown in Fig. 1, the wafer 2 is pasted on a pasting plate l using wax or a suction pad for pasting, and this is attached to the pressure head 3, and the surface of the rotating polylang table 4 is Polishing is performed on one side using a polishing cloth 5.

However, in this method, the attachment plate 1 of the pressure head 3
The pressure condition on the contact surface with the wafer 2, the flatness of the pasting plate 1, the pasting accuracy of the wafer 2, or the polishing table 4.
The flatness of the wafer and its temperature deformation affect the mirror surface precision of the polished wafer, making it difficult to process the wafer with high precision. Further, even if these could be improved technically, there is a limit to the mirror surface accuracy of the wafer, and it is not possible to cope with the increase in the diameter of the wafer.

On the other hand, double-sided polishing devices are attracting attention as high-precision processing devices. In this method, a wafer is held and sandwiched between a lower surface plate and an upper surface plate by a rotating carrier that meshes with a sun gear and an internal gear, and both sides of the wafer are simultaneously bored.

However, double-sided mirror wafers manufactured using this method have the problem that the wafers adhere to each other during heat treatment in the device manufacturing process, and they do not meet the needs of users, and with the exception of exceptional cases, they are not commercially available. It wasn't worth it.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for producing a single-sided mirror-finished weno sheet with a large diameter and high precision.

That is, in the method for manufacturing a mirror-finished wafer of the present invention, when manufacturing a mirror-finished wafer by sandwiching the wafer between a lower surface plate and an upper surface plate that rotate in opposite directions and performing boring, one surface and the other surface of the wafer are It is characterized by giving a difference in the polishing speed of the two surfaces, and making the negative surface a mirror surface and the other surface a semi-glossy surface.

According to such a method, even if the diameter of the wafer is increased, it is possible to manufacture a wafer with high precision, which has the same external appearance as a single-sided mirror-finished wafer manufactured using a conventional single-sided polishing apparatus.

Hereinafter, embodiments of the present invention will be described with reference to FIG.

FIG. 2 is a sectional view of the double-sided boring machine.

In the figure, reference numeral 11 denotes a lower surface plate, and a rotating shaft 12 is inserted into the central opening of this lower surface plate 11. The center opening of the upper surface plate 13 is fitted into the upper end portion 12a of this rotating shaft 12. In addition, a sun gear i4 is provided between the lower surface plate 11 and the outer circumference of the rotating shaft 12.
is installed.

Furthermore, an internal gear 15 is disposed around the outer periphery of the lower leg 5111. Furthermore, a sun gear 14 is placed on the lower surface plate 11.
A plurality of carriers 1 meshing with and internal gear 15
6. . . are stored, and the wafers 17, . . . are held by these carriers 16, .

Using the above-mentioned double-sided boring machine, for example, the rotation speed of the internal gear 15 is set to 12 rpm clockwise, and the sun gear 1 is rotated clockwise.
4 rotate clockwise as l Orpm, the carriers 16, . . . revolve clockwise at a rotation speed of 10.9 rpm. My legs are in this state! The wafer was polished by setting the rotation speed of the upper surface plate 13 to 11 rpm clockwise and 5 Orpm counterclockwise.

Under the above conditions, if we consider the revolution speed of the carriers 16,... to be the speed of the wafers 17,..., then the top surface of the sea urchin/\17 -
Speed difference between upper surface plate 13 and sea urchin/\17 Lower surface - lower surface plate 11
The ratio with the speed difference between them is 510:l.

Since the atmosphere during processing is the same on the upper and lower sides, the ratio of the speed difference is approximately equal to the ratio of the processing speeds on both the upper and lower surfaces of the wafers 17, . As a result, only the upper surface of the sea urchin/\17, . . . can be made into a mirror surface, and the lower surface can be made into a semi-glossy surface.

Therefore, even if the diameter of the wafers 17, .

For example, the processing temperature is 30℃, the pressure is 300g 7cm2, and the rotation speed is 125f under the same conditions as above.
When a wafer with a diameter of f1 was polished, the top surface, which had a high polishing speed, was polished by 20 #Lm and became a mirror surface, and the bottom surface was polished by only 0.04Ji, m and had a semi-glossy surface.

In the case of a wafer with a diameter of 125 mm, which has strict flatness standards as mentioned above, for example, a mirror-finished wafer with a flatness within the standard of 3 pm is
In order to obtain 0 sheets, 50 to 60 sheets were required to be processed using the conventional method using a single-sided boring machine, but with the method of the above embodiment, only 10 to 15 sheets were processed. Moreover, by using a double-sided boring machine, the level of flatness of mirror-finished wafers was improved by 30-40%. Furthermore, although the past required a highly accurate pasting technique, the method of the present invention eliminates this need.

In addition, as in the above example, the bollising speed ratio was set to 510:
1, the infrared transmittance of the wafer is 10%, and the surface roughness is 0.5 to 1.0 JLta in Rmax, but the bolling speed ratio may be 20:1 or more.

This means that the infrared transmittance of conventional single-sided mirror wafers is 50%.
Below, the surface roughness is 0.1 to 2.0 g in R+sax.
Therefore, in order to achieve this range, the borizing speed ratio should be set to 20:1 or more. Also, in the following explanation, when the top surface of the wafer is a mirror surface and the bottom surface is a semi-glossy surface, However, the lower surface may be a mirror surface and the upper surface may be a semi-glossy surface.

As described in detail above, the method for manufacturing and distributing mirror-finished wafers of the present invention has extremely remarkable effects such as being able to manufacture large-diameter, high-precision, single-sided mirror-finished wafers with high efficiency.

[Brief explanation of the drawing]

FIG. 1 is a front view of a conventional single-sided polishing device, and FIG. 2 is a sectional view of a double-sided polishing device used in an embodiment of the present invention. DESCRIPTION OF SYMBOLS 11... Lower surface plate, 12... Rotating shaft, 13... Upper surface plate, 14... Sun gear, 15... Internal gear, 16... Carrier, 17... Wafer. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (4)

[Claims] (1) When manufacturing a mirror-finished wafer by sandwiching and polishing a wafer between a lower surface plate and an upper surface plate that rotate in opposite directions, giving a difference in polishing speed between one side and the other side of the wafer, - A method for manufacturing a mirror-finished wafer, characterized in that one surface is made into a mirror surface and the other surface is made into a semi-glossy surface. (2) The method for manufacturing a mirror-finished wafer according to claim 1, wherein the ratio of polishing speeds is 20:1 or more. (3) The method for manufacturing a mirror-finished wafer according to claim 1, wherein the infrared transmittance of the semi-glossy surface of the wafer is 50% or less. (4) The surface roughness of the semi-glossy surface of the wafer is 0 in Rmax
．． 1. The method for manufacturing a mirror-finished wafer according to claim 1, wherein the wafer has a grain size of 1 to 2.0 gm.