JPS62120973A - Two-side simultaneous lapping method for gaas wafer - Google Patents

Abstract

PURPOSE:To provide easier manufacture of GaAs wafer with precision and less amount of warp by mixing a grinding liquid incl. abrasive grains for lapping with an etching liquid having effect to dissolve GaAs chemically between the upper and lower surface reference boards. CONSTITUTION:Each GaAs wafer is nipped by an upper and a lower surface reference board for lapping which operate at different revolving speeds, and both sides of the ware are lapped simultaneously. The processing distortion layer generated at the surface of the GaAs wafer in the course of said lapping operation is dissolved by the etching liquid contained in the grinding liquid while it serves grinding with abrasive grains contained therein, and then is removed to relieve stresses at the surface of wafer, which should contribute to reduction of a warp otherwise generated there. At this time, the ratio of the mechanical grinding speed by the abrasive grains for lapping to the chemical dissolution speed by etching liquid shall preferably the approximately ten to one.

Description

BACKGROUND AND OBJECTS OF THE INVENTION The present invention relates to a method for simultaneously lapping both sides of a GaAs wafer.

Traditionally, the method of lapping both sides of a wafer at the same time is faster than the single-side lapping method, which involves bonding the wafer to a plate.
Due to the excellent dimensional accuracy of the finished wafer thickness,
For example, this is the most commonly used method for 3i wafers.

However, when a GaAs wafer is simultaneously lapped on both sides using a similar method, large warpage occurs in the wafer. This is caused by processing distortion caused by the mechanical action of the lapping abrasive grains.In the case of GaAs, the crystalline anisotropy is strong, and (100) wafers, which are generally used for devices, etc. , orthogonal [OT T
When the (100) plane is used as the reference plane for the 1 direction and the [OT1] direction, the curvature becomes a so-called saddle-shaped curvature that is curved in mutually opposite directions. In general, in the simultaneous double-sided wafer lapping method, the wafer is not particularly fixed, so
The above-mentioned warping phenomenon based on the downward strain occurring during the polishing action increases as the polishing M increases. For example, diameter 5
For an n-type GaAs wafer with a thickness of 0 m and a thickness of 450 μm, the warpage is increased by about 0.1 m for double-sided polishing of 41 μm.

The cause of warpage is mechanically applied stress, and even if processing conditions such as the size of the abrasive grains, processing pressure, and rotation speed of the upper and lower surface plates for lapping are adjusted, it will not work industrially. In order to obtain an effective lapping speed of 0.5 to 20 μm/min, the warping phenomenon described above cannot be avoided.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for simultaneously lapping both sides of a GaAs wafer, which solves the above-mentioned difficulties and can obtain a GaAs wafer with less warpage and high dimensional accuracy.

[Summary of the Invention] The present invention provides a method for simultaneously lapping both sides of a GaAs wafer in which the GaAs wafer is sandwiched between an upper surface plate and a lower surface plate for lapping, each having a different rotation speed. This is characterized in that a polishing liquid containing lapping abrasive grains mixed in an etching liquid having the effect of chemically dissolving GaAs is interposed between the polishing plate and the surface plate.

The present invention eliminates stress on the wafer surface and reduces warping by dissolving and removing a strained layer generated on the surface of a GaAs wafer during the lapping operation using an etching solution in the polishing solution while the polishing operation is in progress. It is. Therefore,
The present invention is not limited by the particle size of the lapping abrasive grains used or the type of etching solution used, nor is it limited by the structure, material, etc. of the lapping I device.

In order to carry out the present invention effectively, it is desirable that the ratio of the mechanical grinding speed by the lapping abrasive grains to the scientific dissolution rate by the etching liquid be approximately 10:1 in the lapping action. The figure shows the relationship between the etching speed at a lapping speed of 10 μm/min and the warpage size.

[Example] In this example, a double-sided wrapping device with a diameter of 63 mm is used.
A three-way system was used, which had an upper surface plate and a lower surface plate made of glass with a length of 0 m, and consisted of a center gear and a sun gear that rotated a carrier holding the wafer. GaAs wafer material has a thickness of 500μ
A Si-doped, n-type (100) wafer with a diameter of 50#I was used. Six of the above wafers are placed on one carrier, five carriers are placed on the lapping device, the upper surface plate is gently lowered, the above wafer is held between it and the lower surface plate, and the wafers are placed at 1000 wafers. A pressure of /cm2 was applied. As a polishing liquid, fine alumina powder with a particle size of 5 μm, deionized water, aqueous ammonia, and hydrogen peroxide were mixed in a ratio of 2:10 by weight.
The mixture at a ratio of :2:1 was poured between the upper surface plate and the lower surface plate, and the lower surface plate was rotated at a rotation speed of 15 rpn+ and the upper surface plate at a rotation speed of 5 ROM. Then, when the thickness of the wafer reached 400 μm, the rotation of the surface plate was stopped and the lapping operation was completed, and the warpage of the wafer was measured by the interference fringe method and was found to be 6 μm or less.

Further, after this wafer was dissolved by 5 μm on each side with an etching solution having a volume ratio of ammonia water, hydrogen peroxide solution, and water of 2:1:5, the warpage m was measured again and found to be 4 μm or less.

As a comparative example, the same equipment as in the above example was used, and the polishing liquid was alumina fine powder with a particle size of 5 μm and deionized water.
When lapping was performed in the same manner as in the above example using a mixture having a weight/fd ratio of 1=5 and the same rotational speed and pressure as in the above example, the warp M of the wafer was as large as 15 μm.

[Effects of the Invention] As described above, according to the present invention, excellent industrial effects can be achieved in that GaAs wafers with less warpage and high dimensional accuracy can be easily manufactured.

[Brief explanation of drawings]

The figure shows a wrapping speed of 10 μm/1 according to an embodiment of the present invention.
FIG. 3 is a diagram showing the relationship between the etching speed and the warpage size in minutes.

Claims (2)

[Claims] (1) In a simultaneous lapping method for both sides of a GaAs wafer, in which the GaAs wafer is sandwiched between an upper surface plate and a lower surface plate for lapping, each having a different rotational speed, there is a gap between the upper surface plate and the lower surface plate. A method for simultaneously lapping both sides of a GaAs wafer, characterized by interposing a polishing liquid in which lapping abrasive grains are mixed into an etching liquid that has the effect of chemically dissolving GaAs. (2) The GaAs according to claim 1, wherein the etching solution contains aqueous ammonia and aqueous hydrogen peroxide.
A method for simultaneously lapping both sides of a wafer.