JPS6317590B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wafer wrapping method for polishing the surface of a wafer using abrasive grains.

When performing microfabrication of wafers, wafer warpage is very important, and the establishment of methods for reducing these is attracting attention as an extremely important problem. These problems become more severe as the diameter of the wafer becomes larger.

The wafer processing process is approximately as follows. First, the grown crystal is sliced, then lapped, etched to remove the damaged layer, and finally polished for a final finish. It is generally said that if a sliced wafer has a large degree of warpage, the warpage will remain even after the final processing step is completed, and the warpage will remain large even after the element manufacturing process. Therefore, it has been pointed out that wafer slicing is the most important factor.

Conventionally, a wafer wrapping method has been used in which only double-sided simultaneous wrapping is performed. In this case, the wafer is sandwiched between the wrapping surface plates having a planar shape from above and below perpendicular to the surface, and is pressed and wrapped in a flat state.
Regardless of the amount of warpage of the wafer, the warp of the sliced wafer cannot be reduced even if wrapping is performed.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of conventional methods and to provide wrapped wafers with a uniform thickness and less warpage, regardless of the size of the warp in the sliced wafer.

The feature of the present invention is that the warpage of the wafer is removed by performing single-sided wrapping on a wafer that has been subjected to double-sided wrapping, and the resulting variation in thickness is removed by double-sided wrapping again.

According to the present invention, regardless of the amount of warpage of the sliced wafer, it is possible to obtain a wafer that is not warped and has a uniform thickness after wrapping.

An embodiment of the present invention will be described below.

FIG. 1 shows a wafer that was initially subjected to simultaneous double-sided wrapping to remove the slice strain layer of the sliced wafer. Next, Fig. 2 shows a wafer in which the convex surface of the wafer is bonded to an adhesive surface plate and the concave surface is wrapped on one side, without deforming the wafer, in order to eliminate the warpage of the wafer shown in Fig. 1. show. The broken line in the figure shows the shape of the wafer before single-sided wrapping, and the solid line shows the shape of the wafer after single-sided wrapping. FIG. 3 shows the wafer peeled off from the adhesive surface plate after single-sided wrapping. FIG. 4 shows a wrapped wafer with uniform thickness and no warpage, which is obtained by simultaneously wrapping both sides of the wafer in order to eliminate the variation in wafer thickness shown in FIG. 3.

Next, an example of the results of implementing the present invention will be described.

The wafer has a diameter of 76 mm, a thickness of 650 μm, and a warpage of 15 μm.
A sliced silicon wafer was used. Lapping was performed using alumina abrasive grains with a grain size of 10 μm at a rotation speed of 50 rpm.

First, wrap both sides at the same time for 10 minutes at a pressure of 60gr/
After wrapping 30 μm on ^both sides of the wafer and removing the slicing strain layer, place the wafer convex side down on an adhesive surface plate, and place a 100 μm wrapper on both sides of the wafer in the gap between the convex surface of the wafer and the adhesive surface plate. The wafer is bonded to the adhesive surface plate by injecting wax heated to ℃ from the periphery of the wafer to the center using a syringe.

Next, the concave surface of the wafer bonded to the adhesive surface plate was wrapped on one side for 30 minutes at a pressure of 10 gr/cm ² to remove any warping, and finally, the wafer, which had been heated and peeled off from the adhesive surface plate, was wrapped at a pressure of 60 gr/cm ² Both sides were simultaneously wrapped for 30 minutes to eliminate variations in the thickness of the wafers wrapped on one side.

As a result of wrapping under the above conditions, when only conventional double-sided simultaneous wrapping was used, there was no reduction in the amount of warpage of sliced wafers, but according to the present invention, the amount of warpage of sliced wafers was reduced. Regardless of the size, we were able to reduce the amount of warpage to 3 μm or less in all cases.

In the embodiment of the present invention, when single-sided wrapping is performed, the convex surface of the wafer is bonded to a surface plate and the concave surface is wrapped, but the concave surface may be bonded and the convex surface is wrapped.

In addition, as a method for bonding the wafer to the bonding surface plate without deforming the wafer, in the case of the present invention, a method was used in which wax was injected from the periphery of the wafer toward the center. You can apply an adhesive such as wax to the adhesive layer, place the wafer parallel to it, and then sink the wafer into the adhesive layer due to its own weight and fix the wafer onto the adhesive surface plate. Although wax is used as the adhesive material, a liquid or fluid adhesive that adheres by surface tension or the like may also be used.

As explained above, according to the present invention, the amount of warpage of a sliced wafer can be reduced by wrapping by first performing double-sided simultaneous wrapping, then single-sided wrapping, and finally double-sided simultaneous wrapping. Can be done.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a wafer in which both sides of the wafer are wrapped simultaneously, according to an embodiment of the present invention. Figure 2 is a cross-sectional view of the wafer shown in Figure 1, with the convex side bonded and the concave side wrapped on one side. is a cross-sectional view of the wafer peeled off from the adhesive surface plate after single-sided wrapping;
FIG. 4 is a sectional view of a wafer obtained by wrapping the wafer on both sides of the wafer shown in FIG. 3 which was wrapped on one side. In the figure, 1... wafer, 2... adhesive surface plate,
3... Adhesive layer broken line represents the shape of the wafer before single-sided wrapping.

Claims (1)

[Claims] 1. When wrapping a wafer, first wrap the wafer on both sides simultaneously, then wrap the wafer on one side to remove warpage,
A wafer wrapping method characterized by simultaneously wrapping both sides at the end.