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Method for Producing Biconcave Wafers

IP.com Disclosure Number: IPCOM000047062D
Original Publication Date: 1983-Sep-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Zebrowski, A: AUTHOR [+2]

Abstract

The barrel etcher is used to remove the damage caused by lapping. After this step, the wafers are polished. Unfortunately, double-side polishing, which is currently used as a standard, degrades the wafer geometry so that the wafers become biconvex. The objective of the present method is to produce biconcave wafers at the barrel-etching operation in order to compensate for the above-mentioned effect, and thus to obtain semiconductor wafers with improved flatness. A first solution might consist in increasing the distance between the spacers; however, this technique drastically reduces productivity. The proposed method consists in using the standard barrel etcher but with special spacers provided with four holes arranged in such a way that they roughly correspond to the center of the wafers (see the figure).

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Method for Producing Biconcave Wafers

The barrel etcher is used to remove the damage caused by lapping. After this step, the wafers are polished. Unfortunately, double-side polishing, which is currently used as a standard, degrades the wafer geometry so that the wafers become biconvex. The objective of the present method is to produce biconcave wafers at the barrel-etching operation in order to compensate for the above- mentioned effect, and thus to obtain semiconductor wafers with improved flatness. A first solution might consist in increasing the distance between the spacers; however, this technique drastically reduces productivity. The proposed method consists in using the standard barrel etcher but with special spacers provided with four holes arranged in such a way that they roughly correspond to the center of the wafers (see the figure). These holes produce extra acid exchange between the spacers and consequently accelerate the removal of the silicon material at the center of the wafer. The wafers are introduced between the spacers as usual, and the barrel is submerged in a special acid bath, such as 8- 3-1 (8 volumes of HNO3, 3 volumes of CH3 COOH4, 1 volume of HF). Reproducible and controlled wafer geometry is obtained after the barrel etcher step. This ultimately results in super-flat wafers after the polishing step, without any reduction in productivity.

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