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Etching the Rim of Si Wafers

IP.com Disclosure Number: IPCOM000083734D
Original Publication Date: 1975-Jul-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Briska, M: AUTHOR

Abstract

During the grinding of grown silicon crystals, prior to slicing them into wafers, crystal defects occur which may reach depths of about 100 microns. These defects existing on the wafer rims after slicing, spread during subsequent heat treatment steps. Therefore, the wafer rim area containing the defects is removed by etching.

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Etching the Rim of Si Wafers

During the grinding of grown silicon crystals, prior to slicing them into wafers, crystal defects occur which may reach depths of about 100 microns. These defects existing on the wafer rims after slicing, spread during subsequent heat treatment steps. Therefore, the wafer rim area containing the defects is removed by etching.

The figure shows a simple, rapid and reproducible etching method which permits the use of an aggressive high-speed etchant, without damaging the inner surface of the wafers.

A great number of SiO(2) covered Si wafers are placed one on top of the other to form a stack 1, with the notches overlapping each other. The top and the bottom of the stack 1 are covered with bare Si wafers 2. This stack 1 is placed horizontally on a base 3 in a plastic beaker 4. HF as an etchant 5 covers the bottom of the beaker 4. The SiO(2) on the rim of the wafers is uniformly etched from the vapor phase, without the inner intermediate areas of the wafers being attacked. The etching time determines the width of the rim from which the SiO(2) is removed.

In a subsequent etching process, the bared silicon and thus the rim of the wafer containing the crystal defects is etched by a selective etchant.

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