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System Gettering by Polysilicon Scavengers

IP.com Disclosure Number: IPCOM000086866D
Original Publication Date: 1976-Nov-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Kemlage, BM: AUTHOR [+4]

Abstract

A polysilicon film on the back of the substrate will result in a limited amount of metallic impurities, originally residing in the substrate or the environment, to be gettered to the backside polysilicon layer. However, if a large amount of impurities is encountered, the polysilicon film on the substrate back becomes saturated and cannot handle the residual impurities. When this structure is inserted into an epitaxial system or a chemical vapor deposition (CVD) system, where large amounts of impurities are encountered, the polysilicon gettering film on the substrate back will immediately upon heating become saturated and the residual impurities have no other place but the active device regions in the single crystalline substrate to locate, thus resulting in as poor or poorer yields than the nonpolysilicon sample.

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System Gettering by Polysilicon Scavengers

A polysilicon film on the back of the substrate will result in a limited amount of metallic impurities, originally residing in the substrate or the environment, to be gettered to the backside polysilicon layer. However, if a large amount of impurities is encountered, the polysilicon film on the substrate back becomes saturated and cannot handle the residual impurities. When this structure is inserted into an epitaxial system or a chemical vapor deposition (CVD) system, where large amounts of impurities are encountered, the polysilicon gettering film on the substrate back will immediately upon heating become saturated and the residual impurities have no other place but the active device regions in the single crystalline substrate to locate, thus resulting in as poor or poorer yields than the nonpolysilicon sample.

A technique which will eliminate or, at least, greatly reduce this problem is that polycrystalline silicon slabs are prepared to serve as scavengers for the large flux of impurities introduced by the epitaxial system, CVD system, gases, etc. Pure polysilicon ingots can easily be cut to the desired configuration which would be to overlap the monocrystalline substrate.

Impurities would now prefer to reside at the polysilicon, rather than the single crystalline silicon, substrate. Also, by direct contact of the substrate to the polycrystalline slab, impurities in the substrate could be pulled out into the scavenger...