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Method for Sputter Cleaning of Polysilicon

IP.com Disclosure Number: IPCOM000050292D
Original Publication Date: 1982-Oct-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Campbell, DR: AUTHOR [+2]

Abstract

An intermittent sputter-etching method is provided for cleaning polysilicon films and particularly for removing native oxide from the surface of the polysilicon films, on which silicide is to be deposited to form silicide-polysilicon double layers as conductive structures in FET and bipolar devices. The native oxide, if present, forms an effective diffusion barrier preventing the migration of silicon across the silicide-silicon interface. Removal of the native oxide is essential for satisfactory adhesion of co-deposited silicide films.

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Method for Sputter Cleaning of Polysilicon

An intermittent sputter-etching method is provided for cleaning polysilicon films and particularly for removing native oxide from the surface of the polysilicon films, on which silicide is to be deposited to form silicide-polysilicon double layers as conductive structures in FET and bipolar devices. The native oxide, if present, forms an effective diffusion barrier preventing the migration of silicon across the silicide-silicon interface. Removal of the native oxide is essential for satisfactory adhesion of co-deposited silicide films.

An effective method for removal of native oxide from single crystal silicon is continuous sputter etching with argon gas. The sheet resistance and adhesion of WSi(2)/P/-/ Si structures improves with the duration of sputter etching. In contrast, extending the time of sputter etching of N polysilicon films ultimately degrades adhesion. This is ascribed to heating of the polysilicon layer and subsequent grain boundary reaction "in situ" to regrow a barrier layer.

This problem is avoided by a new sputter-etching method wherein the total desired time of sputter etching of from 6 to 14 minutes at 500 watts applied power and 7 motor argon pressure, is divided into short increments of from 1 to 4 minutes, in between which the plasma is extinguished for a set time of from 1 to 15 minutes to allow the polysilicon films to cool. This limits the total temperature excursion of the polysilicon surface a...