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LPCVD of Polysilicon by Hydrogen Reduction of Dichlorosilane

IP.com Disclosure Number: IPCOM000041537D
Original Publication Date: 1984-Feb-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Barbee, SG: AUTHOR

Abstract

The standard process for polysilicon by low pressure chemical vapor deposition (LPCVD) uses 100% silane flowing at approximately 100 standard cubic centimeters per minute into a chamber at 625ŒC with an inlet pressure of from 0.100 torr to 0.500 torr. To get uniform-thickness coatings on single wafers that are stacked closely to one another, pressures on the order of one one-thousandth of atmospheric pressure is necessary. A uniform-thickness polysilicon film may be deposited with a reasonable growth rate and at only one twentieth of atmospheric pressure while using close wafer spacing in the deposition reactor. However, instead of using silane, dichlorosilane is used as the silicon source gas. In addition, hydrogen is used to reduce the dichlorosilane to silicon and hydrogen chloride gas.

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LPCVD of Polysilicon by Hydrogen Reduction of Dichlorosilane

The standard process for polysilicon by low pressure chemical vapor deposition (LPCVD) uses 100% silane flowing at approximately 100 standard cubic centimeters per minute into a chamber at 625OEC with an inlet pressure of from
0.100 torr to 0.500 torr. To get uniform-thickness coatings on single wafers that are stacked closely to one another, pressures on the order of one one- thousandth of atmospheric pressure is necessary. A uniform-thickness polysilicon film may be deposited with a reasonable growth rate and at only one twentieth of atmospheric pressure while using close wafer spacing in the deposition reactor. However, instead of using silane, dichlorosilane is used as the silicon source gas. In addition, hydrogen is used to reduce the dichlorosilane to silicon and hydrogen chloride gas. Typical conditions used are as follows:

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The reactor uses a conventional, approximately 40 cubic feet per minute rotary vane pump. After initial loading of the wafers and pumpdown, the wafers are "soaked" in H2 for 15 minutes to thermally equilibrate prior to deposition. A growth rate of 60 A/min was obtained for an average thickness of 3030 A polysilicon across twenty wafers. The overall thickness uniformity (based on 3 monitor wafers - 5 readings per wafer: four at the edge, one at the center) was
1.4%. A larger batch size will result in uniformity degradation to some extent.

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