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Smooth Polysilicon Films Using Dichlorosilane

IP.com Disclosure Number: IPCOM000061767D
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Barbee, SG: AUTHOR [+5]

Abstract

Disclosed is a process for low pressure chemical vapor deposition (LPCVD) of polysilicon using dichlorosilane (SiH2Cl2) reactant gas in which the carrier gas and SiH2Cl2 are introduced simultaneously into the deposition system in a slow and controlled manner. LPCVD of polysilicon using SiH2Cl2 normally results in a film having a rough surface due to large irregular grains. Polysilicon base transistors made with such a film suffer from low electrical test yields. In the process, hydrogen (H2) gas is used first to pre-purge the deposition system, and then as the carrier gas for the SiH2Cl2 during the actual deposition, following which the H2 serves as a post- purge gas. The flow of the reactant gas is brought up slowly during the deposition phase without changing the H2 flow.

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Smooth Polysilicon Films Using Dichlorosilane

Disclosed is a process for low pressure chemical vapor deposition (LPCVD) of polysilicon using dichlorosilane (SiH2Cl2) reactant gas in which the carrier gas and SiH2Cl2 are introduced simultaneously into the deposition system in a slow and controlled manner. LPCVD of polysilicon using SiH2Cl2 normally results in a film having a rough surface due to large irregular grains. Polysilicon base transistors made with such a film suffer from low electrical test yields. In the process, hydrogen (H2) gas is used first to pre-purge the deposition system, and then as the carrier gas for the SiH2Cl2 during the actual deposition, following which the H2 serves as a post- purge gas. The flow of the reactant gas is brought up slowly during the deposition phase without changing the H2 flow. Polysilicon films deposited in this manner are quite dull or hazy as observed in the photograph of Fig. 1A. This dull or hazy appearance is caused by significant light-scattering due to large grain asperities on the surface (Fig. 2A). In the present process, the H2 pre-purge is used, but the gas flow is reduced at the end of the pre-purge step to only about 5% of set- point during deposition. For polysilicon deposition, the H2 and the SiH2Cl2 are introduced simultaneously and their flows brought up together until the set-point is reached. At the conclusion of the deposition, the SiH2Cl2 is turned-off and the hydrogen continued for a post-purge step...