Smooth Polysilicon Films Using Dichlorosilane
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
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.