Cylindrical Sleeve Technique for Improved Single Wafer Uniformity in LPCVD Processes
Original Publication Date: 1984-Feb-01
Included in the Prior Art Database: 2005-Feb-02
Low pressure chemical vapor deposition (LPCVD) processes accomplish large batch size depositions by closely packing wafers such that they approximate an annular cylinder in the reaction tube. For many processes, this configuration is adequate for uniform film thicknesses across each wafer. However, certain reactions result in severe radial thickness nonuniformities across the wafers. This has been attributed to inter-wafer radial diffusion-caused reactant depletion. Examples of such processes are: 1. Arsenic or phosphorous, in-situ doped polysilicon using SiH4 with AsH3 or PH3; 2. Si3N4 by SiH4/NH3; 3. SiO2 by SiH4/O2; and 4. Phosphosilicate glass or arsenosilicate glass by SiH4/O2/PH3 or AsH3; tetraethoxysilane TEOS/PH3 or AsH3.