Extraction of Kinetic Parameters for the Chemical Vapor Deposition of Polycrystalline Silicon at Medium and Low Pressures

Abstract

The deposition of silicon (Si) from silane was studied in the silane pressure range from 0.5 to 100 Pa (0.005 to 1 mbar) and total pressure range from 10 to 1000 Pa using or He as carrier gases. The two reaction paths, namely, heterogeneous and homogeneous decomposition could be separated by varying the amount of wafer area per unit volume (wafer‐distance variation) and the partial pressure as well as the total pressure. Rate constants were derived by fitting the experimental results. The heterogeneous reaction path could be described by only the adsorption rate constants of reactive species and the desorption rate constant of hydrogen using a Langmuir‐Hinshelwood mechanism. Hydrogen and phosphine were found to suppress the deposition rate at low silane pressures. At high silane pressures or high total pressures the unimolecular decomposition of silane dominates. The unimolecular rate constant was found to be one to two orders larger than literature values based on RRKM analyses of high pressure rate data. The relative efficiency of and collisions compared with collisions in the unimolecular gas‐phase decomposition of has been investigated. Helium was found to be a weak collider compared to silane and nitrogen.