Chemical Vapor Deposited Polycrystalline Silicon

Mirror smooth thin films of polycrystalline silicon suitable for FET device processing have been chemically vapor deposited from silane at 650°C on different insulating materials. Hall mobilities of p‐type and n‐type films have been measured for carrier concentrations between 10 14 /cc and 10 20 /cc. Unusually high mobilities, within a factor of two of bulk silicon, were obtained in the 10 14 /cc to 10 17 /cc carrier concentration range. In situ vapor doping control was irreproducible for carrier concentrations below . Evidence from radiochemical analysis, electron microscopy, and x‐ray analysis indicates that there is a large concentration of electrically inactive dopant which is postulated to be in the grain boundaries. Undoped polysilicon films could be deposited with resistivities greater than 10 6 ohm‐cm.