Polycrystalline Silicon Technology For VLSI Applications

The technology of polycrystalline silicon (polySi) deposition is traced from its introduction in the 1960's to the modern, low-pressure chemical vapor deposition (LPCVD) process that has become commercially viable for high-throughput,, low-cost VLSI circuit manufacture. The advantages of LPCVD of polySi by the pyrolytic decomposition of silane are discussed, and the dependence upon deposition parameters, such as temperature, pressure, and the effects of specific dopants, are described. The conditions that lead to amorphous, fine-grained polycrystalline, or columnar polycrystalline structure are defined. Methods for controlling the resistivity by diffusion, ion implantation or in-situ doping are presented.