A methodology for optimizing a constant temperature polysilicon deposition process

A three-step approach to characterizing a low pressure chemical vapor deposition (LPCVD) constant temperature polysilicon process is discussed. This approach optimizes an LPCVD polysilicon process for both film uniformity and particles. The first step is to design and construct a constant deposition temperature polysilicon furnace to provide the best system performance possible in terms of particle generation and improved film uniformity. The second step is to characterize a process in this newly constructed furnace for both film uniformity and particles by using an experimental design that incorporated an L₁₈ orthogonal array. The hydrogen chloride preclean flow prior to deposition plays a key role in both defect generation and film uniformity. Both capacitance-voltage techniques and secondary ion mass spectrometry are used to understand this role. The third step is to verify the recommended setting from the experimental design by processing confirmation runs. Results from the confirmation runs in the optimally constructed polysilicon furnace show that particles can be reduced by up to 66% and film uniformity can be improved by 29% over the current production process