Process Analysis and Optimization on PECVD Amorphous Silicon on Glass Substrate

In this paper, depositing of low stress Amorphous Silicon (alpha-Si) with high deposition rate by using a plasma-enhanced chemical vapour deposition (PECVD) system (STS, Multiplex Pro-CVD) was studied. The influence of the process parameters, such as power, frequency mode, argon flow rate, temperature and pressure, on these objectives have been studied and optimized. RF modes (13.56 MHz and 380 kHz) have obvious influence on the deposition rate of amorphous silicon, which revealed that high RF mode provide higher deposition rate, but not certain on the residue stress. The power has a proportional relationship to the deposition rate, and also, is proportional to stress induced at high RF mode, so low power is preferred for low stress film. At high RF mode, the deposition rate decreases with temperature while stress increases. By increasing the gas flow rate of argon, the film stress is found to decrease for both RF modes, while the deposition rate decreases for the low RF mode. Lastly, at high RF mode, pressure is also proportional to deposition rate and stress (compressive). The proper process conditions were optimized to get the low stress alpha-Si. The application of alpha-Si sacrificial layer in the glass etching process is also briefly highlighted and illustrated at the end of this paper.