Simulation of a capacitively coupled silane/hydrogen discharge

Summary form only given. Capacitively coupled SiH₄/H₂ plasmas have been widely employed for deposition of Si film for applications such as thin film transistors and thin film solar cells. For Si thin film solar cells, requirements for yielding higher conversion efficiency at a lower cost calls for a high rate and high uniformity plasma process for deposition of microcrystalline Si film. A better understanding of the plasma discharge is needed. In this study, a VHF SiH₄/H₂ CCP discharge is simulated using a commercially available fluid code, CFD-ACE+ (ESI Corp). Simulation was performed for VHF SiH₄/H₂ CCP operated at 27.12 MHz with 27 species and 47 reactions. Simulation results show that, for a power density of 0.4 W/cm², a gas pressure of 600 Pa and a SiH₄/H₂ flow rate ratio of 2.5/200, electron density profile is quite uniform in the discharge gap region with density up to 1.8×10¹⁶ 1/m³. For the key species related to the film formation, SiH₃ and H, density profile for SiH₃ is uniform in the discharge gap with a density ~8.3~10¹⁷ 1/m³, while H profile peaks near the electrode edge. More interestingly, the H density profile is strongly influenced by rf voltage temporal variation but the heavier SiH₃ profile is not sensitive to rf voltage temporal variation. The detailed simulation results of the parametric analysis by varying, e.g., rf power, gas flow rates, or gas mixtures, will be presented.