| AVS 60th International Symposium and Exhibition | |
| Plasma Science and Technology | Tuesday Sessions |
| Session PS-TuP |
| Session: | Plasma Science and Technology Poster Session |
| Presenter: | H.B. Lin, National Tsing Hua University, Taiwan, Republic of China |
| Authors: | H.B. Lin, National Tsing Hua University, Taiwan, Republic of China S.E. Lien, National Tsing Hua University, Taiwan, Republic of China C.H. Hsieh, National Tsing Hua University, Taiwan, Republic of China K.C. Leou, National Tsing Hua University, Taiwan, Republic of China C.C. Hsieh, Institute of Nuclear Energy Research, Taiwan, Republic of China C.F. Ai, Institute of Nuclear Energy Research, Taiwan, Republic of China |
| Correspondent: | Click to Email |
Capacitively coupled SiH4/H2 plasmas (CCP) have been widely employed for depostion 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 porcess for deposition of microcrystalline silicon (m-Si) film. A better understanding of the plasma discharge is needed. In this study, a 80 MHz SiH4/H2 CCP discharge has been investigated by numerical simulation based on fluid model, with 27 species and 47 reactions. Simulation results show that plasma density, as well as the number densities and fluxes of H, SiH2, and SiH3, important reactive species for the growth of m-Si film, as well as the ratio of H/SiH3 flux, a key indicator for crystal fraction of m-Si film, increase with rf power, as expected. Compared with the case in 27.12 MHz, the results also show that plasma density for the 80 MHz discharge are higher, due to frequency effect in the dominate electron heating mechanism, and, consequently, the densities of the key radical species also drop. More importantly, the ratio of of H/SiH3 flux is also higher for the 80 MHz cases. Further more, the plasma potential, which determines the energy of ions incident on the grounded substrate electrode, decreases as operation frequency decreases. Consequently, a higher crystal fraction can be obtained by increasing the frequency of the rf power of plasma reactors, due to less damage on films causes energy ions bombardment. Simulations have also been carried out for different gap spacing between two electrodes and calculation results show that plasma density increases as the gap spacing decreases, as a result of lower electric field strength.
*Work supported by the National Science Council of ROC.