In situ study on the growth of microcrystalline silicon film using the high-density microwave plasma for Si thin film solar cells

摘要

Growth processes of microcrystalline silicon (μc-Si) has been investigated on ZnO:Al/Ag by utilizing the high-density microwave plasma-enhanced chemical vapor deposition of a SiH_4-and-H_2 mixture at different deposition rate conditions of 2-3 and 20 A/s. In situ spectroscopic ellipsometry and Fourier-transform infrared reflection absorption spectroscopy (FTIR-RAS) studies revealed that there exists an induction time at which the nucleation starts at a low deposition rate of 2-3 A/s, similar to that of the conventional rf plasma. The deposition proceeds and is accompanied by the relaxation of the Si network during the film growth. On the other hand, the deposition proceeds with any induction time at a high deposition rate of 20 A/s along with the formation of intermixing layer of ZnO:Al and the deposition of Si of ～ 500 A thickness. The structural relaxation of Si network is also still promoted with a long time constant even after the plasma excitation is turned off.