Abstract
In this thesis, the effects of process pressure, plasma power, hydrogen flow rate, silane flow rate and temperature on the growth of three kinds of silicon thin film, i.e. intrinsic microcrystalline, p-type and n-type silicon thin film via very-high-frequency PECVD (VHF-PECVD) were systematically discussed. Moreover, various electrical and structural properties such as deposition rate, crystallinity, grain size, energy band gap, conductivity, doping concentration and diffusion length were investigated thoroughly for the application of silicon thin film solar cells. On the basis of literature, the deposition rate and crystallization are important factors to affect the performance of silicon thin film. Hence, these two parameters provide a starting-point in our study. The largest deposition rate was found to be a process pressure of 4 torr, plasma power of 400W, hydrogen flow rate of 600sccm, temperature of 200℃ and silane flow rate of 40sccm. Moreover, the best crystallization was found to be a process pressure of 7torr, plasma power of 300W, hydrogen flow rate of 1000sccm, temperature of 200℃ and silane flow rate of 30sccm. Energy band gap could be varied from 1.4eV to 2.0eV under different environment. The transportation of carriers between intrinsic microcrystalline silicon thin film and solar cell electrode is better for the higher electrical conductivity to generate large photo-current. The highest electrical conductivity was observed to be a process pressure of 2 torr, plasma power of 300W, hydrogen flow rate of 400sccm, temperature of 300℃ and silane flow rate of 15sccm. The optimum behavior was performed in a process pressure of 4 torr, plasma power at 300W, hydrogen flow rate of 600sccm, temperature of 200℃, silane flow rate of 15sccm.