Effects of discharge parameters on deposition rate of hydrogenated amorphous silicon for solar cells from pure SiH4 plasma

A systematic deposition of hydrogenated amorphous silicon films from pure SiH4 plasma was made in a capacitively coupled rf glow-discharge system by changing anode–cathode spacing d and chamber pressure p simultaneously. The data of the deposition rate in the p-vs-d space had two boundaries. One was pd=const. The other seems to be pd2=const. The rf plasma can stably sustain between the boundaries. The boundaries are discussed with rf power per SiH4 molecule and with overlapping Paschen’s lines of various fragments, especially H2 due to the SiH4 dissociation. We found the optimum conditions in which the deposition rate was more than 10 Å/s without large photo-induced degradation. 10% efficient p-i-n solar cells were achieved with the intrinsic layer deposition rate of 3.9 Å/s and more than 6% efficiency with 10 Å/s.