High-quality amorphous silicon thin films for tunnel oxide passivating contacts deposited at over 150 nm/min

摘要

Hot-wire chemical vapor deposition was utilized to develop rapidly grown and high-quality phosphorus-doped amorphous silicon (a-Si:H) thin films for poly-crystalline silicon on tunnel oxide carrier-selective passivating contacts. Deposition rates higher than 150 nm/min were obtained for the in situ phosphorus-doped a-Si:H layers. To optimize the passivating contact performance, material properties such as microstructures as well as hydrogen content were characterized and analyzed for these phosphorus-doped a-Si:H films. The results show that a certain microstructure of the films is crucial for the passivation quality and the conductance of passivating contacts. Porous silicon layers were severely oxidized during high-temperature crystallization, giving rise to very low conductance. The insufficient effective doping concentration in these layers also yields inferior passivation quality due to lack of field-effect passivation. On the other hand, dense silicon layers are insensitive to oxidation but very sensitive to blistering of the films during the subsequent high-temperature process steps. By optimizing the deposition parameters, a firing-stable-implied open-circuit voltage of 737 mV and a contact resistivity of 10 m omega center dot cm(2)were achieved at a high deposition rate of 100 nm/min while 733 mV and 90 m omega center dot cm(2)were achieved at an even higher deposition rate of 150 nm/min.