Hydrogenated amorphous silicon: Hydrogen content, bonding configurations and morphology in sputter-deposited, in-chamber annealed thin films

Abstract

The infrared absorption features of sputter-deposited amorphous silicon (a-Si:H) thin films prepared under different substrate temperatures ( T s) and an in-chamber annealing treatment were analysed as a function of anneling temperatures ranging from 200 to 600°C. Fourier-transform infrared absorption spectroscopy and scanning electron microscopy were used to analyse the evolution of film characteristics after annealing. Hydrogen bonding configurations for higher T s, in-chamber annealed samples showed a higher proportion of monohydride grouping, and further annealing steps revealed that hydrogen is much more tightly bonded under these deposition conditions than when T s is lower and the in-chamber annealing treatment not used. Oxygen and nitrogen contamination, both during and after deposition, have also been found to be reduced when samples were in-chamber annealed. Samples deposited at low T s and not in-chamber annealed showed the same surface damage as samples prepared at higher T s and which were then annealed at temperatures starting at 300°C, indicating a high degree of stress, probably caused by an excessive hydrogen concentration in films prepared at lower T s.