Vibrational Spectroscopy of Chemical Species in Silicon and Silicon-Rich Nitride Thin Films

Vibrational properties of hydrogenated silicon-rich nitride (SiNx: H) of various stoichiometry (0.6 < x < 1.3) and hydrogenated amorphous silicon (a-Si: H) films were studied using Raman spectroscopy and Fourier transform infrared spectroscopy. Furnace annealing during 5 hours in Ar ambient at 1130 degrees C and pulse laser annealing were applied to modify the structure of films. Surprisingly, after annealing with such high-thermal budget, according to the FTIR data, the nearly stoichiometric silicon nitride film contains hydrogen in the form of Si-H bonds. From analysis of the FTIR data of the Si-N bond vibrations, one can conclude that silicon nitride is partly crystallized. According to the Raman data a-Si: H films with hydrogen concentration 15% and lower contain mainly Si-H chemical species, and films with hydrogen concentration 30-35% contain mainly Si-H-2 chemical species. Nanosecond pulse laser treatments lead to crystallization of the films and its dehydrogenization.