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

Abstract

Vibrational properties of hydrogenated silicon-rich nitride ( S i N 𝑥 : H ) of various stoichiometry ( 0 . 6 ≤ 𝑥 ≤ 1 . 3 ) and hydrogenated amorphous silicon ( a - S i : H ) films were studied using Raman spectroscopy and Fourier transform infrared spectroscopy. Furnace annealing during 5 hours in Ar ambient at 1 1 3 0 ∘ 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 - S i : 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.