Thermal dissociation process of hydrogen atoms in plasma-enhanced chemical vapor deposited silicon nitride films

Annealing characteristics of plasma-enhanced chemical vapor deposited silicon nitride films have been evaluated. Annealing temperature dependence for N–hydrogen bonds decreases monotonically with increasing temperature, while that for Si–hydrogen bonds initially increases and then decreases. The annealing time dependence of the absorption coefficients indicate the N–hydrogen bonds have two bonding configurations: one dissociates from 400 °C, and the other above 600 °C. The dissociation of the weaker configuration follows the first-order reaction, and the estimated activation energy is about 0.45 eV. For the Si–hydrogen bonds, the increase of the absorption coefficient in the initial stage of annealing is due to the recombination of hydrogen released atoms from the N–hydrogen bonds with Si dangling bonds, which occurs because of the dense structures of the films. By subtracting out this increase due to the recombination reaction, it is found that the dissociation reaction for the Si–hydrogen bonds is also a first-order reaction, and the estimated activation energy is 0.60 eV.