EQUILIBRATION IN AMORPHOUS-SILICON NITRIDE ALLOYS

Several series of amorphous silicon nitride films have been grown over a wide range of deposition temperatures. Photothermal deflection spec troscopy measurements showed that the defect density N-D is determined by the Urbach slope, E(0), for most of these samples, suggesting that defect equilibration occurs in a-SiNx:H for values of x up to at leas t 0.6. The growth temperature at which the disorder is minimised incre ases with increasing x, which is explained in terms of a hydrogen-medi ated bond equilibration reaction. Fourier transform infra-red spectros copy revealed changes in hydrogen bonding with growth temperature whic h suggest that a second bond equilibration reaction also occurs at the growing surface, but that equilibrium cannot be reached at higher tem peratures because of hydrogen evolution from Si-H bonds.