Bonds and Defects in Plasma-Deposited Silicon Nitride Using SiH4-NH3-Ar Mixture

The compositions, structures and defects in silicon nitride films are investigated by chemical analyses, infrared absorption, electron spin resonance and breakdown strength. Even in N-rich silicon nitride, N-N bonds are hardly formed; this is in contrast with Si-Si bond formation in Si-rich films. High-temperature annealing causes a degradation of the breakdown strength for N-rich and Si-rich films, but has little effect on stoichiometric and slightly Si-rich films. Little correlation has been found between the degradation of the breakdown strength and ESR active Si dangling bonds. To explain these results, a defect model proposed by Robertson and Powell is applied to Si- and N-rich silicon nitride as well as to a stoichiometric film.