EFFECTS OF RAPID THERMAL ANNEAL ON REFRACTIVE-INDEX AND HYDROGEN CONTENT OF PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITED SILICON-NITRIDE FILMS

The objective of this paper is to understand and quantify the effects of rapid thermal anneal (RTA) on refractive index, thickness, and hydr ogen content of plasma-enhanced, chemical vapor-deposited (PECVD) sili con nitride films. It is shown that RTA is more effective than identic al furnace anneal. A threshold in as-deposited refractive index value is found, above which the index of a silicon nitride film increases, w hile the thickness and bonded hydrogen content decreases as result of the RTA. In addition, the magnitude of increase in the index is propor tional to the as-deposited index value. The threshold index value incr eases with the increase in silicon nitride deposition temperature. A d irect correlation is found between the annealing-induced increase in r efractive index and the corresponding decrease in total bonded hydroge n concentration in the PECVD silicon nitride films. Finally, it is sho wn that the release of bonded hydrogen from the film can passivate def ects in the underlying silicon substrate and increase the performance of silicon devices such as solar cells. (C) 1996 American Institute of Physics.