The diffusion behavior was investigated by using a spun-on doped silica film. Diffusion annealing was carried out, at temperatures which ranged from 650 to 800C, using a SiO2 or Si3N4 cap. At higher temperatures, the sample surface after diffusion was found to be damaged. The profiles which were obtained at temperatures ranging from 700 to 780C were of abrupt or kink-and-tail type. Diffusion annealing which was carried out using a nitride cap were termed Ga-rich, and produced abrupt box-like profiles. The use of an oxide cap was expected to produce a superposition of shallow As-rich and deeper Ga-rich profiles; leading to a characteristic kink-and-tail profile. This behavior was observed at higher temperatures, but the junctions were too shallow to exhibit a tail at lower temperatures. The junction depths were attributed to the existence of differing activation energies for the 2 types of cap material. The energy that was required for oxide-cap diffusion was close to published values for oxide caps. The lower values which were found for nitride-cap diffusion were closer to published values for a phosphosilicate glass cap. These results clearly showed that the nature of the cap material determined the type of diffusion profile.

S.Chatterjee, K.N.Bhat, P.R.S.Rao: Solid-State Electronics, 1997, 41[3], 496-500