Effect of annealing ambient on the precipitation processes in oxygen-implanted silicon on-insulator material
In the last decade, oxygen implanted silicon-on-insulator material (SIMOX: Separation by IMplantation of OXygen) has been extensively studied, due to its potential advantages of increased speed and radiation hardness in integrated circuits. SIMOX material requires two processing steps: first, implantation of a high dose of oxygen to form a buried oxide layer below a thin, top silicon layer; second, a high temperature anneal in an inert gas atmosphere to remove implantation damage and oxide precipitates. Most earlier studies investigated the effect of annealing temperature and time, but did not consider the effect of gas ambient. The effect of nitrogen and argon on the oxide-precipitate formation in bulk silicon has been established. Raider et al. found that in annealing of bulk silicon, nitrogen can diffuse to an oxide-silicon interface and chemically react with silicon. The nitrogen-containing layer acts as a barrier to further oxidation. Consequently, nitrogen influences the growth kinetics of the thermal oxide while annealing in an argon ambient does not. This should apply to SIMOX as well. We have, therefore, investigated the effect of nitrogen and argon ambient on the oxide-precipitate removal during annealing of SIMOX material.