Film thickness reduction of thermally annealed hydrogenated amorphous silicon prepared with plasma-enhanced chemical vapor deposition

Abstract

The structural change of thermally annealed hydrogenated amorphous silicon films prepared with plasma-enhanced chemical vapor deposition has been examined in this study. At 615 °C, a significant amount of microvoids can be annealed out of the silicon films. The annihilation of microvoids mainly causes the reduction of film thickness while the surface smoothness is largely retained. During annealing, the thickness of silicon films has been reduced by 220 Å from the initial thickness of 1200 Å. Evaluated with the thickness reduction alone, the void fraction of the as-deposited films must be higher than 16%. The film thickness reduction starts at the very early stage of annealing and has almost completed within 30 min. Our results also have shown that the reduction of film thickness cannot be the result of crystallization, instead, it is more likely accompanied with the hydrogen effusion.