Hydrogen as the cause of pit-formation during laser recrystallization of silicon on insulator films

Summary form only given. An extensive study of the ability of CVD-materials to induce the formation of pits has been carried out. The results of the study show that most of the CVD materials used in IC processing can induce the formation of pits in the recrystallized SOI film. The formation of pits is correlated with the hydrogen content of the capping layer; if no hydrogen is present in the capping layer, no pits are formed. The pits are the result of the formation of hydrogen gas bubbles in the molten silicon zone. The mechanism of pit formation consists of: decomposition of hydrogen bonds in the capping layer, dissolving of hydrogen in the molten zone, precipitation of hydrogen near the solidification interface and freeze-in of the gas bubbles. Based on this mechanism, the dependency of the pit formation on capping layer composition and thickness, on the recrystallization conditions and on the silicon film thickness can be explained. The change of the appearance of the pits with scan velocity and their typical droplet-like shape can also be explained by the presented mechanism