Extended phase diagrams for guiding plasma-enhanced chemical vapor deposition of silicon thin films for photovoltaics applications

Abstract

Real time spectroscopic ellipsometry has been applied to develop extended phase diagrams that can guide the deposition of hydrogenated silicon (Si:H) thin films for highest performance solar cells. Previous such studies have shown that optimization of amorphous Si:H intrinsic layers by rf plasma-enhanced chemical vapor deposition (PECVD) is achieved using the maximum possible H2 dilution of SiH4 while avoiding a transition to the mixed-phase (amorphous+microcrystalline) growth regime. In this study, we propose that optimization of amorphous Si:H in higher rate rf PECVD processes further requires the largest possible thickness onset for a surface roughening transition detected in the amorphous film growth regime.