Formation of Si:H:Cl Films at Low Temperatures of 90–140°C by RF Plasma-Enhanced Chemical Vapor Deposition of a SiH2Cl2 and H2 Mixture

Abstract

The role of chlorine in the formation of chlorinated hydrogenated silicon (Si:H:Cl) films is investigated through film depositions at low temperatures of 90–140°C by rf (13.56 MHz) plasma-enhanced chemical vapor deposition (PE-CVD) of a dichlorosilane SiH2Cl2 and H2 mixture. There exists the threshold substrate temperature of ∼110°C for phase transition from polysilane/siloxene to nanocrystalline Si (nc-Si), which is ruled by the chemical reactivity of the deposition precursor, SiHxCly (x+y<3) on the growing surface. The Si:H:Cl films deposited at substrate temperature Ts below 110°C have polysilane/siloxene structure and they show relatively strong photoluminesence in the visible region of 600–800 nm. On the other hand, most of the chlorine atoms are consumed to release the hydrogen from the growing surface at Ts above 110°C, resulting in the nc-Si formation. This difference is determined by the surface reaction during film growth.