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

The role of chlorine in the formation of chlorinated hydrogenated silicon (Si:H:Cl) films is investigated through film depositions at low temperatures of 90-140degreesC by rf (13.56 MHz) plasma-enhanced chemical vapor deposition (PE-CVD) of a dichlorosilane SiH2Cl2 and H-2 mixture. There exists the threshold substrate temperature of similar to110degreesC 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 T-s below 110degreesC 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 110degreesC, resulting in the nc-Si formation. This difference is determined by the surface reaction during film growth.