Low-temperature growth of crystalline silicon on a chlorine-terminated surface

Abstract

We report on the role of surface termination during growth of crystalline silicon at low temperatures. Microcrystalline silicon was fabricated using plasma-enhanced chemical-vapor deposition with a hydrogen-diluted dichlorosilane (SiH2Cl2)/monosilane (SiH4) mixture to study the role of hydrogen and chlorine in crystal formation. When varying the fraction of SiH2Cl2, x=[SiH2Cl2]/([SiH4]+[SiH2Cl2]), good crystallinity was obtained for x=0 and 1, whereas the crystallinity was markedly deteriorated for intermediate x. Optical emission spectroscopy of the plasma suggests that film precursors different from SiHx fragments and atomic chlorine are generated for x≠0 and that atomic hydrogen is generated in all cases. Infrared reflection absorption spectroscopy indicates that the surface coverage is hydrogen for x=0, chlorine for x=1, and a hydrogen–chlorine mixture for intermediate x. These results imply that low-temperature growth of crystalline silicon is facilitated on a chlorine-terminated surface as well as on a hydrogen-terminated surface under the presence of atomic hydrogen. The cooperative roles of chlorine and hydrogen are proposed in the crystal growth of Si.