Nucleation study of hydrogenated microcrystalline silicon (μc-Si:H) films deposited by VHF-ICP

Nucleation in the initial stage of hydrogenated microcrystalline silicon (μc-Si:H) film deposition by VHF inductivity-coupled plasma (ICP) has been investigated. When the SiH4 concentration (RSiH4 = [SiH4] / ([SiH4] + [H2])) is 6%, the crystallization in the initial 1.1-2.4 nm film deposition is observed at the substrate temperature of 320 °C, while it is decreased to 150 °C by reducing the RSiH4 to 3%. Furthermore, the nucleation is significantly promoted by H2 plasma pretreatment as long as 90 s prior to μc-Si:H film deposition. The crystallinity was improved from 33 to 54% and the grain density was increased from 8.0 × 1010 to 1.7 × 1011 cm− 2 by the pretreatment. We confirmed no significant change in SiO2 surface micro roughness after the H2 plasma pretreatment. The chemical bond states at the SiO2 surface before film deposition play an important role in nucleation.