In this paper, we optimized the process conditions that led to nanocrystalline silicon (nc-Si:H) growth of doped silicon films as a back surface field (BSF) layer in a symmetric cell structure were prepared by standard radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD) in terms of the phosphorus flow (0∼7840ppm) and substrate temperature (125-225°C) using a (PH3/SiH4/H2/Ar) mixture. High quality of BSF layer on surface passivation was obtained after enough pre-deposition time at low electron temperature. The life time up to 1.5ms and concentrations > 1019 in 4cm2 cells can be obtained. The plasma diagnostics related to nc-Si:H solar cell deposition process was performed simultaneously during the nc-Si:H solar cell deposition process using an optical emission spectrometer (OES) to observe the stability of the chamber condition. The spectroscopic ellipsometer (SE) and hall measurements were used to study their correlations with growth rate and microstructure of the film.