Structural and electrical analysis of silicon thin films deposited by transformer-coupled-plasma chemical-vapor deposition

In this study, silicon thin films were deposited by using a transformer-coupled-plasma chemical-vapor deposition (TCPCVD) technique using SiH ₄/H ₂/PH ₃, and the effects of rf power on the structural and the electrical properties of the deposited thin films were investigated for applications to silicon solar cells. Increasing the rf power from 50 to 500 W increased the percent of crystalline silicon in the film from 42 to about 79 %. The increase in crystalline silicon was mostly attributed to an increase in the number of nanosized crystalline silicon grains having grain sizes from 3 to 15 nm. The increase in crystalline percent was also accompanied by an increase in the stress in the film. The increased crystalline silicon percent in the films increased the dark conductivity and, at 500 W of rf power, a dark conductivity of 10 Ω ^-1cm ^-1 could be obtained for a 40-nm-thick film, which is applicable to silicon-based solar cells.