Study of hydrogenated silicon thin film deposited by using dual-frequency inductively-coupled plasma-enhanced chemical-vapor deposition

Abstract

Microcrystalline silicon thin films were deposited using an inductively-coupled plasma source with an internal linear-type antenna in the dual frequency mode (2 MHz/13.56 MHz), and the characteristics of the thin film and the plasma were investigated as functions of the relative power ratio. The deposition was performed in the SiH4 depletion condition at a deposition rate of about 10 A/s to improve the microstructural properties of the film. In the dual-frequency mode, the crystalline volume fraction could be increased by increasing the low-frequency power, which is added to the fixed 13.56 MHz rf power without changing the microstructure factor (R*), which is related to defects in the crystal structure. The differences appear to be related to the lower-energy ion bombardment of the substrate in the dual-frequency mode. In addition, by increasing the low-frequency power from 0 to 1.5 kW while keeping 3 kW at 13.56 MHz, we were able to change the uniformity of the deposition from 15.5% to less than 10% an improvement.