Power density in RF PECVD: a factor for deposition of amorphous silicon thin films and successive solid phase crystallization

Abstract

Solid phase crystallization of amorphous silicon thin films deposited by radio frequency plasma enhanced chemical vapour deposition (RF PECVD) has been studied. The effects of power density variation on the properties of amorphous and microcrystalline films (after crystallization) have been discussed. A fast growth rate of the amorphous layer (12.5 Ås-1) and large grain (~350Å) microcrystalline film has been reported. A high value of electrical dark conductivity (~10-6S cm-1) is also obtained for the microcrystalline (intrinsic) film. It has been observed that deposition rate and bonded hydrogen content in the amorphous films play important roles in the crystallization process and properties of the crystallized films. Electron resonance spectra indicate an increase in defect density of amorphous films with increase in power density and better crystallization is obtained for films with higher density of defects. Scanning electron microscopy reveals that the nature of film surfaces and distribution of grain in the crystallized films are strongly affected by thepower density regime in the deposition process.