Deposition of HWCVD poly-Si films at a high growth rate

Abstract

The process parameters for high growth rate poly-silicon films by hot-wire chemical vapour deposition have been explored. A four-wire hot wire assembly has been employed for this purpose. High silane to hydrogen flow ratios and high wire temperatures are the key process parameters to achieve high growth rate and growth rates higher than 5 nm/s can be achieved. The process conditions to incorporate high hydrogen content into the material for passivation of defects and donor states have been identified as high hydrogen dilution and lower wire temperature. With these procedures poly-Si films deposited at 1.3 nm/s showed high ambipolar diffusion length of 132 nm. Incorporating such poly-Si films as i-layer, n–i–p solar cell on stainless steel substrate without back reflector showed an efficiency of 4.4%.