Properties of polycrystalline silicon films prepared from fluorinated precursors

Polycrystalline silicon films have been prepared at low temperature on glass substrate from fluorinated precursors by PECVD technique varying the hydrogen dilution and gas flow rate. Undoped film with dark-conductivity 1.05×10⁻² S cm⁻¹ has been obtained. For n-type poly-Si film the highest conductivity achieved is 2.8 S cm⁻¹. Grain size observed from SEM varies from 4 to 6 μm for undoped and 2 to 3 μm for phosphorous doped films. The main crystalline peak is 〈111〉 whereas the crystallite size calculated from XRD is 350 Å. The optical absorptions and hydrogen contents in the films deposited under different conditions have been studied. Growth kinetics are dominated by the precursors SiF_nH_m (m+n≤3) and concentrations of F and H on the growth surface.