Large-area polycrystalline p-type silicon films produced by the hot wire technique

The role of the deposition pressure and hydrogen dilution in the production of p-type Si:H films by hot wire chemical vapor deposition, was investigated. The system used permits to obtain uniform and homogenous films properties over a 10cmx10cm substrate area. As heated filament we used Ta, since Ta filaments have longer fife period without deteriorating than the W filaments ones. In this work, we show that the electrical properties of the films produced are dependent on the process gas pressure. In the pressure range of 13.3Pa (0.1 Torr) to 66.5 Pa (0.5Torr), the film's coplanar electrical conductivity at room temperature varies by more than two orders of magnitude, for films produced at same hydrogen dilution and filament temperature, reaching values of about 0.1 (Omega cm)(-1), at deposition pressures of about 40-53Pa (0.3-0.4Torr). On the other hand, the increase in hydrogen dilution (from 87% to 96%) promotes the surface roughness due to an enlargement of grain sizes in the direction of the {220} diffraction planes as observed by SEM micrographs without changing the crystalline fraction (48-50%) obtained by micro-Raman analysis.