Effect of wire temperature on the microstructural evolution of Si films in hot-wire chemical vapor deposition for digital display and photovoltaic devices

The formation of crystalline phase in Si by hot-wire chemical vapor deposition (HWCVD) was investigated, focusing on the microstructural evolution as a function of hot-wire temperature. The microstructure of films deposited on a Si wafer was compared between hot-wire temperatures of 1590, 1670, and 1800 °C. A heavily twinned structure was observed at the wire temperature of 1670 °C, which resulted in the apparent intensity peak of (1 1 1) hexagonal-closed packed (HCP) crystalline Si from a typical face-centered cubic (FCC) crystalline Si structure in the X-ray diffraction analysis. The twin-related HCP crystalline phase was markedly diminished at 1800 °C and hardly observed at 1590 °C. The observed deposition behavior was approached by the effect of the wire temperature on the size of charged nanoparticles formed in the gas phase in the HWCVD process.