DSMC - simulation of the influence of hydrogen addition on the properties of silicon deposited by HWCVD

The gas phase chemistry in a hot-wire chemical vapor deposition (HWCVD) process, which utilizes an array of heated tungsten wires is analyzed via Direct Simulation Monte Carlo simulation. Process gases are silane (SiH4) and hydrogen (H2). SixHy radical partial pressures are simulated as a function of H2 gas flow for given gas inlet compositions in order to optimize radical partial pressures, leading to higher quality and more ordered Si:H films. The simulation results are compared with a series of deposition runs using an array of 10 heated tungsten wires (600 mm long, 0.53 mm diameter, held at 2100 °C) providing a deposition area of 500 x 600 mm². H2 gas flows are varied to maximize the crystallinity of Si:H films as measured through Raman spectroscopy. The experimental sets are further compared to the simulation results by means of in-situ mass spectrometry, film thickness measurement, and process pressure measurement.