Wire-desorbed radicals present during hot-wire chemical vapor deposition growth have been measured by quadrupole mass spectrometry. New wires produce Si as the predominant radical for temperatures above 1500 K, with a minor contribution from SiH 3 , consistent with previous measurements; the activation energy for the SiH 3 signal suggests its formation is catalyzed. Aged wires also produce Si as the predominant radical ͑above 2100 K͒, but show profoundly different radical desorption kinetics. In particular, the Si signal exhibits a high temperature activation energy consistent with evaporation from liquid silicon. The relative abundance of the other SiH x species suggests that heterogeneous pyrolysis of SiH 4 on the wire may be occurring to some extent. Chemical analysis of aged wires by Auger electron spectroscopy suggests that the aging process is related to the formation of a silicide at the surface, with silicon surface concentrations as high as 15 at. %. A limited amount ͑2 at. %͒ of silicon is observed in the interior as well, suggesting that diffusion into the wire occurs. Calculation of the relative rates for the various wire kinetic processes, coupled with experimental observations, reveals that silicon diffusion through the silicide is the slowest process, followed by Si evaporation, with SiH 4 decomposition being the fastest.

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Wire-desorbed radicals present during hot-wire chemical vapor deposition growth have been measured by quadrupole mass spectrometry. For wire temperatures in excess of 1500 K, Si is the predominant radical desorbed from a new wire, with a minor contribution from SiH3. Aged wires showed profoundly different radical desorption kinetics, consistent with evaporation of Si from liquid silicon. It is proposed that this aging is related to silicide formation at the surface of the wire.

One- and two-dimensional numerical simulations have been used to determine the parameters critical to high rate growth of high quality polycrystalline silicon via hot-wire chemical vapor deposition at silane partial pressures of 1-70 mTorr and a wire temperature of 2000°C. The Direct Simulation Monte Carlo method [1] was used, including gas-phase chemistry relevant for growth. Model predictions agree both qualitatively and quantitatively with experimental measurements.

We apply a rate-equation pair binding model of nucleation kinetics [1] to the nucleation of Si islands grown by hot-wire chemical vapor deposition on SiO2 substrates. Previously, we had demonstrated an increase in grain size of polycrystalline Si films with H2 dilution from 40 nm using 100 mTorr of 1% SiH4 in He to 85 nm with the addition of 20 mTorr H2. [2] This increase in grain size is attributed to atomic H etching of Si monomers rather than stable Si clusters during the early stages of nucleation, decreasing the nucleation density. Atomic force microscopy (AFM) measurements show that the nucleation density increases sublinearly with time at low coverage, implying a fast nucleation rate until a critical density is reached, after which grain growth begins. The nucleation density decreases with increasing H2 dilution (H2:SiH4), which is an effect of the etching mechanism, and with increasing temperature, due to enhanced Si monomer diffusivity on SiO2. From temperature-dependent measurements, we estimate the activation energy for surface diffusion of Si monomers on SiO2 to be 0.47 ± 0.09 eV. Simulations of the temperature-dependent supercritical cluster density lead to an estimated activation energy of 0.42 eV ± 0.01 eV and a surface diffusion coefficient prefactor of 0.1 ± 0.03 cm2/s. H2-dilution-dependent simulations of the supercritical cluster density show an approximately linear relationship between the H2 dilution and the etch rate of clusters.