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The influence of vessel-wall temperature T w on the grain size of poly-Si films deposited on a low-temperature (300°C) substrate by an inductively-coupled SiH4/H2 plasma is investigated. The grain size is reduced after a clean vessel wall at T w ∼100°C experiences long SiH4/H2 discharge. This reduction in the grain size due to SiH4/H2 discharge duration can be suppressed by heating the wall to T w ∼300°C. To understand the mechanism, the H atom density in the plasma is measured from the ratio of Hα/Hβ emission intensities. The H atom density is found to decrease monotonically with the discharge time at T w ∼100°C, and this H density decrease is suppressed by increasing the wall temperature to ∼300°C.

An inductively coupled plasma (ICP) is successfully modified to deposit polycrystalline silicon (poly-Si) films on a glass substrate (4 diluted by hydrogen. The modification includes a gas residence time control and a dielectric cover on an internal metal antenna. A metal antenna discharge in 2% SiH4 at a total pressure of 2.0 Pa results in a monotonically increasing deposition rate up to 0.4 nm/s with a decrease in the residence time to 18 ms. The dielectric-covered antenna makes the deposition rate two times higher than the metal antenna. The higher crystallinity of the deposited film is achieved with a lower residence time and/or a smaller percentage of SiH4, both of which decrease the deposition rate. For example, a 600W 0.3% SiH4 discharge by the dielectric cover antenna gives a poly-Si grain size of 140 nm from the X-ray diffraction (XRD) spectra and a crystallization factor of 0.98 from the Raman spectra.