Effects of H₂ and Ar flow rates on the deposition of hydrogenated silicon thin films by an inductive coupled plasma-chemical vapor deposition system

Amorphous hydrogenated silicon films were deposited on quartz substrates in an inductive coupled plasma-chemical vapor deposition system with four internal low inductance antennas units. Different Ar and hydrogen flow rates were tested for their influences on the structures of deposited films. For monitoring purposes, Langmuir probe and optical emission spectrometer were installed to detect the variation of electrical field in plasma during deposition. Data from Langmuir probe and optical emission spectrometer were analyzed subsequently. After deposition, the films were examined by X-ray diffraction and Raman spectrometer for their microstructures. Results indicate that under the supply of pure Ar flow, the deposition rate can be expedited to 3.5 nm/s and amorphous films were formed on quartz substrates. With the supply of mixed hydrogen and argon (Ar 15 sccm + H₂ 50 sccm + SiH₄ 50 sccm), the deposition rate can reach 4.5 nm/s. Although it is well known that a high supply of H₂ helps the formation of micro-crystalline silicon, these deposited hydrogenated Si films, confirmed by X-ray diffraction patterns and Raman spectroscopy, all maintained their amorphousness under various range of Ar and H₂ flow rates.