Low temperature formation of microcrystalline silicon films using high-density SiH4 microwave plasma

A microwave discharge utilizing a spokewise antenna was successfully applied for high rate deposition of microcrystalline silicon (μc-Si:H) film at low substrate temperatures of 200–250°C. Systematic deposition studies were carried out with the total pressure, H2 dilution ratio and flow rate of SiH4, Fr(SiH4), as variables, combined with optical emission spectroscopy (OES) and Langmuir probe characterizations. It was revealed that the total pressure was the most important parameter for determining the deposition rate, which exhibited a maximum at 40–50 mtorr along with good crystallinity. By optimizing the plasma parameters together with the axial distribution of electron density, ne, a high deposition rate of ∼47 Å/s is achieved in the highly crystallinitzed and photoconductive μc-Si:H growth. A correlation among OES signal intensity, SiH, the intensity ratio, IHα/ISi*, deposition rate and film crystallinity is demonstrated.