High-density microwave plasma of SiH₄/H₂ for high rate growth of highly crystallized microcrystalline silicon films

Abstract

The plasma parameters for the fast deposition of highly crystallized microcrystalline silicon (µc-Si) films with low defect density are presented using a high-density and low-temperature SiH₄-H₂ mixture microwave plasma. A very high deposition rate of $\sim $ 65 Å/s was achieved for a SiH₄ concentration of 67% diluted in H₂ with a high Raman crystallinity I _c/I _a > 2.5 and a low defect density of 1−2 × 10¹⁶ cm⁻³ by adjusting the plasma conditions. Contrary to the case of a conventional rf plasma, the defect density of the µc-Si films strongly depends on substrate temperature, T _s, and increases with increasing T _s even if T _s is below 300 °C. This indicates that the real temperature at the growing surface is higher than the monitored value. A sufficient supply of deposition precursors such as SiH₃ at the growing surface under an appropriate ion bombardment is effective for the fast deposition of highly crystallized µc-Si films as well as for the suppression of the amorphous incubation and transition interface layers at the initial growth stage.