Guiding Principles for Obtaining High-Quality Microcrystalline Silicon at High Growth Rates Using SiH₄/H₂ Glow-Discharge Plasma

We present guiding principles for preparing high-quality microcrystalline silicon (μc-Si:H) with regard to film precursors and to their reactions on film-growing surfaces, in which, apart from the temperature, the contributions of short-lifetime reactive species to film growth are the determining factors of the defect density of the resulting films. The importance of the scavenging reactions of short-lifetime species by SiH₄ as well as that of their low generation rate is emphasized. The necessity of considering the coexisting annihilation reactions of atomic hydrogen, which is an essential species for μc-Si:H formation, is indicated. On the basis of these guiding principles, we propose a high-rate deposition technique using plasma-enhanced chemical vapor deposition with a newly designed interconnected multihollow cathode. Spatially resolved optical-emission spectroscopy indicates a radical separation effect introduced by the cathode. Device-grade μc-Si:H films with low defect densities (∼5 × 10¹⁵ cm^-3) are successfully deposited at rates approaching 8nm/s using this technique.