Effects of showerhead hole structure on the deposition of hydrogenated microcrystalline silicon thin films by vhf PECVD

Abstract

The authors present the characteristics of hydrogenated microcrystalline silicon (μc-Si:H) thin films deposited from an SiH4/H2 in 40 MHz plasma enhanced chemical vapor deposition system equipped with a multihole-array showerhead. The effects of a hole-array structure are analyzed in terms of deposition rate, crystallinity, and electrical conductivity of the μc-Si:H film. The effects of process parameters, such as SiH4 concentration, radio frequency power, and total gas flow rate are also investigated. The deposition rate of a multihole-array electrode is generally lower compared with that of the flat electrode. However, a higher deposition rate is found in the deep and dense hole region when the hole shape and density are varied on the electrode. The crystallinity and conductivity are almost not affected by hole dimension and density. It is demonstrated that the multihole-array electrode can be a useful tool for uniformity improvement in a large-sized very high frequency capacitively couple plasma μc-Si:H deposition system.