NH3 Plasma Interface Modification for Silicon Surface Passivation at Very Low Temperature

概要

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The effect of passivation layers (SiOX, SiNX, etc.) using plasma-enhanced chemical vapor deposition (PECVD) for crystalline silicon solar cells showed high surface recombination with decreasing of deposition temperature (${<}300$ °C). The surface of Czochralski (Cz) monocrystalline silicon (c-Si) wafer was exposed to an NH3 plasma before the low-temperature deposition of silicon nitride (SiNX) layer or amorphous silicon (a-Si:H) layer in a system respectively. The effect of NH3 plasma treatment for the interface was observed by microwave photoconductance decay (μ-PCD), quasi-steady-state photoconductance (QSSPC), Fourier transform infrared spectroscopy (FT-IR), secondary ion-microprobe mass spectrometry (SIMS), and X-ray photoemission spectroscopy (XPS). The effective lifetime ($\tau_{\text{eff}}$) with NH3 plasma treatment exceeded $\tau_{\text{eff}}$ without the treatment. Even in the case of very low deposition temperature (100 °C), $\tau_{\text{eff}}$ is improved dramatically (about 38 times). This NH3 plasma treatment effect was caused by hydrogenation and carbon cleaning from the SIMS measurement. It was found that SiNX films with excellent surface passivation properties can be deposited at 100 °C.
2008-07-25