Effective Interface Modification by NH_3 Plasma for Silicon Surface Passivation at Very Low Temperatures

摘要

The p-type Czochralski (Cz) Si material was exposed to an NH_3 plasma before the low temperature deposition of silicon nitride (SiN) or silicon oxide (SiO) layer in a Plasma-Enhanced Chemical Vapor Deposition (PECVD) system. The effect of this NH_3 plasma-treatment for the interface was observed by means of Microwave Photo Conductance Decay (μ-PCD), Quasi-Steady-State PhotoConductance (QSSPC), Fourier Transform InfraRed spectroscopy (FT-IR) and Secondary Ion-microprobe Mass Spectrometer (SIMS). The effective lifetime with NH_3 plasma-treatment exceeded the effective lifetime without the treatment. Even in the case of the very low deposition temperature (100℃), the effective lifetime was improved dramatically (about 38 times). And the mechanism of NH_3 plasma-treatment is the effect of hydrogenation and carbon cleaning from the result of SIMS measurement. It was found that SiN films with excellent surface passivation properties can be deposited at 100℃. In the results of NH_3 plasma-treatment, the outstanding surface passivation of high efficiency thin silicon solar cells will be obtained using SiN films deposited at very low temperature (100℃).