The plasma diagnosis by optical emission spectroscopy for the study of phosphorus doped nanocrystalline silicone film growth

Phosphorus doped nanocrystalline silicon (nc-Si) that deposited on a p-type silicon substrate was prepared by standard radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD). The optical emission spectroscopy (OES) is used as a diagnostic tool for analyzing the processing species and intensity in plasma. The obtained SiH∗ spectra are recorded to explain results from the deposition rate of nanocrystalline silicon. The deposition rate increases with increasing power when the electrode distance, working pressure and total flow rate are fixed. Moreover, we also describe ratios of Hα∗ / SiH∗ and Si∗ / SiH∗ to represent the crystallization rate index and electron temperature respectively. Based on OES results, we can utilize plasma spectra as database to monitor film properties. The spectroscopic ellipsometer (SE) and hall measurements were used to further study the growth rate, crystallinity, and electrical property of the films. Under the process conditions of 225°C substrate temperature, 11mW/cm2 power density, 300mTorr working pressure and 30mm electrode distance, the best optimized n-type nc-Si films on a 4cm2 bifacial p-type Cz silicon wafer were obtained.