Evolution of a-Si:H to nc-Si:H transition of hydrogenated silicon films deposited by trichlorosilane using principle component analysis of optical emission spectroscopy

Plasma Enhanced Chemical Vapor Deposition (PECVD) has been used for direct production of wafer-equivalent quality silicon thin film solar cells, includes the nc-Si:H deposition film. In this paper, the nano-crystalline silicon thin films were deposited on Si substrate by PECVD from source gas of trichlorosilane (TCS, SiHCl₃) at temperatures 400 °C. The in-situ plasma monitoring and the resultant deposited film properties of the a-Si:H to nc-Si:H transition (ANT) were characterized by Optical emission spectroscopy (OES), Fourier transfer infrared spectroscopy (FTIR), Raman spectroscopy (RS), Scanning Electron Microscope (SEM) and Alpha-Step profiler. In addition, principal component analysis (PCA) based on large scale OES dataset was performed and the value of crystalline phase (VCP) was established to differentially characterize the nanocrystalline phase as mean VCP of 0.11 and the control limits of 0.06, which can be used as the in-situ monitoring tool for crystalline phase characterization. Through the proposed PC1-DEV algorithm, the high-dimensional OES data of complexity should be selected and reduced to radicals of interest (SiCl*, SiCl2*, Hα and H_β) to make a decision with strong classifier performance.