Influence of Plasma Characteristics on the Film Structure and Properties of Low Temperature PECVD Epitaxial Silicon*

The homoepitaxial growth of silicon by low temperature PECVD is particularly significant for the advancement of kerfless wafer production. The chemistry mixture ratio, flow rate, interface preparing method and rf power density have been widely studied. However, the effects of radical species concentration and other plasma parameters are less frequently discussed. In this study, we explore these relationships through a series of experimental comparisons between the plasma characteristics and the epitaxial silicon film structure and properties. The homemade PECVD system consists of a gas distribution showerhead mounted on the top lid and a grounded bottom electrode, which also functions as the substrate heater, maintained at 180℃ in this study. A 13.56 MHz rf power is coupled to the showerhead to excite the plasma. The plasma characteristics were primarily studied using optical emission spectroscopy, a compact spectrometer with an optical resolution of 0.5 nm and a wavelength range of 200-1100 nm was used to collect and analyze the light emission peaks corresponding to the relative radical species of silane/hydron plasma, particularly Si, SiH*, H_α, H_β and H₂ Fulcher.  The epitaxial silicon films were analyzed using Raman spectroscopy and the morphology and thickness were investigated by AFM and profilometry, respectively. The issue of process window drifts due to the continuous change in the chamber wall surface condition during the epitaxial growth will also be presented.