Polycrystalline silicon thin films by rapid thermal chemical vapor deposition (RTCVD) on graphite substrates

Abstract

For the first time poly-silicon thin film layers have been grown on graphite substrates in an atmospheric pressure RTCVD reactor. The experiments were conducted in a temperature range from 900/spl deg/C to 1300/spl deg/C employing trichlorosilane (TCS) and the dopant trichloroborine (TCB) diluted in hydrogen. The deposited layers were evaluated by Nomarski microscopy, Rutherford backscattering spectroscopy (RBS), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The effect of deposition temperature on the growth characteristics and structure of the deposit has been studied. The grain size of the polycrystalline Si becomes coarser when the temperature is increased. The preferred orientation of the deposited Si layers changes from (222) to (311) and (220) at elevated growth temperatures. For the observed growth decline at higher precursor concentration in hydrogen we propose that the responsible mechanisms are due to thermal etching in diffusion layer and the supersaturation of silicon.