Growth behavior of polycrystalline silicon thin films deposited by RTCVD on quartz substrates

Polycrystalline silicon (poly-Si) thin films were prepared on quartz substrates by rapid thermal chemical vapor deposition (RTCVD) system, and their structures were studied by XRD, SEM and TEM, respectively. XRD spectra exhibit a single strong (220) diffraction peak, which indicates that the poly-Si films are preferentially <110> oriented. Plane-view SEM images show that the surface of the poly-Si films is composed of large numbers of polygonal pyramid grains with different sizes, and cross-section SEM images further indicate that they are columnar grains with growth direction perpendicular to substrate surface. TEM observation results demonstrate that there are a lot of twin crystals including one-order, two-order and high-order (≥3) twin crystals in the poly-Si films. The above experimental results can not be elucidated by the conventional opinion on growth behavior of poly-Si films prepared by atmosphere pressure chemical vapor deposition (APCVD), but can be explained by the Ino’s multiply twinned particles (MTPs) model found in the face centered cubic metal films. According to the above experimental results and Ino’s model, we tend to think that nucleation and grain growth of poly-Si films deposited by RTCVD on quartz substrates are based on the formation of MTPs, and then these MTPs form the continuous films in an island growth mode.