Initial growth of polycrystalline silicon films on substrates subjected to different plasma treatments

Undoped 0.2-mu m-thick polycrystalline Si (poly-Si) films were deposited on fused quartz substrates by plasma-enhanced chemical vapor deposition from a SiH4-H-2 mixture. All films were prepared under the same deposition conditions,just after the substrates were exposed for 1 min to CF4-He plasma excited with various rf powers. Poly-Si films with improved crystallinity and large grains were obtained when the films were deposited on substrates with the proper degree of surface roughness of uniform size and shape. These films were also found to have lower values of stress and higher values of g, as compared with those of poly-Si films on substrates with a flat surface or an extremely rough surface. The X-ray diffraction (XRD) spectra exhibited only the [110] texture, and the intensity was proportional to the third power of the average grain size estimated from the width values of the XRD spectra. These results suggested that the growth of grains is three-dimensionally controlled and depends on the surface morphology of the substrates, while the concentration of grains per unit area is roughly independent of the morphology of the substrates.