The low-temperature growth of epitaxial Si films by atmospheric pressure plasma chemical vapor deposition (AP-PCVD) was investigated. A 150 MHz very high frequency (VHF) power supply was used to generate an atmospheric pressure plasma of gas mixtures containing He, H 2 , and SiH 4 . Two types of electrode (i.e., cylindrical rotary and porous carbon electrodes) were used in plasma generation. When a cylindrical rotary electrode was used, polycrystalline Si growth was inevitable at the film edge on the upstream side. This is due to the variation in deposition rate along the gas flow direction, which is extremely high at the plasma/atmosphere interface on the upstream side. To solve this problem, we developed a novel porous carbon electrode where process gas molecules are directly supplied into the plasma region through a porous carbon plate a distance (0.8 mm) away from the substrate surface. Using such a porous carbon electrode, we successfully grew a defect-free epitaxial Si film on the entire surface of a 4 in. Si wafer at 600 C. The average growth rate was 0.25 -0.3 mm/min, which is as high as that obtained by thermal CVD at 900 C. The epitaxial Si films grown at 600 C were characterized by various methods, including transmission electron microscopy, atomic force microscopy, secondary ion mass spectrometry, and selective etching. The influence of adsorbed impurities in the porous carbon material on the quality of epitaxial Si films was also investigated.

High-quality epitaxial Si films have been grown at low temperatures (500 -600 C) by atmospheric pressure plasma chemical vapor deposition (AP-PCVD) with a high growth rate (0.31 mm/min at 600 C averaged over the 4-in. wafer). In contrast to the previous reports on other low-temperature CVD Si, the films in the present study are defect-free as observed by transmission electron microscopy and selective etching, and show no oxygen and carbon pileups at the film/substrate interface. To characterize defect-free epitaxial films with high sensitivity, we employed a photoluminescence (PL) method. When the epitaxial layer has better quality than the substrate, PL spectrum at 4.2 K mainly reveals the property of the substrate. On the other hand, room temperature PL measurements clearly show that the PL intensities of the surface-passivated epitaxial Si samples are much higher than that of Czochralski (CZ)-Si, which indicates a longer minority carrier recombination lifetime in the epitaxial Si layer than the bulk lifetime in CZ-Si.

No abstract