藤浪 眞紀

SiO₂ films (thickness : 500 nm) deposited on Si(100) by plasma- and thermal-assisted chemical vapor deposition (CVD) using tetraethylorthosilicate (TEOS) were studied by Fourier transform infrared spectroscopy (FTIR), etch rate, and variable-energy positron annihilation spectroscopy. As the substrate temperature at deposition was raised, the density of the SiO₂ films increased and the Si-OH impurity content decreased. On the other hand, Si-OH impurities in the SiO₂ films could not be removed even at a substrate temperature of 440°C The Si-OH content in plasma-assisted CVD SiO₂ films was much lower than that in thermal-assisted CVD SiO₂ films at the same substrate temperature. It was found from FTIR and the positron study that the water tended to exist as Si-OH clusters, whose surroundings had more open space than those of normally bonded O₃≡Si-O-Si≡O₃.

The defect profile induced by F ion implantation (120 keV, 2×10¹⁴/cm²) into a Czochralski (Cz)-Si wafer was determined by analysis using a slow positron beam method. It was proved that vacancies were present at ppm concentrations at depths exceeding 1.5μm, far beyond the depth to which F ions were implanted. The induced defects consisted of at least two components which could be correlated with their depth.: Annealing at 300°C extinguished the defects only in the deeper region and annealing at 600°C extinguished those in the ion implanted region. It was, further, confirmed that the use of an improved Monte-Carlo-deduced positron implantation profile was better than that of the Gaussian derivative one in calculating defect profiles.