Thermal stabilization of device quality films deposited at low temperatures

The effects of postdeposition furnace annealing, at temperatures typical of metal–oxide semiconductor (MOS) fabrication processes, on gate oxides formed by remote plasma‐enhanced chemical vapor deposition (remote PECVD) are discussed. SiO₂ films were prepared by (1) remote PECVD at substrate temperatures of 200 and 400 °C, and (2) by thermal oxidation of silicon at temperatures from 850 to 1150 °C. Postdeposition thermal processing was carried out in industrial‐type diffusion furnaces in both N₂/O₂ and N₂/H₂ ambients over a temperature range of 400–1050 °C. Film properties were studied by infrared spectroscopy, ellipsometry, and by measurements of capacitance voltage (C–V) characteristics in MOS device structures. Postdeposition thermal processing at temperatures of 400 °C and above was shown to modify both the structure and electrical properties of deposited SiO₂ films. It is shown that changes in the as‐deposited film properties occur by two different relaxation mechanisms, one of which is operative in the temperature range up to 750 °C and the other from 750 to 1050 °C, and both of which are different from the viscoelastic relaxation process observed in thermally grown SiO₂.