Highly concentrated ͑Ͼ93 vol %͒ ozone (O 3) gas was used to oxidize silicon for obtaining high-quality SiO 2 film at low temperature. Compared to O 2 oxidation, more than 500°C lower temperature oxidation ͑i.e., from 830 to 330°C͒ has been enabled for achieving the same SiO 2 growth rate. A 6 nm SiO 2 film, for example, could be grown at 600°C within 3 min at 900 Pa O 3 atmosphere. The temperature dependence of the oxidation rate is relatively low, giving an activation energy for the parabolic rate constant of 0.32 eV. Furthermore, a 400°C grown SiO 2 film was found to have satisfactory electrical properties with a small interface trap density (5ϫ10 10 cm Ϫ2 /eV) and large breakdown field ͑14 MV/cm͒.
An ultra low-temperature (< 300°C) silicon oxidation process in which KrF excimer laser light (λ=248 nm) is irradiated in highly concentrated ozone has been developed. The growth rate of SiO2 film was 5.2 nm/10 min at 300°C and 3.6 nm/10 min at 70°C. The leakage current densities of grown at 70°C SiO2 in an electric field of over 8 MV/cm match well the calculated curve based on the Fowler–Nordheim tunneling. The oxidation mechanisms for two growth modes are discussed.
Charge density waves (CDW) in a tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) single crystal have been studied with molecular resolution using a low temperature scanning tunneling microscope (STM). For the first time the periodicities of the CDW along both the a and b axes have been observed and were found to be coincident with those of the 2k F CDW. The influence of crystal singularities on the ordering of the CDW along the a axis was also revealed. [S0031-9007(98)
We have grown SiO 2 films on polycrystalline Si using excited ozone produced by ultraviolet light irradiation of ozone, and characterized their electrical properties in the metal-insulator-semiconductor capacitor configuration. SiO 2 films of ϳ8.5 nm thickness on poly-Si layers were grown in 60 min even at room temperature. The leakage current density across the SiO 2 film fitted well the Fowler-Nordheim tunnel current behavior and breakdown occurred at above 12 MV/cm, showing that the film was of device quality. The rate of Si oxidation by excited ozone was similar for both Si͑100͒ and Si͑111͒ wafers, as was the interface trap density ͑D it ͒. These results indicate that excited ozone can form a homogenous SiO 2 film on poly-silicon. We conclude that excited ozone is one of the most efficient reactive species for SiO 2 film formation on poly-Si at room temperature.
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