Low temperature fabrication of 5-10 nm SiO2/Si structure using advanced nitric acid oxidation of silicon (NAOS) method

We have developed the advanced nitric acid oxidation of Si (NAOS) method to form relatively thick (5-10 nm) SiO2/Si structure with good electrical characteristics. This method simply involves immersion of Si in 68 wt% nitric acid aqueous solutions at 120 deg. C with polysilazane films. Fourier transform infrared absorption (FT-IR) measurements show that the atomic density of the NAOS SiO2 layer is considerably high even without post-oxidation anneal (POA), i.e., 2.28 x 1022 atoms/cm2, and it increases by POA at 400 deg. C in wet-oxygen (2.32 x 1022 atoms/cm2) or dry-oxygen (2.30 x 1022 atoms/cm2). The leakage current density is considerably low (e.g., 10-5 A/cm2 at 8 MV/cm) and it is greatly decreased (10-8 A/cm2 at 8 MV/cm) by POA at 400 deg. C in wet-oxygen. POA in wet-oxygen increases the atomic density of the SiO2 layer, and decreases the density of oxide fixed positive charges.