Low temperature fabrication of 5–10 nm SiO 2/Si structure using advanced nitric acid oxidation of silicon (NAOS) method

Abstract

We have developed the advanced nitric acid oxidation of Si (NAOS) method to form relatively thick (5–10 nm) SiO 2/Si structure with good electrical characteristics. This method simply involves immersion of Si in 68 wt% nitric acid aqueous solutions at 120 °C with polysilazane films. Fourier transform infrared absorption (FT-IR) measurements show that the atomic density of the NAOS SiO 2 layer is considerably high even without post-oxidation anneal (POA), i.e., 2.28 × 10 22 atoms/cm 2, and it increases by POA at 400 °C in wet-oxygen (2.32 × 10 22 atoms/cm 2) or dry-oxygen (2.30 × 10 22 atoms/cm 2). The leakage current density is considerably low (e.g., 10 −5 A/cm 2 at 8 MV/cm) and it is greatly decreased (10 −8 A/cm 2 at 8 MV/cm) by POA at 400 °C in wet-oxygen. POA in wet-oxygen increases the atomic density of the SiO 2 layer, and decreases the density of oxide fixed positive charges.