Nitric acid oxidation of silicon at ∼120 °C to form 3.5-nm SiO2/Si structure with good electrical characteristics

3.5-nm-thick SiO2 layers can be formed at 120 degreesC by immersion of Si in 40 wt % nitric acid (HNO3) followed by immersion in an azeotropic mixture (i.e., 68 wt % HNO3). The former immersion produces a 1.1-nm SiO2 layer with a low atomic density of 2.19x10(22)/cm(2), where the layer acts as a catalyst for the decomposition of HNO3. The latter immersion results in a 3.5-nm SiO2 layer with a higher atomic density of 2.22x10(22)/cm(2). When the postmetalization annealing treatment at 250 degreesC in hydrogen is performed on the <Al/3.5-nm SiO2/Si(100)> metal-oxide semiconductor diodes, interface states are passivated and a low leakage current density (e.g., 8x10(-4) A/cm(2) at the forward gate bias of 1.5 V) is achieved. (C) 2004 American Institute of Physics.