Nitric acid oxidation of Si method at 120 °C: HNO3 concentration dependence

Electrical characteristics and physical properties of 8-10 nm silicon dioxide (SiO2) films formed on Si (100) substrates by use of the nitric acid oxidation of Si method at similar to 120 degrees C have been investigated. The atomic density of the SiO2 layer increases with the HNO3 concentration. Fourier transformed infrared absorption measurements show that the higher the HNO3 concentration, the higher the atomic density of the SiO2 layer. From the Fowler-Nordheim plots, the barrier height at the SiO2/Si interface is found to increase with the HNO3 concentration. The leakage current density flowing through the SiO2 layer decreases with the HNO3 concentration employed for the SiO2 formation. It is concluded that the higher atomic density leads to SiO2 band-gap widening and thus to the higher band discontinuity energy at the SiO2/Si interface, which in turn results in a decrease in the tunneling probability of charge carries through SiO2. The density of oxide fixed charges decreases with an increase in the HNO3 concentration. When postmetallization annealing is performed at 250 degrees C in hydrogen atmosphere on the SiO2 layer formed with 68 wt % HNO3, electrical characteristics become as good as those of a thermally grown SiO2 layer formed at 900 degrees C. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3296395]