Low temperature formation of SiO2∕Si structure by nitric acid vapor

Abstract

Si can be oxidized at temperatures between 350 and 500°C by use of nitric acid (HNO3) vapor, resulting in 5–10nm SiO2∕Si structure. The oxidation kinetics follows a parabolic law, indicating that diffusion of oxidizing species (i.e., oxygen atoms generated by decomposition of HNO3 molecules) through SiO2 is the rate-determining step. The leakage current density flowing through the SiO2 layer formed at 350°C follows the Poole-Frenkel mechanism, indicating the presence of trap states in the SiO2 band gap, and the trap energy is estimated to be 0.57eV below the SiO2 conduction band. On the other hand, the leakage current density for the SiO2 layer formed at 500°C follows the Fowler-Nordheim mechanism, showing the absence of trap states.