Formation of SiO2/Si structure with low interface state density by atmospheric-pressure VHF plasma oxidation

SiO2/Si structure has been prepared by atmospheric-pressure (AP) plasma oxidation at 400 °C using gas mixtures of 0.5–5% O2 and He. From the characterization results of thickness, refractive index, atomic composition and electrical properties of the oxide films, it is found that the properties of SiO2/Si structures formed by AP-plasma oxidation are similar to those of high-temperature grown thermal oxides. By optimizing formation conditions, the SiO2/Si structure with a low interface state density of 1.4 × 1010 cm−2 eV−1 is obtained. On the other hand, the positive fixed charge density in the AP-plasma oxide film is relatively high at 5.3 × 1011 cm−2. These characteristics (low interface state density and high fixed charge density) are useful for effective field-effect passivation of Si surfaces for photovoltaic application.