SiO₂ films deposited at low temperature by using APCVD with TEOS/O₃ for TFT applications

A silicon-dioxide (SiO₂) film was deposited using tetra ethyl orthosilicate (TEOS) along with oxygen (O₂) or ozone (O₃) as a reaction gas in an atmospheric pressure chemical vapor deposition (APCVD) system instead of using a hazardous gas like SiH₄. It was impossible to grow the film below 500 °C by using O₂ as a reaction gas. The films deposited at 400 °C using O₃ as a reaction gas showed the best deposition rate and electrical and optical properties good enough to make them applicable for many semiconductor devices, especially poly-silicon (poly-Si) thin-film transistors (TFTs). The annealing of the films at 700 °C was found to reduce the interface defect density, making the film more useful as a passivation layer. Conventional APCVD requires high-temperature processing whereas in the current study, we developed a low-temperature process. The interface trap density was substantially decreased in the silicon surface coated with the silicon dioxide film after annealing in an air ambient.