Effect of N 2O/SiH 4 flow ratios on properties of amorphous silicon oxide thin films deposited by inductively-coupled plasma chemical vapor deposition with application to silicon surface passivation

Abstract

Silicon oxide (SiO x) thin films have been deposited at a substrate temperature of 300 °C by inductively-coupled plasma chemical vapor deposition (ICP-CVD) using N 2O/SiH 4 plasma. The effect of N 2O/SiH 4 flow ratios on SiO x film properties and silicon surface passivation were investigated. Initially, the deposition rate increased up to the N 2O/SiH 4 flow ratio of 2/1, and then decreased with the further increase in N 2O/SiH 4 flow ratio. Silicon oxide films with refractive indices of 1.47–2.64 and high optical band-gap values (>3.3 eV) were obtained by varying the nitrous oxide to silane gas ratios. The measured density of the interface states for films was found to have minimum value of 4.3 × 10 11 eV −1 cm −2. The simultaneous highest τ eff and lowest density of interface states indicated that the formation of hydrogen bonds at the SiO x/c-Si interface played an important role in surface passivation of p-type silicon.