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

摘要

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 τeff 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.