Effect of PECVD SiN_x/SiO_y N_x –Si interface property on surface passivation of silicon wafer

It is studied in this paper that the electrical characteristics of the interface between SiO_y N_x/SiN_x stack and silicon wafer affect silicon surface passivation. The effects of precursor flow ratio and deposition temperature of the SiO_y N_x layer on interface parameters, such as interface state density Di_t and fixed charge Q_f, and the surface passivation quality of silicon are observed. Capacitance–voltage measurements reveal that inserting a thin SiO_y N_x layer between the SiN_x and the silicon wafer can suppress Q _f in the film and D_it at the interface. The positive Q _f and D _it and a high surface recombination velocity in stacks are observed to increase with the introduced oxygen and minimal hydrogen in the SiO_y N_x film increasing. Prepared by deposition at a low temperature and a low ratio of N₂O/SiH₄ flow rate, the SiO_y N_x/SiN_x stacks result in a low effective surface recombination velocity (S_eff) of 6 cm/s on a p-type 1 Ω·cm–5 Ω·cm FZ silicon wafer. The positive relationship between S_eff and D_it suggests that the saturation of the interface defect is the main passivation mechanism although the field-effect passivation provided by the fixed charges also make a contribution to it. (paper)