Optimized surface passivation of n and p type silicon wafers using hydrogenated SiNx layers

We have investigated surface passivation of n and p type silicon wafers, obtained by controlling silicon–hydrogen bonding and fixed charge densities with the use of hydrogenated SiNx films. The hydrogenated SiNx films were deposited by single PECVD at 13.56 MHz with SiH4/NH3 gas mixture. The hydrogenated SiNx films of refractive indices 2.55–1.92 and high optical band-gap (> 3.1 eV) were obtained by varying the hydrogenated SiNx film composition. The fixed charge densities, hydrogen-bonding and carrier lifetime performance in n and p type silicon wafer were analyzed. The highest fixed positive charge of 2.66 × 1012 (cm− 2) was for the hydrogenated SiNx film composition of 1.21. Fourier transform infrared spectroscopy measurement was carried out to evaluate the bonding concentration of Si–H and N–H. The minority carrier lifetimes of the hydrogenated SiNx passivated silicon wafers were up to 153 μs and 84 μs for p and n type, respectively. Mechanism of surface passivation depends on the type of silicon wafer. The higher Si–H bond density is the key point of n type passivation quality. The large fixed positive charge is used to measure p type passivation quality.