Silicon nitride deposited by ECR–CVD at room temperature for LOCOS isolation technology

For LOCOS application, silicon nitride (SiNx) insulators have been deposited by ECR–CVD at room temperature and with N2 flows of 2.5, 5, 10 and 20 sccm on pad-SiO2/Si or on Si substrates. The obtained SiNx/Si structures were used to analyze the SiNx characteristics. FTIR analyses reveal the presence of SiN and NH bonds. The refractive indexes between 1.88 and 2.48 and the thickness between 120 and 139 nm were determined by ellipsometry. With these thickness values, the deposition rates of 9.6–10.1 nm/min and the BHF etch rates of 2–86 nm/min were determined. On the SiNx/pad-SiO2/Si structures, the LOCOS process was performed. Optical and SEM microscopy analyses were used to investigate the SiNx resistance to thermal oxidation, made at 1000 °C, and the bird’s beak in the obtained LOCOS structures, respectively. These analyses reveal that SiNx insulator performed with N2 flows higher than 2.5 sccm presented high quality to LOCOS isolation technology.