Effects of rapid thermal annealing on LPCVD silicon nitride

The effects of rapid thermal anneal (RTA) on film thickness, refractive index and residual stress of low pressure chemical vapor deposited (LPCVD) silicon nitride films are experimentally investigated. With the increase of RTA time, film thickness decreases in an exponential way and refractive index increases. Both film thickness and refractive index reach a relatively stable value after 10 min RTA process and higher RTA temperature leads to larger reduction in film thickness. Residual stress of Si-Si3N4 system monotonically increases with RTA time. Based on Maxwell viscoelastic model, a model which considers film densification and viscous flow simultaneously is obtained to quantitatively calculate the effect of RTA on residual stress. In the 900 °C and 1000 °C RTA process, film densification is dominated in the 60 min RTA process and both the mechanisms are more active with the increase of annealing temperature.