SIMS study on N diffusion in hafnium oxynitride

Abstract As the MOS device feature size continues to shrink, novel high- k gate dielectrics should be adopted to reduce the unacceptable high gate leakage current due to direct tunneling. HfO 2 is one of the most promising high- k materials. It was reported that HfN x O y formed by incorporating N into HfO 2 could improve the thermal stability and electrical properties of the gate dielectric films. However, N loss can occur due to subsequent high temperature processes, such as rapid thermal processing (RTP). It is necessary to understand the mechanism of N loss from the academic and application points of view. In this study, SIMS was applied to investigate the N diffusion behavior in sputter-deposited HfN x O y after RTP processing. The results showed that N loss is due to out-diffusion of N to the surface. On the other hand, segregation of N at the interface of HfN x O y /Si was observed. N acts as a good barrier to O diffusion from HfN x O y to Si. The results show that oxygen flooding is unfavorable for characterizing N in HfN x O y /Si since oxygen flooding can enhance the N background.