Analysis of hafnium and nitrogen interstitial defects at Si-oxynitride interfaces

Oxynitride films have been identified as potential high-k dielectrics in high-k/Si interfaces or as an interlayer film in high-k gate stacks, demonstrating a number of advantages. The processing however, of gate stack materials consisting of nitrogen or hafnium atoms often results in the formation of defects in the dielectric that degrade the performance of the device. In this paper, four different interface models for crystalline oxynitride on (001)Si substrate are investigated upon their properties in the presence of interstitial nitrogen and hafnium defects. The four defect-free models of the oxynitride film on Si substrate, form state-free insulating interfaces and each of the models is subsequently compared to the respective model with nitrogen and hafnium-based defects at various locations along the cell in the oxynitride bulk or in the silicon bulk. The analysis shows that hafnium defects are clearly energetically favorable at the Si-oxynitride interface, while nitrogen is more likely to form a defect at the oxynitride bulk than at the silicon substrate.