Analysis of flatband voltage shift of metal/high-k/SiO₂/Si stack based on energy band alignment of entire gate stack

A theoretical model of flatband voltage (V_FB) of metal/high-k/SiO₂/Si stack is proposed based on band alignment of entire gate stack, i.e., the V_FB is obtained by simultaneously considering band alignments of metal/high-k, high-k/SiO₂ and SiO₂/Si interfaces, and their interactions. Then the V_FB of TiN/HfO₂/SiO₂/Si stack is experimentally obtained and theoretically investigated by this model. The theoretical calculations are in good agreement with the experimental results. Furthermore, both positive V_FB shift of TiN/HfO₂/SiO₂/Si stack and Fermi level pinning are successfully interpreted and attributed to the dielectric contact induced gap states at TiN/HfO₂ and HfO₂/SiO₂ interfaces.