Characterization of metal/high-k structures using monoenergetic positron beams

The impact of TiN deposition on thin high-k (HfO₂ and HfSiON) films formed on Si substrates was studied using monoenergetic positron beams. For the predeposition sample, the positrons implanted into Si diffuse toward the high-k/Si interface under the influence of the electric field, suggesting the presence of negative charges in the high-k films. After TiN was deposited on HfO₂, positive charges were introduced at the TiN/HfO₂ interface, which were associated with the incorporation of nitride into HfO ₂, resulting in the formation of positively charged oxygen vacancies (V_os). From the isochronal annealing experiments for TiN/HfSiON/Si, it was found that positively charged defects (such as V_o) were introduced into HfSiON after annealing at 700-900°C. These defects were introduced by the interaction between TiN and HfSiON, resulting in the formation of polycrystalline TiO₂ at the interface. The positively charged defects were annealed out at 1100°C, but the dielectric properties of HfSiON degraded.