Engineering the nm-thick interface layer formed between a high-k film and silicon
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The interface layer between thin sputter-deposited tantalum oxide (TaO x) high-k film and silicon substrate was engineered with the Hf doping method and the insertion of a thin 5 TaN x interface. The following results have been obtained: 1) the Hf dopant in the TaO x film was involved in the interface formation process, e.g., forming a new, thinner high-k HfSi xO y interface layer rather than the SiO x layer, 2) when the TaN x interface was inserted, the interface layer composition was even more complicated, e.g., including TaO xN y and HfSi xO y structures. No hafnium nitride or oxynitride was detected, 3) the interface layer structure was changed, e.g., from single-zone to multi-zone with different compositions, 4) when a low concentration of Hf existed in the TaO x film, the high-k dielectric properties, such as the k value, fixed charge density, dielectric strength, were improved, and 5) when the thin TaN x interface layer was inserted, the above electric properties were further improved. However, the fixed charge density and interface states were increased due to the insertion of the TaN x interface layer. These results were contributed by factors such as the charge-trapping characteristics in the interface layer and the some damage repairing mechanisms. In summary, this research proved that the high-k film's interface layer and bulk properties could be were improved with the doping process as well as the insertion of an ultra-thin TaN x interface film.
