In-situ low temperature N2O plasma annealing for high-dielectric Ta2O5 thin films

PECVD Ta2O5 him was deposited by using in-situ low temperature N2O plasma annealing during the film deposition. N2O plasma annealing led to excellent leakage current characteristics and good C-V characteristics of Ta2O5 films, especially, multi-step annealing was more effective in reducing the leakage current than single-step annealing. The low field leakage current of multi-step annealed films was significantly reduced to 10(-8) A/cm(2), for a negative bias of 1 MV/cm, whereas that of single-step annealed films was 10(-4) A/cm(2). The stable dielectric constants, ranging from 23 similar to 25, were obtained. Improvement of electrical properties was attributed to the filling of oxygen vacancy and the reduction of impurities, such as, carbon and hydrogen, included in the as-deposited films by N2O plasma annealing. Especially, multi-step annealed films showed lower level of impurities than those of single-step annealed films. As a result, in-situ multi-step N2O plasma annealing is promising to ensure an excellent quality of Ta2O5 films at low temperature.