Characterization of Defect States Responsible for Leakage Current in Tantalum Pentoxide Films for Very-High-Density Dynamic Random Access Memory (DRAM) Applications

Defect states in tantalum pentoxide films grown by low-pressure metal-organic chemical vapor deposition on silicon wafers have been studied with Al/Ta2O5/p+-Si and Al/Ta2O5/n+-Si capacitor structures by the zero-bias thermally stimulated current technique. It was demonstrated that a shallow band of defect states is responsible for leakage current. The shallow band of defect states can be suppressed by low-temperature post metallization annealing, resulting in a reduction of leakage current for both positive gate bias and negative gate bias. However, the reduction in leakage current for positive gate bias is much stronger than that for negative gate bias.