Electrical characterization of metal–oxide–semiconductor capacitors with anodic and plasma-nitrided oxides

Abstract

We have studied two novel techniques that should inherently be more uniform than current mainstream processes used to produce silicon dioxide or nitrided-oxide gate insulators. Anodic films were fabricated by anodizing Si wafers in HCl solutions, and thermal oxide films were nitrided in N2O plasmas produced with an electron-cyclotron resonance source. Using typical polysilicon-gate test structures, the electrical characteristics are obtained and compared to thermal oxides. Both techniques can produce thin films (<15 nm thick) with interface state densities and leakage currents initially comparable to their thermal oxide counterparts, if the films are subjected to rapid thermal annealing at temperatures of 950 °C. The annealed films are subjected to high-field (⩾8 MV/cm) Fowler–Nordheim stress and the buildup of trapped charge is monitored as a function of time. Anodic films are found to have moderately higher bulk and interface trap generation rates than the thermal control. Thinner anodic oxides, which were grown at slower rates, had better properties than thicker anodic oxides, suggesting that even slower growth rates could yield anodic oxides with improved electrical properties.