High-k Al2O3 gate dielectrics prepared by oxidation of aluminum film in nitric acid followed by high-temperature annealing

A simple, cost-effective, and room temperature process was proposed to prepare high-k gate dielectrics. An aluminum oxide (Al₂O₃) gate dielectric was prepared by oxidation of ultrathin Al film in nitric acid (HNO₃) at room temperature then followed by high-temperature annealing in O₂ or N₂. The substrate injection current behavior and interface trap-induced capacitance were introduced to investigate the interfacial property between the gate dielectric and Si substrate. Al₂O₃ gate dielectric MOS capacitors with and without initial SiO₂ layers were characterized. It was shown that the Al₂O₃ gate dielectrics with initial oxide exhibit better electrical properties than those without. The 650°C N₂-POA Al₂O₃-SiO₂ sample with an equivalent oxide thickness of 18 Å exhibits three orders of magnitude reduction in gate leakage current in comparison with the conventional thermal SiO₂ sample.