Electrical characterization and process control of cost-effective high-k aluminum oxide gate dielectrics prepared by anodization followed by furnace annealing

A cost-effective technique was introduced to prepare ultrathin aluminum oxide (Al₂O₃) gate dielectrics with equivalent oxide thickness (EOT) down to 14 Å. Al₂O₃ was fabricated by anodic oxidation (anodization) of ultrathin Al films at room temperature in deionized water and then furnace annealed at 650°C in N₂ ambient. Both dc and dac (dc superimposed with ac) anodization techniques were investigated. Effective dielectric constant of k∼7.5 and leakage current of 2-3 orders of magnitude lower than SiO₂ are observed. The conduction mechanism in Al₂O₃ gate stack is shown to be Fowler-Nordheim (F-N) tunneling. Saturated current behavior in the inversion region of MOS capacitor is observed. It is found that the saturation current is sensitive to interface state capacitance and can be used as an efficient way to evaluate the Al₂O₃ gate stack/Si-substrate interfacial property. An optimal process control for preparing Al₂O₃ gate dielectrics with minimized interface state capacitance via monitoring the inversion saturation current is demonstrated.