Preparation by pulsed laser deposition and characterization of ZrO2, HfO2 and PrOx thin films for high-k gate insulator

High-k thin films of ZrO₂, HfO₂ PrO_x of ∼10 nm thickness have been prepared by pulsed laser deposition (PLD), and characterized in microscopic structure and electrical properties. Crystallization is promoted in ZrO₂ films deposited above 400°C, but a significant XRD peak was not observed in the ZrO₂ film grown below 400°C. Moreover, density of the film is confirmed to saturate above 400°C by grazing incident angle X-ray reflectance. The leakage current is decreased by increasing growth temperature, but an equivalent-oxide thickness (EOT) obtained from accumulation capacitance of C - V characteristics becomes large. HfO₂ films show the similar behaviors to ZrO₂ films. The films deposited at 400°C were annealed at 400°C in O₂ gas to reduce the leakage, but the EOTs become large. So, these films were irradiated with oxygen radical at the pressure of 10^-3 Pa both to prevent the growth of interfacial layer and to enhance the oxidation of only the films. Although the leakage of ZrO₂ films can be reduced by oxygen radical irradiation, only small improvement is observed in the PrO_x films.