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[摘要]：HfO2/TiO2 bilayered thin films were grown on Ru and TiN electrodes at 250 degrees C by atomic layer deposition. The crystalline structure of the HfO2 layer was affected by the crystalline structure of the TiO2 under-layer. The HfO2 layer grown on an anatase-structured TiO2 layer crystallized into a monoclinic structure with a dielectric constant of similar to 16, whereas the HfO2 layer grown on rutile-structured TiO2 contained a mixture of tetragonal (or cubic) and amorphous phases. This mixed structured-HfO2 film had a higher dielectric constant of similar to 29. The formation of tetragonal HfO2 on the rutile structured TiO2 resulted from the structural compatibility of the specific planes of the tetragonal HfO2 and rutile structured TiO2. The thin HfO2 layer with the higher dielectric constant deposited on rutile TiO2 suppressed the leakage current effectively. Consequently, an equivalent oxide thickness of 0.41 nm from the HfO2/TiO2 bilayer (thickness of HfO2 and TiO2 was 0.5 and 6 nm, respectively) was achieved with a leakage current of similar to 2 x 10(-7) A/cm(2) at an applied voltage of 0.8 V. |
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