Preparation and properties of Ta2O5 film capacitors using TiSi2 bottom electrode

Thin Ta2O5 films were grown in a low pressure chemical vapor deposition(LPCVD) reactor. The Al/Ta2O5/p-Si and Al/Ta2O5/TiSi2/p-Si capacitors were fabricated and their capacitor characteristics were investigated. During a dry O2 annealing process of the Ta2O5, the oxidation of Si substrate and TiSi2 layer underneath the Ta2O5 layer was observed resulting in formation of SiO2 and TiO2 on their surfaces, respectively, due to the oxygen diffusion through the Ta2O5 layer. As-deposited 100 nm thick Ta2O5 film was found to be crystallized to δ-Ta2O5 at a temperature of about 700°C. The crystallized Ta2O5 film showed a higher leakage current density for the Al/Ta2O5/p-Si capacitor, compared to an amorphous Ta2O5 film. For the Al/Ta2O5/TiSi2/p-Si capacitor, on the other hand, the leakage current characteristic was improved as the annealing temperature increased. Capacitance of the capacitor was found to also increase as the annealing temperature increased. The Al/Ta2O5/TiSi2/p-Si capacitor, however, has failed to show the better capacitor characteristics over the conventional Al/Ta2O5/p-Si capacitor.