Preparation and properties of Ta₂O₅ film capacitors using TiSi₂ bottom electrode

Abstract

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.