The thermal stability and electrical properties of W2N/Ta 2O5/Si metal oxide semiconductor (MOS) capacitors upon post-metal annealing in H2 or N2 + H2 ambient at 400-600°C for 30 min are investigated. After annealing at 400-500°C, the W2N gate remains intact but, due to loss of nitrogen, partly transforms to WO3 after annealing at 600°C. The partial oxidation of W2N is more noticeable when annealing in H2 ambient than in N2 + H2, and also induces greatly increased resistivity. However, the capacitance-voltage (C-V) curves of the W 2N/Ta2O5/Si MOS capacitors are similar before and after post-metal annealing. C-V hysteresis measurements showed that charges within the Ta2O5 layer of the as-fabricated MOS structure are positive, and the density is 4.94 × 1012 cm-2. After annealing in H2, the charge density decreased with increasing annealing temperature, and the charge polarity became negative after annealing at 600°C. In N2 + H2, the charge polarity became negative right after annealing at 400°C, and the density was below 10 12 cm-2. For the I-V curves, the leakage current decreases with increasing annealing temperature at positive bias, and H2 annealing results in lower leakage currents than N2 + H2 annealing. In contrast, the leakage currents are all similar when the samples are stressed at negative bias, regardless of the annealing temperature and ambient.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry