Annealing temperature-dependent microstructure and optical and electrical properties of solution-derived Gd-doped ZrO₂ high-k gate dielectrics

In current work, the microstructure and optical and electrical properties of sol–gel-derived Gd-doped ZrO₂ gate dielectric thin films as functions of annealing temperatures were systemically investigated. Analyzes by x-ray diffraction have indicated that the 240 °C-baked sample as well as those samples annealed at lower temperatures keep amorphous state. In the sample annealed at 500 °C, however, the amorphous phase disappears and tetragonal ZrO₂ is formed. Measurements from ultraviolet-visible spectroscopy (UV/Vis) have demonstrated that transmittance of all samples in the visible region is approximately 80% and the increase in band gap energy has been found with increasing the annealing temperature. Electrical properties of all samples based on Al/Si/ZrGdO_x/Al MOS capacitor have been investigated by using semiconductor device analyzer. Through the analysis and calculation of the electrical characteristic curves, solution-processed Al/ZrGdO_x/Si/Al capacitor shows improved performances at a annealing temperature of 400 °C, such as high dielectric constant (k) of 16.56, lowest oxidation charge density (Q _ox) of −0.74 × 10¹² cm⁻², and boundary trap oxidation charge density (N _bt) of 3.17 × 10¹² cm⁻². In addition, the leakage current mechanism for 400 °C-annealed sample has been discussed in detail.

solution-processed Gd-doped ZrO₂ gate dielectric films were realized. Al/ZrGdO_x/Si/Al capacitor shows optimized and improved performances at a annealing temperature of 400 °C.