Effect of Annealing Temperature on the Structural, Optical, and Electrical Properties of Al-Doped ZrO2 Gate Dielectric Films Treated by the Sol–Gel Method

Abstract

In this article, we report the preparation of Al-doped ZrO2 (AZO) thin films by the sol–gel method. The electrical properties, microstructure, and optical properties of AZO high-k gate dielectric films at different annealing temperatures were systematically investigated. XRD results confirm that the AZO film was amorphous at a temperature of 600 °C, and Al doping raises the crystallization temperature of ZrO2. AFM and FESEM show a smooth surface of AZO film without cracks. As the annealing temperature increased from 600 to 900 °C, all of the films had similar RMS roughness under 1 nm, the film thickness decreased accordingly, the bandgap value increased from 5.77 to 5.82 eV, the valence band shift (ΔEv) increased, and the conduction band shift (ΔEc) decreased. XPS analysis showed that silicates were formed at the AZO/Si interfacial layer. Electrical performance tests showed that high-temperature annealing can effectively improve the electrical properties, as shown by the increase in dielectric constant (k) and the decrease in flat-band voltage (ΔVfb). However, an increase in leakage current density with increasing annealing temperature was observed due to the decrease in ΔEc and the appearance of crystallization caused by the increase in annealing temperature.

Electronic properties of ZrO2 films fabricated via atomic layer deposition on 4H-SiC and Si substrates

“…In accordance with the experimental results in figure 5, the sample with a high-k insulating layer, i.e., the Al/ZrO 2 /Si/Al (SiC MOS) structure, had the larger breakdown voltage of 25.9V relative to that of the Al/ZrO 2 /SiC/Al (Si MOS) structure, with a leakage current of 1 × 10 −8 A/cm under a zero gate voltage. Although the ZrO 2 /SiC MOS structure achieves relatively high breakdown voltages (V B = 23V) [26][27][28], the application of ZrO 2 as a High-k material on its own as a gate oxygen layer is somewhat unsatisfactory when compared to the performance of conventional SiO 2 applications on Si as well as SiC substrates [29]. This may be due to the low valence band offset of ZrO 2 (ΔE V = 0.52 eV) [8,30].…”