Thermal effect of annealing-temperature on solution-processed high-k ZrO₂ dielectrics

In this paper, a solution-processed zirconium oxide (ZrO₂) dielectric was deposited by spin coating with varying pre-annealing temperatures and post-annealing temperatures. The thermal effect of the pre-annealing and post-annealing process on the structural and electrical properties of ZrO₂ films was investigated. The result shows that the pre-annealing process had a significant impact on the relative porosity and internal stress of ZrO₂ film. A pre-annealing process with a low temperature could not effectively remove the residual solvent, while a high pre-annealing temperature would lead to large internal stress. As for post-annealing temperature, it was found that the post-annealing process can not only reduce internal defects of the ZrO₂ dielectric, but also optimize the interface between the semiconductor and dielectric by lowering the surface defects of the ZrO₂ film. Finally, the TFT with a pre-annealing temperature of 200 °C and post-annealing temperature of 400 °C showed optimized performance, with a mobility of 16.34 cm² (V s)^-1, an I _on/I _off of 2.08 × 10⁶, and a subthreshold swing (SS) of 0.17 V dec^-1.