Stabilization of\nTetragonal Phase in Hafnium Zirconium\nOxide by Cation Doping for High‑K Dielectric Insulators

As electronic circuit integration intensifies, there\nis a rising\ndemand for dielectric insulators that provide both superior insulation\nand high dielectric constants. This study focuses on developing high-k\ndielectric insulators by controlling the phase of the Hf<sub>0.5</sub>Zr<sub>0.5</sub>O<sub>2</sub> (HZO) film with additional doping,\nutilizing yttrium (Y), tantalum (Ta), gallium (Ga), silicon (Si),\nand aluminum (Al) as dopants. Doping changes the ratio of tetragonal\nto monoclinic phases in doped HZO films, and Y-doped HZO (Y:HZO) films\nspecifically exhibit a high tetragonal phase ratio and a dielectric\nconstant of 40.9, indicating superior insulating properties compared\nto undoped HZO films. To clarify the fundamental mechanism driving\nthe enhancement in dielectric properties, we have carried out various\nanalyses combined with density functional theory (DFT) calculations.\nThrough the optimization of the post-deposition annealing (PDA) process\nand the heterojunction structure with Al<sub>2</sub>O<sub>3</sub>,\nan Al<sub>2</sub>O<sub>3</sub>/Y:HZO heterojunction with a high dielectric\nconstant and even lower leakage current compared to a single layer\nwas developed. The thin-film transistor (TFT) with the Au/Ti/amorphous\nInGaZnO<sub>4</sub> (a-IGZO)/Al<sub>2</sub>O<sub>3</sub>/YHZO/TiN\nheterojunction structure exhibits low subthreshold swing (SS) values\nwithin a narrow gate-source voltage (<i>V</i><sub>sg</sub>) range. This study advances knowledge on how the controlled-phase\ndoped HZO films affect the dielectric constant and leakage current\nand will contribute to semiconductor technology advancements by overcoming\nthe limitations of conventional high-k dielectric insulators.