Thermal Atomic Layer Etching of Amorphous and Crystalline Hafnium Oxide, Zirconium Oxide, and Hafnium Zirconium Oxide

Thermal atomic layer etching (ALE) using the fluorination and ligand-exchange mechanism was employed to etch amorphous and crystalline films of hafnium oxide, zirconium oxide, and hafnium zirconium oxide. HF was the fluorination reactant and dimethylaluminum chloride (DMAC) or titanium tetrachloride was the metal precursor for ligand-exchange. The amorphous films etched faster than the crystalline films. The differences were most pronounced for hafnium oxide. At 250°C, the etch rate was 0.03-0.08 Å/cycle for crystalline HfO
₂
and 0.68 Å/cycle for amorphous HfO
₂
.