Until now thermal atomic layer etching (ALE) have been established by fluorination and ligand-exchange reactions using HF as fluorination reactant and Sn(acac)2, Al(CH3)3, AlCl(CH3)2, and SiCl4. Here is a new study where TiCl4 is employed as a new metal chloride reactant for ligand-exchange.
In the study thermal HfO2 ALE using HF and TiCl4 as the reactants is investigated by in situ quartz crystal microbalance (QCM) measurements from 200 to 300 °C.
Further, an investigation into the selectivity of thermal ALE using HF and TiCl4 revealed that HfO2 and ZrO2 were etched by HF and TiCl4 but Al2O3, SiO2, Si3N4, and TiN were not etched. This is an important finding since all of those materials are typically used in Logic High-k Metal Gate stacks and various high-k capacitor applications.
Please find all the details in this Open Access publication by Younghee Lee and Steven M. George from the famous ALD/ALE lab at University of Colorado, in Boulder Colorado, USA.
Thermal atomic layer etching of HfO2 using HF for fluorination and TiCl4 for ligand-exchange
Younghee Lee and Steven M. George
Journal of Vacuum Science & Technology A 36, 061504 (2018); https://doi.org/10.1116/1.5045130