Rational design of selective thermal atomic layer etching processes through computational chemistry
Final Report Abstract
Theoretical calculations were performed to understand reaction mechanisms of thermal atomic layer etching (ALE) processes, aiming to guide the development of new processes. In the first case study, the thermal ALE of Al2O3 using HF and AlMe3 (Me = CH3) was examined. Thermodynamic modeling and density functional theory (DFT) calculations revealed a two-step mechanism for AlF3 etching by AlMe3, where an AlF3-xMex layer first formed on the surface and was then removed by forming volatile dimers with AlMe3. This reaction mechanism was applied to discover potential new etchants for thermal Al2O3 ALE. Subsequently, theoretical calculations were performed to study the thermal ALE of metallic Cu, a crucial material in the back-end-of-line metallization. While Cl2 was considered as a potential co-reactant for Cu ALE, it required a higher reaction temperature than O2 or O3. DFT calculations using surface models indicated that the desorption of etch products from the surface is the rate-limiting step. To discover new etchants for Cu ALE, a "reverse engineering" approach was proposed, which involves starting with the desired etch products and working backwards to determine the required etchants. This approach not only ensures that the etch product meets the required stability and volatility, but also simplifies the search for a suitable etchant.
Publications
-
Ab initio study on the surface reactions of thermal atomic layer etching of Al2O3. The AVS 20th International Conference on Atomic Layer Deposition. 2020, Belgium.
Xiao Hu, Jörg Schuster & Stefan Schulz
-
Ab initio calculations on the thermal atomic layer etching of copper. The AVS 22th International Conference on Atomic Layer Deposition. 2022, Belgium.
Xiao Hu & Jörg Schuster
-
Chemical Mechanism of AlF3 Etching during AlMe3 Exposure: A Thermodynamic and DFT Study. The Journal of Physical Chemistry C, 126(17), 7410-7420.
Hu, Xiao & Schuster, Jörg
