Rational design of selective thermal atomic layer etching processes through computational chemistry

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Thermal atomic layer etching (ALE) is a new path for isotropic etching of materials with atomic-scale precision. By proper selecting the etchants and tuning the processing parameters, thermal ALE can be applied for selective patterning of nanostructures. This technology is very promising for the fabrication of advanced semiconductor devices, such as gate-all-around transistors and 3D NAND flash memories. A major obstacle to establish new ALE processes by experimental trials is the limited predictive ability. In SELETCH, we propose to use rational design to accelerate the development of thermal ALE processes. To achieve this, theoretical calculations based on computational chemistry will be performed to investigate well-established ALE processes (e.g. ALE of Al2O3). Based on in-depth knowledge of the reaction mechanisms, we aim to establish reliable and simple descriptors to predict the reactivity of etchants towards different materials. Next, large-scale virtual screening is carried out to identify candidate etchants with desired reactivity and selectivity. The performance of those initial candidates is further evaluated through detailed theoretical calculations, including frequency calculation, COSMO-RS (conductor-like screening model for real solvents) modeling, ab initio thermodynamic calculation, and kinetic analysis. Finally, we expect to discover promising new etchants and suggest them for experimental verification. The SELETCH project will improve our fundamental understanding of the selectivity in thermal ALE. The proposed rational design approach is also potentially applicable to other chemical vapor processes, such as chemical vapor deposition and atomic layer deposition. More broadly, this project will promote the role of computational chemistry in industrial process development and thus facilitate the introduction of new materials-enabled products in semiconductor manufacturing.