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

热原子层刻蚀（ALE）是一种具有原子尺度精度的材料各向同性刻蚀新途径。通过选择合适的蚀刻剂和调整工艺参数，热ALE可以用于纳米结构的选择性图像化。这项技术在制造先进的半导体器件，如栅极全能晶体管和3D NAND闪存方面非常有前途。通过实验试验建立新的ALE过程的一个主要障碍是有限的预测能力。在SELETCH中，我们建议使用合理的设计来加速热ALE工艺的发展。为了实现这一目标，将进行基于计算化学的理论计算，以研究已建立的ALE过程（例如Al2O3的ALE）。基于对反应机理的深入了解，我们的目标是建立可靠和简单的描述符来预测蚀刻剂对不同材料的反应性。接下来，进行大规模的虚拟筛选，以确定候选蚀刻剂所需的反应性和选择性。通过详细的理论计算，包括频率计算、cosmos - rs（真实溶剂类导体筛选模型）建模、从头计算热力学计算和动力学分析，进一步评估这些初始候选材料的性能。最后，我们期望发现有前途的新蚀刻剂，并建议它们进行实验验证。SELETCH项目将提高我们对热ALE选择性的基本理解。提出的合理设计方法也可能适用于其他化学气相沉积工艺，如化学气相沉积和原子层沉积。更广泛地说，该项目将促进计算化学在工业过程开发中的作用，从而促进半导体制造中新材料产品的引入。

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.