Fundamental Issues for Thermal Atomic Layer Etching

在这个由化学系大分子、超分子和纳米化学项目资助的项目中，科罗拉多大学博尔德分校的Steven George教授研究了涉及热原子层蚀刻（ALE）的基本化学问题。在过去的50年里，最伟大的成就之一就是半导体器件的逐步小型化。这一进展被“摩尔定律”所描述，摩尔定律指出晶体管的尺寸大约每两年减少一半。随着小型化的继续，人们对这些器件的制造方式提出了越来越高的要求，现在需要原子添加（沉积）和去除（蚀刻）方法来产生原子尺度上的特征尺寸。原子层蚀刻（ALE）技术最近出现，提供了对蚀刻过程的控制，从而可以在一个步骤中去除单层原子。乔治教授采用了许多技术，以原子层灵敏度来确定沉积或去除的材料数量。这些实验也能够测量材料的去除，并确定在蚀刻过程中存在的表面物种。这项研究对先进半导体器件的制造具有重要意义，并对电子和其他高科技产业产生直接影响。这项研究是跨学科的，涉及的学生的兴趣范围从基础科学到工程应用。乔治博士和他的小组成员也积极地通过出版物和在科学会议上的多次演讲来提供他们的研究结果。在这个项目中，George博士探索了导致原子层控制蚀刻的热ALE过程。热ALE过程是基于顺序和自限制的表面氟化和配体交换反应。表面氟化反应在热化学上是有利的，并产生表面覆盖单层数量级的金属氟化物。配体交换反应类似于有机金属化学中众所周知的金属转化反应。本研究考察了氟化反应和配体交换反应的各种前体和反应产物，并考察了这些反应对温度和其他反应条件的依赖性。本研究还探讨了蚀刻过程的一致性，并确定了薄膜结构对蚀刻的影响。对这些氟化和配体交换反应的理解定义了一个新的重要的表面反应家族，这对于先进的半导体制造很重要，并且在该领域具有更广泛的影响。乔治博士的研究涉及本科生和研究生，并积极参与科学推广。他的研究成果被广泛地发表在各种科学会议上，包括美国真空学会（AVS）和原子层沉积会议。

In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Steven George of the University of Colorado at Boulder studies the fundamental chemistry issues involved in thermal atomic layer etching (ALE). One of the greatest accomplishments in the last 50 years has been the progressive miniaturization of semiconductor devices. This progression is described by "Moore's Law" which states that transistors decrease in dimension by one-half approximately every two years. As miniaturization continues, increasing demands are placed on how these devices are made, and now it requires atom addition (deposition) and removal (etching) methods to produce feature sizes at the atomic scale. Atomic layer etching (ALE) techniques have recently emerged to provide control of the etching process so that a single layer of atoms can be removed in a single step. Professor George employs a number of techniques to determine the amount of material deposited or removed with atomic layer sensitivity. These experiments also are able to measure the material removal and to identify the surface species present during the etching process. This research is important for the fabrication of advanced semiconductor devices, and makes a direct impact on electronics and other high-technology industries. The research is interdisciplinary and involves students with interests ranging from basic science to engineering applications. Dr. George and his group members also actively make their results available through publications and numerous talks at scientific meetings. In this project, Dr. George explores the thermal ALE process that leads to atomic layer controlled etching. The thermal ALE process is based on sequential and self-limiting surface fluorination and ligand-exchange reactions. The surface fluorination reactions are thermochemically favorable and yield a metal fluoride with a surface coverage on the order of a monolayer. The ligand-exchange reactions are analogous to well-known transmetalation reactions in organometallic chemistry. This research investigates various precursors and reaction products for the fluorination and ligand-exchange reactions and examines the dependence of these reactions on temperature and other reaction conditions. This research also explores the conformality of the etching process and determines the effect of film structure on the etching. The understanding of these fluorination and ligand-exchange reactions defines a new important family of surface reactions that are important for advanced semiconductor fabrication and has broader impacts on the field. Dr. George involves undergraduate and graduate students in his research and is active in scientific outreach. The results of his research are widely presented at various scientific meetings including the American Vacuum Society (AVS) and Atomic Layer Deposition meetings.