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，位于博尔德的科罗拉多大学的Steven乔治教授研究了热原子层蚀刻（ALE）中涉及的基本化学问题。 过去50年来最伟大的成就之一是半导体器件的逐步小型化。这种进展由“摩尔定律”描述，该定律指出晶体管的尺寸大约每两年减小一半。 随着小型化的继续，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的特征尺寸。原子层蚀刻（ALE）技术最近已经出现，以提供对蚀刻工艺的控制，使得可以在单个步骤中去除单个原子层。 乔治教授采用了许多技术来确定原子层灵敏度的沉积或去除的材料量。这些实验也能够测量材料去除，并确定在蚀刻过程中存在的表面物种。这项研究对于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。该研究是跨学科的，涉及从基础科学到工程应用的学生。乔治博士和他的小组成员还积极地通过出版物和在科学会议上的许多演讲来提供他们的结果。在这个项目中，乔治博士探讨了热ALE过程，导致原子层控制蚀刻。热ALE过程是基于顺序和自限制的表面吸附和配体交换反应。表面氟化反应是热化学有利的，并产生具有单层量级表面覆盖的金属氟化物。配体交换反应类似于有机金属化学中众所周知的金属转移反应。本研究调查了各种前体和反应产物的反应和配体交换反应，并检查这些反应对温度和其他反应条件的依赖性。本研究亦探讨了蚀刻制程的保形性，并探讨了薄膜结构对蚀刻的影响。对这些反应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，这些反应对先进的半导体制造非常重要，并对该领域产生了更广泛的影响。乔治博士让本科生和研究生参与他的研究，并积极参与科学推广。他的研究成果在各种科学会议上广泛发表，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.