Fundamental Issues for Thermal Atomic Layer Etching

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

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.