Surface Reaction Mechanisms of Atomic Layer Etching and High-Aspect-Ratio Reactive Ion Etching
While the miniaturization of semiconductor devices is now approaching the atomic-scale limit, the demand for higher performance of computer chips is ever growing. This trend has driven new device technologies such as three dimensional structures and new materials, which also demands further innovation in process technologies. As the device sizes are now close to the atomic scale, the required accuracy of processing is also at the atomic scale with little or no damage to the surface critical for device performance. In this sense, ion bombardment energy of typical plasma processes needs to be lowered as much as possible in general (except for some specific applications), which makes surface chemical reactions play more important roles. When new materials are used, new surface chemical reactions must be explored to achieve what is needed in the process. The author and his research group members have analyzed surface chemistries of various materials such as Si based materials, metal, and metal oxides, mostly for the purpose of reactive ion etching (RIE) and atomic layer etching (ALE), using beam experiments and molecular dynamics (MD)/first-principle quantum mechanical (QM) simulations. In this presentations, some of our latest results on etching mechanism analyses for RIE of SiN, ALE of SiO2, and thermal ALE of metal with hexafluoroacetylacetone (hfacH) will be presented.