Isotropic atomic layer etchings of various materials by using dry chemical removal

Abstract

Abstract Isotropic atomic layer etching (ALE) has become an essential technology for the fabrication of logic transistors beyond 2 nm generation and NAND memory with more than 100 layers of stacking. There are promising etching technologies for isotropic ALE, such as reaction-limiting, modification-limiting and ligand exchange processes. In this work, isotropic ALEs undertaken using dry chemical removal (DCR) tools are discussed. In DCR, radicals from plasma are delivered to enhance the surface modification. In addition, the wafer temperature quickly changed due to infrared light and electric static chuck for adsorption and desorption accelerations. Silicon ALE can be realized by the combination of surface oxidation and removal by HF vapor. SiO2 can be etched by the alternate flows of HF and NH3 followed by wafer heating. SiN, TiN and W can be etched at nanometer precision by using fluorination with hydrofluorocarbon radicals and heating. Co and LaO can be etched with diketone exposure and heating.