In situ XPS study on atomic layer etching of Fe thin film using Cl2 and acetylacetone

Abstract

Etching of transition metals is one of the major challenges in magnetic random-access memory fabrication. In this work, atomic layer etching of iron surfaces with halogen and an organic molecule was studied. The authors successfully etched Fe thin films by forming volatile metal complexes at low temperature with cyclic reactions of Cl2 and acetylacetone (acac). The mechanism of acac reacting on Cl-modified Fe surface was investigated: the surface was first activated with Cl2 gas, and then the top layer of metal was removed by acac reaction. The extent of Cl2 reaction determined the etching rate. At substrate temperatures lower than 135 °C, acac could not remove chlorine. In situ x-ray photoelectron spectroscopy and density functional theory simulation show that the reaction of acac on Cl-dosed Fe surface is likely following a complex pathway instead of simple acac substitution for Cl2. Acac decomposition may play an important role in the process.