Effects of atomic layer etching on magnetic properties of CoFeB films: Reduction of Gilbert damping

Atomic layer etching (ALE) is an emerging technology to etch thin films with atomic level precision for microelectronics industry applications. This approach has been previously demonstrated to work on a number of materials; however, in most cases, only electronic properties of these materials following ALE are investigated. Since ALE of complex magnetic materials is extremely important for use in magnetic tunnel junctins (MTJs), it is imperative to understand how this etching approach affects the magnetic properties of the corresponding films. In this work, we studied the surface morphology, elemental composition, and most importantly, the magnetic properties of the technologically relevant magnetic alloy CoFeB before and after ALE treatment, and compared with the traditional ion milling etching technique. Through ferromagnetic resonance measurements, we find while the change in the saturation magnetization from ALE is small, the Gilbert damping of CoFeB is reduced by 11–35%, possibly due to the suppressed two-magnon scattering processes on the sample surface. Our results show that ALE can be used to etch CoFeB nondestructively and may even improve its magnetization dynamics properties.