Low damage smoothing of magnetic material films using a gas cluster ion beam

This paper proposes a low damage smoothing process for magnetic materials using a gas cluster ion beam (GCIB). In order to achieve low damage processing, the effect of incident angle was investigated. Depth profiles of major elements constituting the films were measured by secondary ion mass spectroscopy (SIMS). The film structure and the lattice spacing were obtained by X-ray reflectivity (XRR) and grazing incident X-ray diffraction (XRD), respectively. After the GCIB irradiation at an acceleration voltage of 20 kV and incident angle of 80° with simultaneous rotation, a smooth surface of a PtMn film was obtained, with an average roughness of 1.2 nm. A damaged layer thickness of less than 1.5 nm was achieved under these conditions. Using the oblique GCIB irradiation, the PtMn film was etched without any change in the strain profile. Thus, the GCIB could be utilized to obtain surfaces of magnetic devices with extremely shallow damage.