GG-01: Study of Grain-Patterned Highly Ordered L10-FePt HAMR Media Using Reactive Molecular Dynamics Method

Embedded Hard-mask Patterning (EMP) has been proposed as a cost-effective fabrication method to be capable of patterning sub 5-nm grain sizes on highly-ordered L10-FePt media for Heat-Assisted Magnetic Recording (HAMR) [1]. Understanding the etching patterning mechanism of FePt is critical to maintain the highly-ordered L10 structure and low damage to the magnetic grains. In this research, Reactive Molecular Dynamics (MD) modeling is developed to study methanol (MeOH) plasma etch on highly-ordered continuous L10-FePt media film. Reactive interactions between the main plasma product etchant CO/H2 molecules and Fe/Pt atoms are studied using a modified embedded atom method (MEAM) interatomic potential and a bond-order based ReaxFF force field with atomic charge equilibration. As in L10-FePt thin film, Fe and Pt atoms are sitting in alternating layers in <001> directions, these interaction mechanisms are studied on Fe and Pt terminated surface respectively. It shows upon the dissociation of the CO ligand deposited at low energy (<10 eV) strong Fe-C interactions lead to Fen-C cluster formation as volatile product on the Fe-terminated surface. On the Pt-terminated surface, however, C-Pt interaction does not form any form of cluster volatile product. Dissociated C atoms also interact with Fe atoms under the Pt-layer and therefore can create crystal structure defects. The chemical yield without any physical ion sputtering is 4-5X higher on the Fe-terminated surface than on the Pt-terminated surface. The before and after etched media film is also analyzed with virtual XRD method to show the chemical ordering change from the plasma treatment. This study uncovered not only the etching mechanism of high methanol etch rate on Fe-based magnetic materials but also the magnetic material damage mechanism.References: [1] H. Wang et al., Appl. Phys. Lett. 102, 052406 (2013). [2] J. Zhu et al., IEEE Trans. Magn. Vol 52, No.7 (2016).