Abstract
Plasma etching process of single-crystal L10-FePt media [H. Wang et al., Appl. Phys. Lett. 102(5) (2013)] is studied using molecular dynamic simulation. Embedded-Atom Method [M. S. Daw and M. I. Baskes, Phy. Rev. B 29, 6443 (1984); X. W. Zhou, R. A. Johnson and H. N. G. Wadley, Phy. Rev. B 69, 144113 (2004)] is used to calculate the interatomic potential within atoms in FePt alloy, and ZBL potential [J.F. Ziegler, J. P. Biersack and U. Littmark, “The Stopping and Range of Ions in Matter,” Volume 1, Pergamon,1985] in comparison with conventional Lennard-Jones “12-6” potential is applied to interactions between etching gas ions and metal atoms. It is shown the post-etch structure defects can include amorphized surface layer and lattice interstitial point defects that caused by etchant ions passed through the surface layer. We show that the amorphized or damaged FePt lattice surface layer (or “magnetic dead-layer”) thickness after etching increases with ion energy for Ar ion impacts, but significantly small for He ions at up to 250eV ion energy. However, we showed that He sputtering creates more interstitial defects at lower energy levels and defects are deeper below the surface compared to Ar sputtering. We also calculate the interstitial defect level and depth as dependence on ion energy for both Ar and He ions. Media magnetic property loss due to these defects is also discussed.
Highlights
EMP process is proposed to enable ultra-small HAMR media grains by defining isolated L10FePt grains through a granular hard-mask layer using ion-assisted methanol plasma etch process.[1]
The amorphous layer thickness reaches from 4 mono-layers at 50eV to 14 mono-layer under Ar ion energy at 250eV
ZBL potential of Fe or Pt for He is almost one order of magnitude lower than that for Ar, giving the result of higher depth of embedded He ions inside FePt lattice.Fig. 11 shows the number of embedded particles after 500 ion impacts
Summary
EMP process is proposed to enable ultra-small HAMR media grains by defining isolated L10FePt grains through a granular hard-mask layer using ion-assisted methanol plasma etch process.[1] In our previous modeling of EMP process, we applied a levelset analytic model with Langmuir surface kinetics to study ion and neutral effect in patterning Ru hard-mask and FePt media grains.[2,3] We found that it is critical to minimize the hard-mask erosion by reduce the ion sputtering yield on the hard-mask and to maximize the chemical etch selectivity between hard-mask and FePt media, in order to successfully define the nano-meter scaled FePt grains. Classical Molecular Dynamics (MD) simulation has been used to understand the ion sputtering and surface reaction kinetics during etching process.[9,12,13,14] In MD model of etch process, substrate atoms, etchant particles (ions) and neutrals (molecules) are constructed in one ensemble with defined interatomic potentials. Barone et al performed MD study of Si etch of F+ as well as Cl+ ions[14] and characterized both physical sputtering and chemical sputtering process
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
