Ion-Assisted Plasma Etch Modeling of L1₀ Phase FePt Magnetic Media Fabrication with Embedded Mask Patterning Method

The embedded mask patterning (EMP) method uses a plasma etching process to form an ultrasmall grain size (∼ 4nm), but thermally stable isolated L1₀-FePt magnetic grains with an embedded Ru hard mask. EMP demonstrated as a promising and potentially cost-effective solution to fabricate ultrahigh density magnetic media for heat-assisted magnetic recording. In this simulation study, we investigated the manufacturability of formation of these high aspect ratio (AR), nanometer-sized spaced grains in a methanol (MeOH)/Ar plasma etch process used to etch FePt layer through Ru mask opening and to form a volatile Fe-carbonyl product. We developed a model based on the ion-neutral synergy model, and included the effect of potentially redeposited etch product inside the high AR narrow grain spacing by calculating the redeposition flux distribution in addition to neutral and ion flux coverage over the etch surface. Our simulation shows that the redeposition rate increases as etching progresses deeper into the substrate, which significantly reduces the etch rate inside the high AR features and produces nonuniform etched depth across the grain boundary distribution, which may lead to under-etched grain spacing and degrade media magnetic properties. The etch rate model is combined with a developed 2-D level set computational program to study the redeposition-induced defects pattern defects. Micromagnetic simulation also shows these defects can be responsible for the experimental observed media magnetic properties change.