Multi-step ion beam etching of sub-30 nm magnetic tunnel junctions for reducing leakage and MgO barrier damage

Abstract

We have demonstrated the fabrication of sub 30 nm magnetic tunnel junctions (MTJs) with perpendicular magnetic anisotropy. The multi-step ion beam etching (IBE) process performed for 18 min between 45 degrees and 30 degrees, at 500 V combined ion supply voltage, resulted in a 55 nm tall MTJ with 28 nm diameter. We used a negative tone electron beam resist as the hard mask, which maintained its lateral dimension during the IBE, allowing almost vertical pillar side profiles. The measurement results showed a tunnel magneto-resistance ratio of 13% at 1 k Omega junction resistance. With further optimization in IBE energy and multi-step etching process, it will be possible to fabricate perpendicularly oriented MTJs for future sub 30 nm non-volatile magnetic memory applications.