Fabrication and Metrology of Novel Magnetic Tunnel Junctions in the Ultra-thin Barrier Limit

Magnetic tunnel junctions, nanostructured by highly charged ions, are being probed and characterized to establish the foundation for novel magnetic random access memory architectures expected to replace hard drives and already components in current technologies.

Within a broader program of exploring methods to fabricate structures with novel electronic properties at the nanometer scale, we are using highly charged ions (HCIs) to produce ensembles of nano-features within magnetic tunnel junctions (MTJs). Technologically, MTJs are a major component of magnetic random access memory (MRAM) architectures which are expected to eventually replace hard drives and are already standard components in automotive and aviation applications. A leading technical challenge is producing MTJs whose resistance-area (RA) product (two dimensional resistivity) fall in a range that allows for both high signal-to-noise, fast write times, and long lifetimes. Our approach is to produce a layer structure that is a superposition of high and low RA product regions, whose average RA product is determined by the relative density of each. Our strategy is to irradiate highly quality oxides with very dilute doses of highly charged ions (HCIs) that introduce local regions of thinned oxide at each individual ion’s impact site, as shown in the adjacent figures. The HCI impact sites result in ultra-thin (< 1 nm) regions of the tunnel barrier. The unique properties of these unusual MTJs have precipitated the development of new device modeling and measurement techniques.