Probing magnetic properties of STT-MRAM devices down to sub-20 nm using spin-torque FMR

Abstract

Scaling STT-MRAM cells beyond 1X technology nodes will require MTJ devices smaller than 30 nm. For such small sizes, process-induced damage becomes a primary factor of device performance. A robust method of assessing magnetic properties of sub-30 nm devices is thus needed. Here we report measurements of the anisotropy field H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</sub> down to 20 nm devices using ST-FMR. We show that H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</sub> increases for decreasing sizes. The interfacial anisotropy field exceeds 23 kOe, leading to Hk larger than 13 kOe for 20 nm devices under optimal process conditions. Using insight from micromagnetic simulations, we develop a simple model to fit Hk size dependence, allowing us to quantify magnetic edge damage for various process conditions.