The magneto-optical Kerr effect for efficient characterization of thermal stability in dense arrays of p-MTJs

Abstract

Magnetic Random Access Memory (MRAM) targeting cache memory replacement consists of high density arrays of perpendicular Magnetic Tunnel Junctions (p-MTJs). One of the key advantages to MRAM is its non-volatility, where the measurement of retention is critical. However, evaluating the thermal stability of high density arrays is both time consuming and requires electric read out of many functional devices. It is shown that by using the Magneto-Optical Kerr Effect (MOKE) to measure the magnetic after-effect at fixed fields, efficient and in-line characterization of both the magnetic properties and data retention is possible. This is qualified through cross measurement of multiple dies using both MOKE and electrical readout of a Mbit array. Data from both techniques is then fitted using a macrospin model where the values of both Δ and Hk are shown to come within 10% of each other.