Tunneling magnetoresistance of perpendicular magnetic tunnel junction using L1₀ FePt electrodes on MgO/CrRu/TiN under-layers

A perpendicular magnetic tunnel junction (pMTJ) device was fabricated using L1₀ ordered FePt electrodes, which were deposited on MgO(8 nm)/CrRu(10 nm)/TiN(4 nm) under-layers. It was found that the MgO/CrRu/TiN under-layer helps lower the required FePt deposition temperature to below 400 °C, and provides a well-ordered bottom L1₀ FePt electrode with root-mean-square (RMS) surface roughness close to 0.4 nm. Magnetoresistance (MR) ratio and resistance-area (RA) were measured at room temperature by the current-in-plane tunneling (CIPT) method from a lithographically unpatterned PMTJ sample and 138% and 6.4 kΩ μm² were obtained, respectively. A PMTJ test pattern, with a junction size of 80 × 40 μm², was also fabricated and showed a MR ratio and RA product of 108% and 4 ∼ 6 kΩ μm², respectively, in good agreement with the CIPT measurements.