Development of atomic-scale thin-film deposition system for perpendicular magnetic tunnel junctions with high tunneling magnetoresistance

The advancement of magnetic random access memory (MRAM) benefits from academic research on magnetic tunnel junctions (MTJs). However, deposition systems for academic research are often limited by atomic-scale control, process automation, and post-deposition processing, resulting in suboptimal tunneling magnetoresistance (TMR) ratios. We developed a deposition system optimized for perpendicular MTJ (p-MTJ) deposition, addressing key limitations in atomic-scale deposition, automation, and process control. Optimizations in critical components such as the cathode, sample manipulator, and automated deposition software were implemented. A dedicated process control chamber for post-annealing was introduced to enhance perpendicular magnetic anisotropy (PMA) and TMR. Experimental characterization confirmed that the deposited films exhibited low interfacial roughness (the average roughness (Ra) of MgO <0.35 nm, other materials' Ra < 0.25 nm). The CoFeB/MgO multilayers achieved wide-range PMA through CoFeB thicknesses from 0.7 to 1.1 nm in 0.1-nm steps, confirming atomic-scale deposition resolution and superior interface quality. Through fine-tuning, the full-stack p-MTJ achieved a TMR of 135%, validating the precise control capability of our system over TMR modulation. This system offers a more efficient platform for MRAM research and further innovation.