Proceedings PaperDesign and fabrication of high performance spintronic sensors (Conference Presentation)
In this work, a concise method is described for providing multi-axis pinning and used to fabricate two-axis GMR sensors on one wafer. Firstly, a thin film stack with structure of 2Ta/3Ru/7IrMn80/2CoFe10/0.85Ru/2.1CoFe10/1.9Cu/1.2CoFe10/2.5NiFe19/4Ta (layer thickness in nm) is deposited on SiO2 substrate. Then the fabrication process is performed on as-deposited film by three steps of lithography based on a special layout including a full-Wheatstone-bridge sensor and a half-bridge sensor. The patterned devices are annealed in vacuum under a magnetic field of 0.9T along X-axis for 1h, then a field of -80mT for a few minutes before cooling down to room temperature. Through this design, the half-bridge sensor is sensitive to the field in X-axis while the full-bridge one responses only to the field in Y-axis with good performance. The fabrication method is cost-efficient and highly interesting for industrial mass-production. Then a perpendicular TMR sensor is demonstrated using MTJs wih in-plane magnetized free layer and a perpendicularly magnetized reference layer. we studied the free layer CoFeB thickness dependence of tunneling magnetoresistance (TMR) ratio and resistance-area product (RA) in this kind of MTJ. An optimal thickness of free layer to achieve linear response is found.