Numerical failure analysis of current-confined-path current perpendicular-to-plane giant magnetoresistance spin-valve read sensors under high current density

摘要

Thermomigration (TM)-induced failures occurred in the current-confined-path (CCP) current perpendicular-to-the plane (CPP) giant magnetoresistance spin valve (GMR SV) read sensors with Cu nanopillar metal paths (~5 nm in diameter) operating at a high current density (J > 2 × 10~7 A/cm~2) have been numerically studied to explore the magnetic and electrical stability. The Cu interdiffusion (migration) from nanopillars into adjacent magnetic layers (e.g., CoFe) due to thermally induced mass transport was found to be the main physical reason for the magnetic failures of CCP-CPP GMR SV read sensors including the change in interlayer coupling and the reduction in exchange bias field as well as MR. Furthermore, it was numerically verified that the TM-induced failures are more dominant than the electromigration-induced failures at the higher current density beyond J = 6 × 10~7 A/cm~2 in the CCP-CPP GMR SV read sensors. However, all the numerical calculation results demonstrated in this study clearly suggest that these undesirable electrical and magnetic failures occurred in the CCP-CPP GMR SV read sensors can be improved by tuning the path density, the purity (electrical resistivity), and the uniformity of Cu nanopillar metal paths.