Electromigration-induced failure of single layered NiFe Permalloy thin films for a giant magnetoresistive read head

Abstract

Electromigration-induced failures have been investigated in single layered NiFe Permalloy thin films, which are used in giant magnetoresistance (GMR) read heads in high-density magnetic recording disk drives. The time-to-failure and median-time-to-failure (MTTF, t50) of NiFe thin films were found to be strongly dependent on the applied current density, film thickness, and ambient temperature. The activation energy (ΔQ) of NiFe films derived from the “Black equation” was found to be 0.8 eV. The MTTF and standard deviation (σ) of a NiFe thin film electromigration test stripe with 10 nm thickness, 5 μm width, and 20 μm length were 3.74 and 1.74 h, respectively, at 160 °C ambient temperature. Typical electromigration failures such as “voids and cracks” were observed at the cathode or center region of NiFe film test stripes. These results suggest that the electromigration-induced failures are one of the crucial factors in determining the reliability of GMR spin-valve read heads used in high-density magnetic recording disk drives.