Thermal Stress Evaluation of Tunneling Magnetoresistive Structures in Data Storage Devices

The conventional read sensor technology used in hard disk drives is the tunneling magnetoresistive (TMR) device. The technology evolution of the TMR device toward higher signal-to-noise performance has been achieved through aggressive scaling of the thin film layered structures in the device to the point that thermal stability and thermally induced degradation have come to limit reliability. In this study, a thermal stress has been applied to TMR devices between 150–250 °C, and the resistance, amplitude, and asymmetry parameters, both before and after the thermal stress, were measured using a quasi-static test (QST). The results reveal a temperature dependence of the TMR device performance. The microstructure of the annealed devices was further studied using transmission electron microscopy and energy dispersive X-ray analysis, revealing structural defects that are related to the QST parametric changes. Both atomic misalignment of the MgO layer and Ir depletion are proposed as origins for the instability of the magnetic response in the device after thermal stress.