Thermal stability characterization of tunneling magneto resistive structure for data storage applications

Abstract

The conventional read sensor technology used in hard disk drives is the tunneling magneto resistive (TMR) device. The revolutions of technology have been developed to achieve high performance of reading signal resulting in very thin and complicated device layers which thermal induced degradation and defects would be concerned. In this research, a thermal stress has been applied to TMR devices between 150-250 ℃ for reliability investigation. The resistance, amplitude and asymmetry parameters, before and after the thermal stress, were measured using a quasi-static tester (QST). The results showed the temperature dependence of the percentage change in QST resistance, asymmetry and amplitude. The microstructure of the annealed devices was observed using TEM, STEM and XEDS. It was found that structural defects that can be related to the QST parametric changes. Both atomic misalignment of MgO layer and Mn depletion can lead to instability of the magnetic response of TMR after be stressed at high temperature. The in-situ real-time annealing STEM showed a sign of Ru interface change at 350 oC which lower atomic weight elements can diffuse to adjacent layers. The laser stress results exhibit amplitude degradation without changing in resistance and asymmetry. STEM and XEDS analysis indicate portion of Mn depletion in antiferromagnetic layer.