Dissolution mechanism of MgO thin film shielding layer in tunneling magnetoresistance hard disk drive read head

[Display omitted] Magnesium oxide (MgO) thin films are used as magnetic shields and barriers for magnetic tunneling junctions in magnetic data storage devices. During the fabrication process, these films are exposed to water, causing a hydration reaction resulting in magnesium hydroxide precipitation. This hydration process can cause material loss and changes in the properties of the films, which may compromise the device performance. In this study, we investigate the dissolution of MgO thin films in deionized water. The magnitude and extent of the damage to the surface structures of the MgO films depend on the properties of the thin films and the time of dissolution. The surface roughness and morphology of the dissolved area are investigated by using atomic force microscopy and scanning electron microscope, respectively. It was found that the surface roughness increased with exposure time to water (from 1 to 10 h), corresponding to increasing film damage. Moreover, a model describing the reaction rate is created based on electrical conductivity measurements of dissolved MgO as a function of time.