Abstract:
A method for making a current-perpendicular-to-the-plane magnetoresistive sensor structure produces a top electrode that is “self-aligned” on the top of the sensor and with a width less than the sensor trackwidth. A pair of walls of ion-milling resistant material are fabricated to a predetermined height above the biasing layers at the sensor side edges. A layer of electrode material is then deposited onto the top of the sensor between the two walls. The walls serve as a mask during angled ion milling to remove outer portions of the electrode layer. The height of the walls and the angle of ion milling determines the width of the resulting top electrode. This leaves the reduced-width top electrode located on the sensor. Because of the directional ion milling using walls that are aligned with the sensor side edges, the reduced-width top electrode is self-aligned in the center of the sensor.
Abstract:
A current-perpendicular-to-the plane magnetoresistive sensor has top and bottom electrodes narrower than the sensor trackwidth. The electrodes are formed of one of Cu, Au, Ag and AgSn, which have an ion milling etch rate much higher than the etch rates for the sensor's ferromagnetic materials. Ion milling is performed at a high angle relative to a line orthogonal to the plane of the electrode layers and the layers in the sensor stack. Because of the much higher etch rate of the material of the top and bottom electrode layers, the electrode layers will have side edges that are recessed from the side edges of the free layer. This reduces the surface areas for the top and bottom electrodes, which causes the sense current passing through the sensor's free layer to be confined in a narrower channel, which is equivalent to having a sensor with narrower physical trackwidth.