Method to Improve the Reliability and Cooling Capability of Thin-Film Magnetoresistive Sensors
Original Publication Date: 2002-Feb-14
Included in the Prior Art Database: 2003-Jun-21
Disclosed is a method to improve the reliability and cooling capability of magnetoresistive (MR) read sensors in magnetic recording heads. To achieve high areal densities, magnetic recording heads require read gap layers with thickness of the order of 100A to separate the thin-film sensors from the magnetic shields. In a conventional recording head, the current-in-plane (CIP) configuration is used where the read sensor is electrically insulated from the shields using dielectric films. Sensor bias current is therefore confined to the sensor and lead, and no appreciable amount of current flows in the shields. During recording head manufacturing processes or during field usage, electric fields in excess of dielectric breakdown point can be developed, damaging the dielectric films and hence rendering the device unusable. Another problem with the conventional CIP configuration arises from the fact that the thickness of electrical leads in contact with the sensor is limited in order to minimize edge-breakdown and adjacent track reading. This will impede cooling of the sensor since heat conduction along the leads is a major mechanism by which heat generated in MR sensors is removed. The present invention alleviates the aforementioned problems by implementing a hybrid CIP (current-in-plane) CPP (current-perpendicular-to-plane) configuration illustrated in Figure 1. The metallic gap is placed in close promixity to the track edges and serves as an electrical conduit that links the shield to the spin valve sensor. The preferred embodiment aligns the sensor track edge with respect to the inner edge of the metallic gap either using self-aligned processes or using high-overlay-accuracy lithography techniques. Fig.1 Thin-fim magnetoresistive (or spin valve) sensor incorporating the metallic gap. By electrically connecting the sensor and the shields the present scheme reduces charge accumulation/electric-field buildup, which is one of the major root causes of electro-static discharge and related electric overstress phenomena. The present scheme also improves sensor cooling by promoting heat conduction away from the sensor to the shields, which serve as a heat sink. Heat conduction through the metallic gap layers is much more effective than heat conduction across the dielectric gap layers. Figure 2 illustrates the possible thermal benefit of the present invention. For sensors with a track width of 100 nm, an AlOx gap of 100A, and a lead sheet resistance of 2 Ohm/sq, as much as 35 percent reduction in peak temperature rise is predicted. The present scheme also reduces the overall lead resistance, which does not contribute to magnetoresistance, and thereby enhances the effective sensitivity of the read sensors.