Improved performance of Cu-Co CPP GMR sensors

We have fabricated and tested GMR magnetic sensors that operate in the CPP mode. This work is a continuation of the ultra-high density magnetic sensor research introduced at INTERMAG 96. We have made two significant modifications to the process sequence. First, contact to the sensor is made through a metal conduit deposited in situ with the multilayers. This deposition replaces electroplating. This configuration ensures a good electrical interface between the top of multilayer stack and the top contact, and a continuous, conductive current path to the sensor. The consequences of this modification are an increase in yield of operational devices to ⩾90% per wafer and a significant reduction of the device resistance to ⩽560 mΩ and of the uniformity of the device resistance to ⩽3%. Second, the as-deposited multilayer structure has been changed from [Cu 30 Å/Co 20 Å]₁₈ (third peak) to [Cu 20.5 Å/Co 12 Å]₃₀ (second peak) to increase the GMR response. The best second peak CPP GMR response from a single device is 39%. The sensitivity of that device is 0.13 %/Oe