High yield Cu-Co CPP GMR multilayer sensors

We have fabricated and tested GMR magnetic flux 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 {ge}90% per wafer and a significant reduction of the device resistance to {le}560 milliohms and of the uniformity of the device resistance to {le}3%. Second, the as-deposited multilayer structure has been changed from [Cu 30 {angstrom}/Co 20 {angstrom}]{sub 18} (third peak) to [Cu 20.5 {angstrom}/Co 12 {angstrom}]{sub 30} (second peak) to increase the CPP and CIP responses. The sheet film second peak CIP GMR response is 18% and the sensitivity is 0.08 %/Oe. The sheet film third peak CIP GMR response is 8% and the sensitivity is 0. 05 %/Oe. The second peak CPP GMR response averaged over twenty devices on a four inch silicon substrate is 28% {+-} 6%. The response decreases radially from the substrate center. The average response at the center of the substrate is 33% {+-} 4%. The average second peak CPP sensitivity is 0.09 %/Oe {+-} 0.02 %/Oe. The best second peak CPP response from a single device is 39%. The sensitivity of that device is 0.13 %/Oe. The third peak CPP GMR response is approximately 14 %. The third peak CPP response sensitivity is 0.07 %/Oe. 6 refs., 3 figs

Temperature dependence and mechanisms for vortex pinning by periodic arrays of Ni dots in Nb films

Pinning interactions between superconducting vortices in Nb and magnetic Ni dots were studied as a function of current and temperature to clarify the nature of pinning mechanisms. A strong current dependence is found for a square array of dots, with a temperature dependent optimum current for the observation of periodic pinning, that decreases with temperature as (1-T/Tc)3/2. This same temperature dependence is found for the critical current at the first matching field with a rectangular array of dots. The analysis of these results allows to narrow the possible pinning mechanisms to a combination of two: the interaction between the vortex and the magnetic moment of the dot and the proximity effect. Moreover, for the rectangular dot array, the temperature dependence of the crossover between the low field regime with a rectangular vortex lattice to the high field regime with a square configuration has been studied. It is found that the crossover field increases with decreasing temperature. This dependence indicates a change in the balance between elastic and pinning energies, associated with dynamical effects of the vortex lattice in the high field range.Comment: 12 text pages (revtex), 6 figures (1st jpeg, 2nd-6th postscript) accepted in Physical Review

Perpendicular giant magnetoresistance in a 0.4 {mu}m diameter multilayer sensor

We have fabricated a novel GMR ML flux sensor that is designed to operate in the CPP mode. The GMR sensor is a 0.4 {mu}m diameter, 0.09 {mu}m high Cu-Co ML pedestal. The sensors are patterned using electron beam lithography. The Al{sub 2}O{sub 3}-TiC substrate is coated with a sputter deposited Al{sub 2}O{sub 3} film that is polished to <0.2 nm RMS roughness. Contact to the bottom of the GMR sensor is made by depositing the Cu-Co multilayers onto a smooth 0.45 {mu}m thick Mo-Si ML stack. The top contact is self-aligned to the GMR sensor. This is accomplished, in part, by CMP. The top and bottom contact layers are electrically isolated by a PECVD Si{sub 3}N{sub 4} film. The configuration of the contacts allows four point probe resistance measurements. The GMR response of these 0.4 {mu}m diameter sensors is 12%

A manufacturable miniature electron beam column

A new and manufacturable miniature electron beam column has been designed, fabricated and tested. The low-voltage, all electrostatic, microfabricated electron beam column includes lenses consisting of bonded stacks of micro-machined silicon and glass. The lenses are microfabricated on 150 mm diameter substrates using semiconductor and bulk micro-machining fabrication processes. These processes are capable of fabricating columns with precise aperture diameters, and repeatable alignment tolerances. They also enable new designs that significantly increase the voltages at which miniature columns can reliably operate. The lenses are assembled onto a ceramic package using pick-and-place production tools. The package is fabricated using technologies that allow interconnects to be strategically distributed and encapsulated using high-resolution pattern transfer and enable fabricating small packages with high density routing and easy integration of buried and external passive and active devices, ground planes, and controlled impedance lines. Beam characterization of the column has begun and optimization continues. Preliminary spot size and resolution are presented