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Publications (7)7.11 Total impact

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    ABSTRACT: As the areal density of magnetic recording increases well beyond 100 Gb/in<sup>2</sup>, the critical dimensions of recording heads continue to shrink at a rate of 15%-30% per year. Read sensors with 100 nm physical read widths are being routinely fabricated using undercut resist images and solvent-based liftoff processes. However, because standard liftoff processes using undercut photoresist images have reached their limits and cannot be performed reliably below 100 nm, sensor stabilization with a hard magnet contiguous junction is compromised because of induced variations in junction profile and hard magnet geometry. Furthermore, poor liftoff can induce fencing and excessive read gap topography leading to side reading and poor sensor performance. An alternative sensor patterning approach is proposed based on chemical mechanical polishing (CMP) and no-undercut resist images to define the read sensors critical dimensions. Ultra-narrow giant magnetoresistive (GMR) read heads have been successfully fabricated with physical read widths in the 20-80 nm range and using various sensor designs: Current in-plane (CIP) GMR, current perpendicular to the plane (CPP) GMR, and CPP tunnel magnetoresistive (CPP-TMR) sensors
    IEEE Transactions on Magnetics 11/2006; · 1.42 Impact Factor
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    ABSTRACT: The in-stack stabilization of unshielded and shielded magnetic tunnel junction (MTJ) sensors have been studied experimentally by quasi-static and recording tests as well as theoretically by micromagnetic modeling. Results showed the viability of in-stack stabilization over a range of design and material conditions. Performance tradeoff studies and design optimization results led to the fabrication of MTJ read heads with good magnetic stability and high readback sensitivity.
    IEEE Transactions on Magnetics 02/2004; · 1.42 Impact Factor
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    ABSTRACT: Magnetic recording areal densities using magnetoresistive (MR) head technology are increasing at annual rates in excess of 60% per year and in some applications as great as 100% per year. Today, the critical features of the thin-film head can be patterned with the same optical lithography techniques used by the semiconductor industry. However, with the assumption that areal density increases in magnetic recording are maintained, within the next rive years, thin-film head lithography requirements will exceed semiconductor roadmap projections. This paper describes the use of e-beam lithography as an alternative to optical lithography for the fabrication of critical features in the thin-film head. In particular, the unique geometry of the head structure, the low density of critical head features on the wafer, and the relatively low wafer volume requirements for thin-film heads allow e-beam lithography to become a viable manufacturing alternative for thin-film head fabrication. More important, e-beam lithography is ideally suited for producing thin-film head structures at a development level prior to the optimization of manufacturable optical processing.
    IEEE Transactions on Magnetics 02/2002; · 1.42 Impact Factor
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    ABSTRACT: Magnetic head fabrication for 100 Gbit/in. 2 areal density requires minimum lithographic feature size 0.15 m, with aspect ratios of 8:1–10:1. Electron-beam lithography can provide adequate resolution for research and development of magnetic heads, and at 100 kV can provide greater than 10:1 aspect ratios in 1–3 m thick single-layer resist polymethylmethacrylate. Poly methylmethacrylate PMMA is well known for withstanding the rigors of plating baths, but at these thicknesses requires a nonswelling, low-stress developer such as the LIGA mixture also known as ''GG Developer U.S. Patent No. 4,393,129''. In this work we present the results of isopropyl alcohol:water development for thick PMMA, and describe the dependence of resist contrast on the temperature of the developer. We also demonstrate the advantage of ultrasonic agitation during development. These development techniques have brought resist profiles in PMMA to the theoretical limit predicted by Monte Carlo simulations. © 2002 American Vacuum Society.
    Journal of Vacuum Science & Technology B Microelectronics and Nanometer Structures 01/2002; 20. · 1.36 Impact Factor
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    ABSTRACT: Self-heating of GMR sensors is investigated experimentally and numerically. We measure the thermal conductivity of the read gap layers independently and model heat transfer at the air bearing surface using the results of molecular scale simulations. Temperature profiles obtained by simultaneous application of scanning probe and electrical resistance thermometry agree well with numerical simulation results
    IEEE Transactions on Magnetics 08/2001; · 1.42 Impact Factor
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    ABSTRACT: First Page of the Article
    Magnetics Conference, 1999. Digest of INTERMAG 99. 1999 IEEE International; 06/1999
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    ABSTRACT: We have successfully demonstrated magnetic recording at areal densities as high as 12 Gb/in<sup>2</sup> at a data rate of 14~15 MB/s using separate spin-valve read heads and narrow pole-tip inductive write heads on low noise Co alloy thin film disks. In this work, the nominal target densities were 350 Kbpi×34 Ktpi. To make these densities possible, large signal-to-noise gains were attained with the use of high performance spin-valve read heads and low noise thin film media. At the same time, very narrow track write heads were designed and fabricated by extending conventional photolithographic techniques. Finally, small magnetic spacings between the head and the disk were attained with low flying ABS designs and improved head and disk surfaces. Recording tests showed satisfactory writability and large readback signal of around 2 mV/μm. The 50% rolloff densities were as high as 10 Kfc/mm, while the write and read trackwidths were as narrow as 0.7 and 0.5 μm respectively. An overall assessment of the parametric recording results indicated an areal density capability of at least 10 Gb/in<sup>2</sup>. This projection was confirmed by error rate testing with an EPR-4 channel, where very low ontrack errors of 10<sup>-10</sup>~10<sup>-9 </sup> were achieved at 315~380 Kbpi. Furthermore, squeeze measurements revealed well-defined 747 behavior with offtrack maxima at 0.7~0.8 μm trackpitch. The product of linear and track densities for the write and read head combinations tested indeed showed that an areal density of 11~12 Gb/in<sup>2</sup> has been achieved
    IEEE Transactions on Magnetics 04/1999; · 1.42 Impact Factor