Nano Processing Strategies for MR Sensor Read Width and Stripe Height Formation

As the areal density of magnetic recording increases well beyond 100 Gb/in
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, 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.