HDDs: terabyte/in2 a near-term reality
09/01/2008
Patterned media technology on hard disk drives??? made possible by new lithographic processes with unprecedented levels of resolution, pattern precision, and cost of efficiency???overcomes limitations of superparamagnetic effects inherent in conventional technology. This is expected to make storage densities exceeding 1012 bits per square inch (1 Terabyte/in2) possible in the near future.
This issue of Data Storage (a supplement to Solid State Technology) looks at several different aspects of lithography for HDDs. First, Molecular Imprints and Seagate team up to provide a look at step and flash imprint lithography for patterned media. Next, Hitachi and the University of Wisconsin describe the manufacture of master templates for printing fine-pitch bit patterns using e-beam lithography and copolymer self-assembly. Obducat provides another perspective on the use of electron beam and nanoimprint lithography for patterned media. I think you’ll find them both informative and useful so enjoy!
HDD lithography will also be a highlight of this month’s DISKCON conference, to be held Sept. 15-18 at the Hyatt Regency Hotel/Santa Clara Convention Center in California. A special session will address all aspects of lithography; from the present UV exposure tool capability and its future enhancements, to e-beam mastering and nano-imprinting.
The chairman of the session is Paul Hofemann, VP of HDD and Emerging Markets Business Development, Molecular Imprints, Inc. He notes the similarities and differences between the requirements for the HDD and semiconductor industries. “Critical dimensions for both thin-film heads and semiconductors have been shrinking at an accelerated rate. Up to this point, both industries have been continually utilizing more expensive exposure tools and increasingly complex lithographic processes. Yet, the resolution and cost challenges of the hard disk drive industry are, in many ways, more challenging than those in the semiconductor industry,” Hofemann notes.
“For instance, to maintain ~50% per year growth in areal density to well beyond 1TB/in2 will require the introduction of patterned media into the HDD technology roadmap. The formidable cost challenges in the HDD industry also necessitate adoption of a novel lithography technology and accelerating critical dimension reductions even faster than NAND flash. Existing approaches developed for semiconductor companies to meet advanced resolution requirements are simply incompatible on a cost and throughput basis with the HDD industry’s roadmap. This talk will focus on both the industry’s challenges and a new lithography strategy to keep the HDD industry on the roadmap,” according to Hofemann.
Robert Fontana, Jr. and Steven Hetzler of IBM will also be presenting at the DISKCON session. They note that magnetic recording hard disk drive technology and solid state storage technology, most notably NAND flash, have product goals to increase device capacity, i.e. areal density, by 40% annually. “YE2007 disk products, a 250GB capacity 2.5in. diameter disk with two surfaces, had areal densities of 200 GB/in?? using minimum lithographic patterning for the MR transducer of 75nm. YE2007 NAND flash devices, a 2GB capacity 6mm ?? 24mm chip, had areal densities of 83GB/in?? using minimum lithographic patterning for bit line equal line and spaces of 54nm in a 2bit/cell design,” they write in an advance abstract.
These IBMers will examine the prospects of both technologies’ ability to sustain 40% areal density increases by identifying the critical device structures for these storage technologies and then by comparing the minimum feature processing requirements these structures must achieve over the next 5 years with the lithographic projections published by the International Technology Roadmap for Semiconductors (ITRS). “Simply stated, in the 2012 time frame, areal density goals of ~1TB/in?? for magnetic recording and ~ 400GB/in?? for MLC NAND flash will be limited by projected semiconductor minimum feature processing of 28nm and alignment or overlay control of 5.6nm,” they state.
Ren Xu, key account technologist at Intevac, says that higher density recording beyond 1TB/in2 in the HDD business requires new recording schemes and media process approaches a typical manufacturing line has not seen before. “Included are higher temperature process capability for HAMR, off-line nanoimprinting, in-vacuum resist and other sacrificial layer trim and strip for BPM and DTR, in-vacuum patterning, exotic lubricant and corresponding new ways of applying them to the finished disk surfaces, etc. just to name a few,” he said. Sounds like the making of a future supplement to me!
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Peter Singer
Editor-in-Chief