A collaborative course for HDD manufacturing
P. Hofemann, Molecular Imprints, Austin, TX USA
The hard disk drive (HDD) industry has been evaluating lithographically patterned media as a vehicle to maintain the ∼40% per year growth in areal density, to well beyond 1Tb/in2. To achieve this in a timely manner means reducing critical dimensions even smaller than NAND flash features. At the same time, this must be accomplished at a fraction of the cost associated with traditional optical lithography for semiconductors???driving a parallel need for new imprint lithography technology along with appropriate deposition and etch technologies. The successful implementation of these technologies into high-volume manufacturing requires extraordinary levels of collaboration between hard disk manufacturers, equipment suppliers, and among equipment suppliers themselves. It also requires the development of a Lithography Roadmap for Patterned Media (LRPM).
While much can be learned from the semiconductor industry and its International Technology Roadmap for Semiconductor (ITRS), the challenges facing the HDD industry are unique, and in many ways more daunting.
Experience/history: While some HDD producers utilize traditional optical lithography to produce thin-film heads, none have experience applying lithography to magnetic media. Traditionally, thin-film heads are not produced in the same factories or even in the same countries as media. Introducing lithography to existing, high-volume media factories requires significant clean room expansion and the hiring and training of new engineers and factory workers.
Throughput/volume: Most media production lines operate at 800-1000 disks/hr., in contrast with semiconductor lithography cells, which operate at 100-150wph. Gartner reports that in 2007, the semiconductor industry consumed nearly 80M 300mm wafers, which, according to the SIA, represented some 47% of the total silicon area consumed. Coughlin Associates noted that the HDD industry produced just under 800M magnetic media in 2007, and is forecasted to grow to nearly 1.8B by the time patterned media is in production in 2013.
Cost: Current cost estimates for patterning a single mask layer using 193nm dry lithography at the 45nm node range from $20-25. Patterned media requires patterning on both sides, or the equivalent of two mask layers. HDD producers believe the cost of the entire patterning process???which includes pre-cleaning, double-sided patterning, etching, post-cleaning, and inspection/metrology???must not exceed $1-2/disk.
Substrate Materials: Semiconductor patterning experience is based largely on silicon oxides and nitrides as well as aluminum and copper, whereas HDD producers will be patterning rather exotic thin-film magnetic stacks. In addition, the hole in the center of magnetic media poses unique resist coating challenges.
Achieving resolution, cost, and production requirements for patterned media applications requires intense collaboration between suppliers, and between suppliers and customers. The HDD industry cannot afford very different solutions for each manufacturer. Opportunities for collaboration???including template fabrication and standards, media transportation and automation standards, imprint lithography and etch, inspection, and metrology???identify and close gaps in defect detection and classification.
Over the past few decades, the HDD industry has achieved dramatic increases in areal density and production volumes while holding down costs. Each time, HDD companies faced and successfully overcame daunting challenges. The transition to patterned media creates a whole new set of challenges for the HDD industry???including the introduction of new processes. Through cooperation and collaboration, however, the HDD industry can accelerate the adoption of patterned media and continue on the path toward higher aerial densities.
Paul Hofemann is V.P. of marketing and business development for hard disk drives and emerging markets at Molecular Imprints, 1807 West Braker Lane, Building C-100, Austin TX 78758-3605 USA; ph. 512/339-7760; e-mail: firstname.lastname@example.org.