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Opinion: HDDs need patterned media boost

Posted: 16 Sep 2009 ?? ?Print Version ?Bookmark and Share

Keywords:HDD? disk drive? HDD roadmap? patterned media?

Technology roadmaps are the lifeblood of most electronics industries. The International Technology Roadmap for Semiconductors (ITRS) has been an invaluable tool to align R&D and product development activities across the $200 billion IC industry, which requires close process integration for timely generational products. This semiconductor roadmap is periodically updated by many industry experts who also provide advance warning of pending technology limitations, potential solutions, and areas requiring innovation.

The HDD industry also finds its lifeblood in a technology roadmap. The areal density roadmap describes the number of magnetic bits per unit area on the disk platterthereby defining the storage capacity. Each year the areal density increases by an average of 40 percent, enabling disk drives to play the lead role in serving humankind's insatiable thirst for reliable, compact and economical data storage. During the first half of this decade most areal density advances have been the result of changes to the thin-film head (TFH) that allow it to read and write smaller bits of data as it flies at an altitude of less than 10nm above a magnetic disk platter rotating at a typical 7,500 rpm. In more recent years, areal density improvements have been attributed to changing the magnetic bits on the disk platter from a longitudinal to a more compact perpendicular orientation.

Perpendicular magnetic recording (PMR) technology and TFH advances have enabled today's state of the art areal density of over 400Gbit/in?. The leading 'magneticians' believe PMR can be extended to close to 1,000Gbit/in? or 1Tbit/in?. This will be an impressive feat, but by the end of 2011 the industry's areal density roadmap will require 1.2Tbit/in?. While the HDD industry is accustomed to having only a two- or three-year solution horizon, crossing the 1Tbit/in? technology barrier will not be business as usual.

The prevailing plan to avoid a cardiac arrest of the areal density roadmap involves patterning of the hard disk platters. A patterned media surface physically defines the geometric shape and placement of each bit on the disk. This feature isolation improves the signal-to-noise during the normal read/write operations of the hard drive and enables further bit shrinks otherwise unpractical due to data loss from exceeding the infamous superparamagnetic limit. (This occurs when bits become too small and their states randomly flip from thermal instability even at normal ambient temperatures.)

Patterned media challenge
Incorporating patterned disk media into future hard drives will require the adoption of novel process technologies for nanoscale patterning that have never seen high-volume manufacturing. For the first time, HDD resolution requirements will leapfrog the ITRS roadmap, thereby eliminating any prospects of borrowing semiconductor lithography equipment. Double-sided etch of magnetic film stacks with variable pattern densities and subsequent single nanometer planarization must be accomplished at production line speeds averaging 1,000 disks per hour. With inflexible frugality, the consolidated costs of all the new patterning steps must not add more than one or two dollars to today's five-dollar disk.

Fortunately, it appears the industry is well on its way to rising to the patterned media challenge. The keystone of these new enabling technologies is Jet and Flash Imprint Lithography (J-FIL), which can provide less than 20nm feature resolution and is an order of magnitude less expensive than the leading 193nm optical techniques. J-FIL imprint systems have been widely adopted over the past several years by HDD companies developing patterned media products.

It goes without saying that crossing the 1Tbit/in? areal density threshold by 2011 requires significant investment from the HDD manufacturers and the supporting supply chain. Traditionally, each HDD manufacturer pursues a competitive advantage from a customized manufacturing process. This time it will be difficult for this relatively small $28 billion HDD industry to fund multiple patterned media solutions. Subtle equipment tailoring will exist, but the biggest advantages will be born from less tangible differentiators. Key among these is:

??Be first to market and have the ability to ramp at the lowest cost. Successful HDD manufacturers must emphasize early yield learning and seamless integration of pilot-line equipment, not research tools masquerading as manufacturing equipment.
??Involve OEM suppliers early in product development cycles. The savviest HDD manufacturers realize that introducing new technologies require recruiting complementary skill sets beyond the resource pool of their competitors. There has never been a better time to find top talent in lithography, etch and yield management to add pattern transfer expertise to their traditional media deposition veterans.

Next year, patterned media will progress from product development to pilot-line manufacturing. This transition will require the adoption of new process technologies such as J-FIL with greater focus on process integration and pilot-line yield learning. While the next several years will not be business as usual, realizing the promise of patterned media will ensure a viable technology roadmap and keep the HDD industry's lifeblood flowing well into the next decade.

- Paul Hofemann
VP, HDD Marketing and Business Development
Molecular Imprints





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