By Mike Watts
There were many papers at SPIE Advanced Lithography on Bit Patterned Media (BPM), potentially the way that 1 Tera bit per square inch (1 Tb/in²) hard disk drives will be made in the near future. I think BPM will be the next volume manufacturing application for imprint. Today, roll to roll optical products and wafer level lenses for cell phone cameras are the volume applications.
The speakers described how hard drives at 0.3 Tb/in² can be made with current technology, and may just make it to 0.6 Tb/in². Heat Assisted Magnetic Recording (HAMR) may allow 1 doubling of density by changing the head design. HAMR works much as it sounds, the magnetic material is locally heated just before writing a bit, which results in sufficient material stability at room temperature for reliable long term data storage. There is no need to make a fundamental change to the disk design to implement HAMR which make it attractive in the short term.
After possibly 1 generation of HAMR , it seems that BPM will be essential for products from 1-10 Tb/in². Volume manufacturing by 2013 was possible, more likely 2015, seemed to be the consensus. Seagate showed patterning results at 1 Tb/in², and the author seemed disappointed that they had not been able to show read/write data at 1 Tb/in², and but did show results for 0.3 Tb/in². It was clear that a full functional demonstration at the insertion density was imminent.
The lithographic challenges are daunting and are significantly ahead of the semiconductor road map. At 1 Tb/in², features at 15 nm half pitch must resolved. At 10 Tb/in², 4 nm half pitch is required. These must be achieved double sided with position and size control of 15 % 3 sigma, defect density of 10-4 and at a cost of less than $1 a disk.
Both Seagate and Hitachi Global Storage Technologies also showed all sorts of detailed process results using very similar strategies. The masters are made on a special rotary stage e- beam machine. They are written at one-fourth the target density. They then use guided self assembly of a block copolymer to quadruple the density of the spots.
About the Author
Mike Watts has been patterning since 1 um was the critical barrier, in other words for a longtime. I am a tall limey who is failing to develop a Texas accent here in Austin. I have a consulting shingle at www.impattern.com.
²My blog “ImPattering” will focus on the latest developments in the business and technology of patterning. I am particularly interested in trying to identify how the latest commercial applications evolve.