Hard Drive Progress Report

In June, I heard from HGST that very nice progress on Bit Patterned Media (BPM) would be reported in August. At The Magnetic Recording Conference (TMRC) meeting in August, the HGST team presented four papers on aspects of their Bit Patterned Media program. Their progress was definitely nice!

The bottom line was shown in a poster with record-breaking BPM read and write at 1.6 Tdot per square inch (roughly equivalent to 1.3 Tbit per square inch, once typical coding overhead is accounted for). This is not only a record, but also the critical density for next-generation insertion, so it represents a very significant milestone. Even better, the read and write signal quality appeared to be good enough to match what is needed in a typical hard drive.

The HGST presenters were quick to point out, however, that they are not yet close to production. The test was done on a static tester or “drag tester”, rather than testing a spinning disk. In their experience, drag test data is a good predictor of what a spin stand test will show and these results are consistent with previous data at lower density. An obvious next step is to add suitable coding and servo to the pattern and do the spin stand test. Other next steps include uniform patterning over a whole disk; these results were obtained on a patterned ring covering about 1/3 of the disk. Also patterning uniformity within the ring needs improvement. It’s worth noting that because of all the error correcting capability in modern disks, the target defect density is modest, at 1 per 1000.

The other papers described different process solutions that have enabled this demonstration. They described more patterning heroics in the creation of the master pattern. Perhaps the most intriguing was an alternative to etch to create the island magnetic bits. They showed results from patterning the substrate, and epitaxial “templated growth” of the magnetic material on the tops of the islands.

My takeaway from the announcement was that the race to greater than 1 Tbit drives is alive and well, with this demonstration of target device performance for BPM. Improving device area and defect density is now the key barrier, which is something that the semiconductor industry has done many times. There is no question that these are well-funded programs, and the finish line is within sight!