Patterned media technologies involve a photolithographic patterning of the recording media. Patterning allows the servo pattern that controls head placement during operation to be physically pre-printed on each disk, reducing drive manufacturing costs. Traditionally, the magnetic servo pattern in a drive has to be recorded on the disks in that drive after the drive is assembled. Each data location will contain a single bit and provide isolation of each bit that reduces read-back noise thereby increasing SNR and storage density.
A key challenge to the production of patterned media will be to fabricate sub-20nm features on the entire media surface, with very close tolerances and tightly controlled magnetic properties. Today, only electron beam lithography can produce imprint masters with these dimensions. This is the first time that the lithography required to support the HDD roadmap will be finer than that supporting the semiconductor device roadmap.
MANUFACTURING PROCESS FLOW
Patterned media fabrication begins with a master resist pattern produced using electron-beam lithography on a silicon wafer. This master is then used to produce hundreds to thousands of imprint stamps followed by low-cost nano-imprint lithography that transfers the pattern onto the magnetic disk surface. There are two methods to pattern disks:
- Pattern the substrate before deposition of the magnetic film structure
- Pattern the media after the magnetic layers have been deposited
The film thicknesses required for perpendicular make the second approach more practical and the method of choice. The pattern is then developed by ultra-violet (UV) curing and the magnetic islands – or tracks – are formed by etching the stamped resist pattern into the magnetic film. A non-magnetic material is then deposited into the subtracted areas and the media surface is planarized to help with head flyability over the media. Finally, the patterned, planarized disk will need a protective overcoat, lubrication and final test.
RISING TO THE CHALLENGE
Intevac’s core sputtering technology is already being extended by leading HDD companies for patterned media development and commercialization. Moving from today’s second-generation of PMR media to nano-patterned media will involve more layers of ultra-thin films with new alloys, thinner and denser carbon structures, improved lubrication materials and lower defects. Nano-patterned media will necessitate more process stations in the critical sputtering tools. To enable next-generation patterned media designs, the 10 sputtered layers typically needed today, plus the need for heating and sputter-etching, will require tools with more sputtering stations. The 200 Lean system can handle up to 28 vacuum stations in a small footprint configuration, making it ideal for patterned media fabrication. The modular nature of the 200 Lean platform allows the development of a fully integrated, continuous media patterning and planarization process. Our patented Halo etch source can effectively etch cured photoresist as well as metal layers to fully define any particular pattern across the entire surface of the disk. Additional chambers are used for the pattern fill and etch back processes necessary to planarize the finished disk surface as well as deposit the final protective overcoat. The result is the production of fully patterned disks at throughput rates that are comparable to those achieved with planar media. This presents a significant manufacturing advantage for implementation of patterned media technology.