Storage density and storage capacity in the hard disk drive industry have long been driven by areal density growth. Currently, HDDs are available with areal densities greater than 700 Gb/in², utilizing perpendicular magnetic recording (PMR) technology. The practical limit of conventional PMR could be as high as 1.5 Tb/in²; drives with this density could be in production by 2015.
The key difference of PMR vs. earlier longitudinal recording (LMR) is that the grain structure and the magnetic orientation of the stored data of PMR media is columnar instead of longitudinal. PMR’s advantages include improved thermal stability, improved signal-to-noise ratio (SNR) due to better grain separation and uniformity, and better writability due to stronger head fields and better magnetic alignment of the media. PMR’s fundamental limitations involve the thermal stability of magnetically written bits of data and the need to have sufficient SNR to read back written information. Ultimately PMR recording, like LMR, will reach its thermal stability limit.
“Planar” PMR disks consist of a stack of thin layers deposited sequentially across the entire disk surface in a vacuum system. Each layer performs a specific function to ensure a vertical media orientation and that the axis of magnetization is perpendicular to the plane of the film. PMR technology advances have been achieved by continuously reducing head/media space dimensions including head geometry, media grain size, head-media spacing, and other dimensions.
Intevac’s 200 Lean sputtering technology is the industry standard for depositing complex multi-layer PMR film structures. Our proprietary, high-throughput cathode (target) designs continuously increase productivity and reduce manufacturing costs, even as new, high-density HDD designs are introduced.
The above graph demonstrates the layering structure of today’s second-generation PMR, next-generation PMR, and future media designs. With ten sputtered layers and the need for heating and sputter-etching will require existing tools to add process chambers to increase deposition capabilities of at least 13 individual layers. The 200 Lean can accommodate up to 28 process chambers without impacting the footprint significantly.