Perpendicular Magnetic Recording

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 400 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 2013.

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.  So, ultimately PMR recording will run into the thermal stability limit as was the case with LMR.

“Planar” PMR disks consist of a stack of thin layers deposited sequentially across the entire disk surface in a vacuum system, each of which performs a specific function to insure a vertical orientation of the media; thus, the axis of magnetization is perpendicular to the plane of the film. Advances in PMR have been achieved by continuously reducing dimensions in the head/media space, such as head geometry, media grain size, head-media spacing, and other dimensions.

The sputtering technology used in Intevac’s 200 Lean^® is the industry standard for depositing complex multi-layer PMR film structures. It’s proprietary , high throughput cathode (target) designs have enabled continuous increases in productivity, reducing manufacturing costs even as new, high-density HDD designs are introduced. Figure 2  shows the layering structure of today’s second-generation PMR; to enable next-generation PMR as well as future media designs, the 10 sputtered layers shown here, plus the need for heating and sputter-etching, will require expansion of existing tools by the addition of more process chambers to allow for deposition of at least 13 individual layers.  The 200 Lean system can accommodate up to 24 process chambers  without impacting the footprint significantly.