Perpendicular Magnetic Recording Disk Patterned Servo Regions
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Solution Overview
Problem
Magnetic recording disks with patterned servo regions face challenges in generating an adequate servo signal and maintaining a reliable head-disk interface due to topographical differences between data and servo regions, which can lead to magnetic spacing modulations and performance degradation, especially when using templated growth methods.
Innovation Solution
The implementation of a perpendicular magnetic recording disk with patterned servo regions featuring a seed layer made of non-reactive materials like Pt, Pd, Rh, or Au, and a magnetic recording material comprising Co, Pt, and Cr, with a ruthenium-containing layer, allowing for templated growth that reduces magnetic field differences between servo pillars and trenches through structural and compositional engineering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If templated growth method is used to create patterned servo regions, then manufacturing complexity is reduced, but inadequate servo signal generation occurs due to topographical differences between data and servo regions
Solution Approach 1:
The patent applies local quality by creating distinct structural configurations in different regions of the disk. Data regions feature narrow trenches (5-15 nm) with magnetic material grown thereon, while servo regions feature wider trenches (20-50 nm) with oxide material filling. This localized structural differentiation enables the templated growth method to simultaneously produce appropriate magnetic field contrasts for both data storage and servo functions without requiring separate manufacturing processes.
Solution Approach 2:
The patent utilizes parameter changes by varying the trench width parameter between data and servo regions. By making servo trenches significantly wider than data trenches, the magnetic field distribution is altered to provide adequate servo signal generation. The oxide filling in wider servo trenches creates a non-magnetic region that enhances magnetic field contrast, while the narrower data trenches maintain the required magnetic properties for data storage.
2Reliability
If wide servo trenches are created to generate adequate servo signal, then servo signal quality improves, but topographical variations increase causing magnetic spacing modulations
Solution Approach 1:
The patent introduces an intermediary material (oxide) to fill the wide servo trenches. This oxide filler acts as a mediator that maintains the wide trench geometry necessary for servo signal generation while providing a uniform, non-magnetic surface that reduces topographical variations. The oxide material fills the trenches completely, creating a planarized surface that minimizes magnetic spacing modulations as the read/write head transitions between data and servo regions.
3Reliability
If etching is used to remove magnetic material in servo regions, then adequate magnetic field contrast is achieved, but magnetic material damage occurs
Solution Approach 1:
The patent applies preliminary action by pre-forming the servo trench pattern in the underlayer before depositing the magnetic recording layer. The servo trenches are created in the oxidizable material layer, and then the magnetic material is selectively grown only in data regions using templated growth. This preliminary structuring eliminates the need for subsequent etching of magnetic material in servo regions, thereby avoiding damage to the magnetic layers while still achieving the required magnetic field contrast through selective material deposition.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the generation of an adequate servo signal and improves the reliability of the head-disk interface by reducing magnetic field differences and topographical variations, potentially eliminating the need for expensive planarization processes.
Implementation Method 1
The underlayer is made of an oxidizable material and the seed layer is made of a material substantially non-reactive with oxygen
Implementation Method 2
Magnetic CoPtCr material and nonmagnetic oxide material is then sputter deposited simultaneously
Data Source
AI summary
A perpendicular magnetic recording disk has servo regions that have a patterned underlayer with seed layer pillars formed on the underlayer pillars above the underlayer trenches. The underlayer is made of an oxidizable material. Magnetic recording material is located on the seed layer pillars and on an oxide layer in the underlayer trenches. The magnetic material in the trenches exhibits a magnetic field substantially less than the magnetic field exhibited by the magnetic material on the seed layer pillars, which has perpendicular magnetic anisotropy. The reduced magnetic field from the trenches results from structural differences between the magnetic material on the seed layer pillars and in the trenches, such as smaller grain size of the magnetic material on the seed layer pillars and a wider distribution of crystallographic axes of the magnetic material in the trenches. The seed layer may be made of a material substantially non-reactive with oxygen.