Patterned Magnetic Recording Disk Capping Layer for Diffusion Control
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Solution Overview
Problem
Patterned perpendicular magnetic recording media face issues with magnetic material in trenches causing noise in readback signals and affecting writing, due to uncontrolled chemical reactions between diffusion material and the recording layer material on pillars.
Innovation Solution
A nonmagnetic capping layer is deposited in the trenches to prevent diffusion of substrate material into the recording layer on pillars, allowing for controlled annealing to render trenches nonmagnetic without affecting the pillars, using materials like silicon or germanium as diffusion materials and silicon oxide or nitride for pillars, and refractory metals for the capping layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If annealing is performed to render trenches nonmagnetic through diffusion material reacting with recording layer material, then magnetic noise from trenches is reduced, but diffusion material may also react with recording layer material on pillars causing adverse effects
Solution Approach 1:
The patent segments the diffusion process by spatially separating where diffusion occurs (in trenches) from where it should not occur (on pillars). The pre-formed pillars act as physical boundaries that prevent diffusion material from reaching the recording layer on pillars, while allowing diffusion to proceed in the trench regions to eliminate magnetic noise.
Solution Approach 2:
The pillars are pre-formed before the annealing process that causes diffusion. This preliminary action creates protective structures in advance that prevent diffusion material from reaching the recording layer on pillars during subsequent thermal processing, while still allowing diffusion to occur in trench regions.
2Manufacturing precision
If higher temperature and longer annealing times are used to ensure complete diffusion reaction, then trenches are more effectively rendered nonmagnetic, but the risk of adverse reactions with recording layer on pillars increases
Solution Approach 1:
The pre-formed pillars serve as a protective cushion or barrier before the annealing process begins. They physically block diffusion material from reaching the recording layer on pillars, providing a safety margin that allows more aggressive annealing conditions (higher temperature, longer time) to be used in trench regions without risking damage to the recording layer on pillars.
3Ease of manufacture
If pre-etched substrates with trenches are used to enable low-cost manufacturing, then production cost is reduced, but magnetic material in trenches creates noise and affects writing
Solution Approach 1:
The patent converts the harmful magnetic material in trenches into a beneficial nonmagnetic state through controlled diffusion reactions. By annealing the pre-formed structure, the magnetic recording layer material in trenches reacts with diffusion material to become nonmagnetic, transforming the original harm (magnetic noise) into a benefit (eliminated interference) while preserving the low-cost manufacturing advantage of pre-etched substrates.
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 solution effectively eliminates magnetic noise from trenches, ensuring robust manufacturing with higher temperature and longer annealing times, while maintaining the magnetic properties of the recording layer on pillars, thus enhancing signal-to-noise ratio and recording performance.
Implementation Method 1
The substrate has material in the trenches that diffuses into the magnetic recording layer material in the trenches during an annealing process
Implementation Method 2
The diffusion material chemically reacts or interdiffuses with one or more of the elements in the recording layer material to render the trenches nonmagnetic
Implementation Method 3
The presence of the capping layer during the annealing process suppresses the diffusion of material from the substrate to the surface in the trenches
Implementation Method 4
The substrate is then heated to an elevated temperature and for a time sufficient to cause the recording layer material in the trenches and the material in the substrate to diffuse into one another and chemically react
Data Source
AI summary
A magnetic recording disk drive has a patterned perpendicular magnetic recording disk of the type that has spaced-apart pillars with magnetic material on their ends and with trenches between the pillars that are nonmagnetic regions. A nonmagnetic capping layer is located in the trenches above the nonmagnetic regions. The substrate has diffusion material in the trenches that when heated will diffuse into the magnetic recording layer material and chemically react with it. The pillars are formed of material that will not diffuse into the recording layer. The recording layer is formed over the entire substrate and a nonmagnetic capping layer that is not chemically reactive with the diffusion material is formed over the recording layer in the trenches. The substrate is annealed to cause the recording layer material in the trenches and the material in the substrate to diffuse into one another and chemically react to render the trenches nonmagnetic. The capping layer suppresses the diffusion of material from the substrate to the surface in the trenches and thus prevents migration of diffusion material to the recording layer material on the ends of the pillars.