Patterned Perpendicular Magnetic Recording Media Fabrication
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Solution Overview
Problem
Conventional magnetic recording media face challenges in achieving high areal recording density due to the superparamagnetic effect, which causes instability in magnetization as grain size decreases, leading to losses and noise, and existing fabrication methods for patterned media are inefficient and prone to topographical issues.
Innovation Solution
A method for fabricating patterned perpendicular magnetic recording media using a layer stack with a magnetically soft underlayer and non-magnetic interlayer, involving a masking layer, resist layer, and thermal imprint lithography to form recesses, which are then filled with a magnetically hard material, reducing the number of patterning steps and maintaining compatibility with automated manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional continuous magnetic film is used to increase areal recording density, then storage capacity increases, but thermal stability is lost due to the superparamagnetic effect
Solution Approach 1:
The continuous magnetic film is divided into discrete magnetic islands or bits separated by non-magnetic gaps. Each island contains a single magnetic domain with stable magnetization direction, preventing the superparamagnetic effect while maintaining high areal density through precise spatial segmentation of magnetic recording elements
Solution Approach 2:
The magnetic properties are made non-uniform across the medium: magnetic islands have high coercivity and stable magnetization, while the gap regions are non-magnetic or have different magnetic properties. This local differentiation allows stable data storage in magnetic regions while preventing unwanted magnetic interactions in gap regions
2Quantity of substance
If grain size is reduced to increase bit density, then areal recording density increases, but magnetization becomes unstable due to superparamagnetic effect
Solution Approach 1:
Rather than relying on large grain sizes for thermal stability, the invention segments the magnetic layer into discrete islands where each island is small enough for high density but large enough to maintain stable single-domain magnetization. The segmentation into isolated bits prevents thermal fluctuation effects that plague continuous fine-grained media
Solution Approach 2:
The invention transitions from a continuous two-dimensional magnetic plane to a patterned structure with vertical separation between magnetic islands and non-magnetic gaps. This dimensional restructuring allows small feature sizes while maintaining magnetic stability through spatial isolation
3Manufacturing precision
If existing fabrication methods are used for patterned media, then pattern formation is achieved, but manufacturing complexity and topographical issues increase
Solution Approach 1:
A masking layer is deposited over the magnetic layer before patterning. This preliminary masking structure protects the magnetic layer during etching and simplifies the patterning process by providing a sacrificial layer that defines the magnetic island patterns without requiring complex direct patterning of the magnetic material itself
Solution Approach 2:
The masking layer serves as an intermediary between the patterning process and the magnetic layer. It transfers the pattern definition to the magnetic layer through controlled etching, avoiding the need for complex direct patterning methods and reducing topographical damage to the magnetic recording elements
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 effectively increases areal recording density while minimizing noise and errors, enhancing magnetic performance and reducing the complexity of the writing process, with improved bit patterned media that can be cost-effectively manufactured on a large scale.
Implementation Method 1
thermal imprint lithography to form recesses
Implementation Method 2
The magnetically soft underlayer serves to guide magnetic flux emanating from the head through the magnetically hard perpendicular recording layer
Data Source
AI summary
A method of fabricating a patterned perpendicular magnetic recording medium comprises steps of: (a) providing a layer stack including a magnetically soft underlayer (“SUL”) and an overlying non-magnetic interlayer; (b) forming a masking layer on the non-magnetic interlayer; (c) forming a resist layer on the masking layer; (d) forming a pattern of recesses extending through the resist layer and exposing spaced apart surface portions of the masking layer; (e) extending the pattern of recesses through the masking layer to expose spaced apart surface portions of the interlayer; and (f) at least partially filling the pattern of recesses with a magnetically hard material to form a perpendicular magnetic recording layer.