Non-Uniform Write Gap Perpendicular Writer for Shingled Magnetic Recording
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Solution Overview
Problem
Shingled writing in perpendicular magnetic recording faces challenges with lower field gradient at track edges, leading to skewed transitions and limited track width due to one-side squeeze and write pole width constraints.
Innovation Solution
A write pole design with a symmetrical leading edge and a non-uniform write gap, featuring a recessed trailing edge with concave or convex curvature, enhances the field gradient at track edges by allowing a flexible track width independent of write pole width, achieved through specific fabrication methods involving plating, planarization, and selective etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional uniform write gap is used in shingled writing, then the write pole width can be tightly controlled, but the field gradient at track edge becomes lower leading to skewed transitions
Solution Approach 1:
The write gap thickness is made non-uniform along the trailing edge, with thinner regions at the corners and thicker region in the middle. This local variation in gap thickness creates corresponding local variations in field gradient, enhancing the field gradient specifically at the track edges where it is needed most for reducing transition skew, while maintaining adequate field strength at the track center.
Solution Approach 2:
The invention transitions from a uniform two-dimensional write gap to a three-dimensional non-uniform write gap structure. By varying the gap thickness in the vertical dimension along the trailing edge, the patent creates differentiated field gradients across the track width without requiring changes to the write pole planar dimensions, thus achieving improved track edge writing while maintaining manufacturing feasibility.
2Length of moving object
If the write pole width is reduced to achieve narrower track widths, then track width can be scaled down, but the field gradient at track edge deteriorates
Solution Approach 1:
The non-uniform write gap creates localized regions of enhanced field gradient at the track edges through thinner gap sections, allowing narrow track widths to be achieved without sacrificing edge field strength. The differentiated gap structure compensates for the reduced overall pole width by concentrating field strength where needed at the edges.
Solution Approach 2:
The invention changes the physical parameter of write gap thickness from uniform to non-uniform along the trailing edge. This parameter variation allows the field gradient distribution to be optimized independently of the write pole width, enabling narrow track widths while maintaining adequate field gradient at track edges through the thinner gap regions.
3Force
If a non-uniform write gap with recessed trailing edge is implemented, then field gradient at track edge is enhanced, but the device complexity increases
Solution Approach 1:
The non-uniform write gap structure is pre-formed during the write pole fabrication process using standard semiconductor manufacturing techniques such as selective etching or deposition. By incorporating the gap variation into the initial pole structure rather than adding it as a separate component, the complexity is minimized while achieving the desired field gradient enhancement.
Data Source
AI summary
A method of forming a PMR writer is disclosed wherein at least one of a recessed center section in the write pole trailing edge and a center recessed trailing shield is used to improve the field gradient at track edge. In all embodiments, there is a non-uniform write gap formed between the trailing edge and the trailing shield. The recessed portion of the write pole trailing edge and/or center recess of the trailing shield has a thickness from 10 to 40 nm in a down-track direction and a width in a cross-track direction of 20 to 200 nm. The distance between the center recess and a corner of the trailing edge is from 20 to 80 nm. A sequence of steps is provided to fabricate the two embodiments of the present invention.