Perpendicular Magnetic Recording Head Pole Width Control
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Solution Overview
Problem
Conventional perpendicular magnetic recording (PMR) write heads experience variations in pole width due to chemical mechanical polish (CMP) process inconsistencies, leading to inconsistent magnetic flux density and potential skewing of the pole tip, resulting in undesirable writing on adjacent tracks.
Innovation Solution
A PMR write head design featuring a pole tip with a rectangular upper portion and an inverted trapezoidal lower portion, where the upper portion is trimmed to a consistent width using ion milling processes, ensuring the lower portion retains its inverted trapezoidal shape, thereby maintaining consistent pole width and preventing skewing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a conventional inverted trapezoidal pole tip is used and CMP process is applied, then the pole tip surface is planarized, but the pole width varies significantly due to CMP process variations
Solution Approach 1:
The pole tip is divided into two distinct geometric segments: an upper rectangular portion and a lower inverted trapezoidal portion. This segmentation allows each portion to serve its specific function - the rectangular upper portion provides consistent pole width for precise track writing, while the lower trapezoidal portion maintains magnetic flux density. By separating these functions into distinct geometric segments, the design resolves the contradiction between surface planarity and pole width consistency.
Solution Approach 2:
Different portions of the pole tip are given different geometric properties tailored to their specific functions. The upper portion has a rectangular cross-section with vertical sides to ensure consistent pole width and prevent skewing during recording. The lower portion has an inverted trapezoidal cross-section to maintain magnetic flux density. This local differentiation of geometric quality allows the pole tip to simultaneously achieve surface planarity and pole width consistency.
2Manufacturing precision
If the pole tip is trimmed to reduce skewing, then writing accuracy on adjacent tracks is improved, but the magnetic flux density may be compromised
Solution Approach 1:
The pole tip is segmented into an upper rectangular portion that extends vertically with constant width, and a lower inverted trapezoidal portion that tapers toward the bottom. The rectangular upper portion ensures consistent pole width for precise track writing and prevents skewing during recording. The lower inverted trapezoidal portion maintains magnetic flux density by providing an gradual transition. This segmentation allows the design to simultaneously achieve writing accuracy and maintain magnetic flux density.
Solution Approach 2:
The upper portion of the pole tip is given rectangular geometry with vertical sides to provide consistent pole width and prevent skewing, ensuring writing accuracy on adjacent tracks. The lower portion is given inverted trapezoidal geometry to maintain magnetic flux density. This local differentiation allows the pole tip to optimize both writing precision and magnetic performance without compromise.
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
The design achieves consistent pole width and reduced skewing, enhancing recording accuracy and reliability by minimizing the impact of CMP process variations and preventing writing on adjacent tracks.
Implementation Method 1
The track width is typically determined by an ion milling process that removes excess material from the edges of the main pole layer
Implementation Method 2
a subsequent chemical mechanical polish (CMP) process that planarizes the main pole layer 3
Implementation Method 3
Magnetic flux generated in the main pole layer passes through the pole tip into a magnetic media and then back to the write head by entering the flux return pole
Data Source
AI summary
A main pole layer is deposited within an opening in a patterned photoresist layer on a substrate. The photoresist is thinned to expose an upper portion of a pole tip region that is then trimmed to a rectangular shape while a lower portion retains an inverted trapezoidal shape. Thereafter, a second trimming process forms a pole tip with a first width in the upper rectangular portion and a second thickness and second width which is less than the first width in the lower portion. A CMP step subsequently thins the upper portion to a first thickness of 0.04 to 0.08 microns while the second thickness remains at 0.16 to 0.32 microns. The bottom surface of the lower portion along the ABS becomes the trailing edge in a recording operation. The pole tip has a consistent first width (track width) that is not influenced by CMP process variations.