Hard Disk Drive Write Pole Patterning With Tri-Tone Phase Masks
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Solution Overview
Problem
Existing lithographic methods for manufacturing write poles in hard disk drives struggle to achieve precise and efficient patterning, particularly in forming narrow track widths and maintaining high data density, due to limitations in photolithographic processes.
Innovation Solution
Employing a tri-tone attenuated phase shift mask comprising a patterned opaque material layer, partially-transparent strips, and assist bars to guide the lithographic exposure process, allowing for precise patterning of the write pole with a uniform width region and flare region, which enhances the manufacturing process by using a tri-tone lithographic mask with partially-transparent assist bars to achieve narrower and more precise features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithographic masks are used for patterning write poles, then the manufacturing process is simpler, but the manufacturing precision and data density are insufficient
Solution Approach 1:
The lithographic mask is segmented into multiple layers: a first mask layer with main pattern features and a second mask layer with assist features. This segmentation allows each layer to serve specific functions - the first layer defines the primary write pole geometry while the second layer provides exposure assistance, thereby improving patterning precision without requiring complete redesign of a single complex mask layer
Solution Approach 2:
The second mask layer acts as an intermediary element that mediates the exposure process by providing assist features that enhance the formation of write pole features. These assist features facilitate better light exposure distribution and improve the precision of the final pattern without being part of the final write pole structure itself
2Length of moving object
If conventional lithographic methods are used, then the process is faster and simpler, but the track width cannot be sufficiently narrowed for high data density
Solution Approach 1:
The mask structure implements local quality by providing different features in different regions: the first mask layer contains main pattern features for the write pole body, while the second mask layer contains assist features specifically positioned to enhance exposure in critical regions. This localized optimization enables narrower track widths in specific areas without compromising overall manufacturing efficiency
Solution Approach 2:
The assist features in the second mask layer perform preliminary action by pre-establishing exposure patterns that facilitate the formation of narrow write pole features. By preparing the exposure field in advance with these assist features, the process achieves narrower track widths without requiring multiple iterative exposure steps, thereby maintaining manufacturing efficiency
3Reliability
If a single-layer mask is used, then the mask fabrication is simpler, but the depth of focus and dose sensitivity are insufficient for precise patterning
Solution Approach 1:
The mask is segmented into multiple functional layers, where the first mask layer handles the primary pattern definition and the second mask layer handles exposure assistance. This segmentation improves depth of focus by distributing functional requirements across layers, allowing each layer to be optimized for its specific purpose without compromising the other
Solution Approach 2:
The multi-layer mask structure achieves multi-functionality by combining pattern definition and exposure assistance in a single integrated mask system. The first mask layer provides the primary pattern while the second mask layer provides exposure assistance, and both functions work together to improve depth of focus and dose sensitivity without requiring separate mask systems
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 tri-tone lithographic mask enables the formation of write poles with narrower straight portions, improving data density and manufacturing precision, offering a higher depth of focus and reduced dose sensitivity, thereby enhancing the performance of hard disk drives.
Implementation Method 1
tri-tone attenuated phase shift mask
Implementation Method 2
lithographically exposing the photoresist layer through the lithographic mask
Data Source
AI summary
A write pole of a write head of a hard disk drive can be manufactured by forming a photoresist layer over a magnetic material layer located over a substrate, disposing a tri-tone lithographic mask over the photoresist layer, lithographically exposing the photoresist layer through the lithographic mask, developing the photoresist layer to form a patterned photoresist layer, and patterning the magnetic material layer into the write pole by removing portions of the magnetic material layer that are not covered by the photoresist layer. The tri-tone lithographic mask includes a patterned opaque material layer and a patterned partially-transparent material layer located over a transparent substrate. The patterned opaque material layer includes a uniform width region and a flare region. The patterned partially-transparent material layer includes a pair of partially-transparent strips extending adjacent to a respective edge of the patterned opaque material layer, and partially-transparent assist bars.