Self-aligned Write Pole for PMR Side Shields
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Solution Overview
Problem
In perpendicular magnetic recording, achieving symmetric positioning of the write pole relative to side shields is challenging due to the lack of self-alignment methods, leading to issues like reduced yield, fringe effects, and uneven side erasure.
Innovation Solution
A self-aligning process is developed where a trench is etched into a dielectric layer, lined with ruthenium, and filled with soft magnetic material, allowing precise control of non-magnetic layers to determine the write pole's location without optical alignment, ensuring symmetric positioning between side shields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If subtractive methods (RIE, IBE) are used to etch opening in magnetic shield layer followed by standard ALD, electroplating, and CMP methods to form write pole, then write pole can be formed inside the opening, but the positioning of the write pole structure between side and trailing shields is not self-aligned, leading to reduced yield and fringe effects
Solution Approach 1:
The write pole structure is formed to be self-aligned relative to the side and trailing shields through the deposition sequence and thickness control, eliminating the need for optical alignment steps. The ruthenium layer thickness (50-200 nm) and soft magnetic layer thickness are precisely controlled to achieve automatic positioning of the write pole at the desired location between shields.
Solution Approach 2:
A ruthenium layer is deposited over the entire substrate before forming the write pole structure. This preliminary ruthenium layer serves as a reference plane and alignment reference, allowing subsequent etching and deposition steps to automatically position the write pole correctly relative to the shields without requiring additional alignment operations.
2Reliability
If write pole is not symmetrically located within the space between side shields, then manufacturing process is simpler, but problems arise including reduction in overall process yield, fringe effects at pole edge farthest from shield, and uneven side erasure
Solution Approach 1:
The structure is designed so that the write pole automatically positions itself symmetrically between the side shields through the controlled deposition of ruthenium and soft magnetic layers. The self-alignment mechanism ensures consistent positioning without requiring complex optical alignment equipment or procedures, thereby improving yield while maintaining manageable process complexity.
3Manufacturing precision
If optical alignment step is used to position write pole between side shields, then positioning accuracy can be achieved, but the process complexity increases and yield is reduced
Solution Approach 1:
The write pole structure achieves automatic self-alignment through the sequential deposition of ruthenium and soft magnetic layers with controlled thicknesses. This eliminates the need for optical alignment steps entirely, maintaining high positioning accuracy while improving manufacturing yield by removing a complex and yield-limiting process step.
Solution Approach 2:
The optical alignment step is completely removed from the manufacturing process. The alignment function is achieved through the physical structure and deposition sequence itself, extracting the unnecessary optical alignment operation that was reducing productivity and yield.
4Productivity
If side shields are added to reduce fringe effects and minimize side erasure, then track density can be maximized, but the complexity of achieving symmetric write pole positioning increases
Solution Approach 1:
The write pole structure is designed to self-align with the side shields through controlled layer deposition. The ruthenium layer thickness (50-200 nm) and soft magnetic layer thickness are precisely controlled to ensure the write pole automatically positions itself symmetrically between the side shields, achieving the required positioning precision to maximize track density without increasing manufacturing complexity.
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 eliminates optical alignment steps, ensuring consistent write pole placement, reducing yield loss and fringe effects, and enabling higher track density and extendibility to high TPI applications.
Implementation Method 1
a layer of ruthenium (or other suitable non-magnetic material) whose thickness is uniform and carefully controlled
Implementation Method 2
filled with soft magnetic material
Data Source
AI summary
A magnetic pole suitable for perpendicular magnetic recording is described. This write pole is symmetrically located relative to its side shields and has at least three additional surfaces that are disposed to lie in planes that are normal to the substrate's top surface.