Tunable Seed Layer for Perpendicular Magnetic Recording Write Heads
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Solution Overview
Problem
Conventional perpendicular magnetic recording (PMR) write head manufacturing techniques face challenges in achieving a uniform bottom gap to side gap (BG/SG) ratio, leading to poor step coverage and decreased writeability due to re-deposition and sputtering during pre-cleaning etching, resulting in a BG/SG ratio of less than 88%, which worsens with miniaturization.
Innovation Solution
A process involving ion beam deposition (IBD) and physical vapor deposition (PVD) to create a tunable non-magnetic gap layer with a BG/SG ratio between 90% and 120% by modifying the IBD deposition angle and using bilayer seed layers, ensuring conformal coating and maintaining or increasing the bottom gap thickness relative to the side gap, thereby reducing flux leakage and enhancing writeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CVD Ru process is used for depositing the seed layer, then a highly conductive and continuous Ru film can be deposited, but the step coverage is poor resulting in a bottom gap to side gap ratio of less than 88%
Solution Approach 1:
The patent segments the seed layer deposition into multiple distinct layers with different functions: a PVD seed layer for achieving uniform thickness and good step coverage, followed by an ALD Ru layer for providing conductivity and continuity. This segmentation allows each layer to optimize its specific function without compromise.
Solution Approach 2:
The patent uses a composite structure combining different deposition methods and materials: PVD-deposited seed layer (typically Ta or W) combined with ALD-deposited Ru layer. This composite approach leverages the advantages of each material and deposition method to achieve both good step coverage and electrical conductivity.
2Productivity
If miniaturization is pursued to reduce feature size, then device density increases, but the bottom gap thickness decreases leading to degraded writeability
Solution Approach 1:
The patent applies preliminary action by using PVD deposition to create a uniformly thick seed layer before the main Ru deposition. This pre-established uniform layer provides a foundation that maintains consistent bottom gap thickness even as device dimensions are reduced for miniaturization.
Solution Approach 2:
The patent changes the deposition parameters by switching from CVD to PVD method, which fundamentally alters the deposition mechanics. PVD's line-of-sight deposition geometry and lower re-deposition rates enable maintenance of bottom gap thickness at smaller feature sizes, allowing continued miniaturization without writeability degradation.
3Reliability
If pre-cleaning etching is performed to clean the trench, then surface cleanliness improves, but re-deposition and sputtering reduce the bottom gap thickness
Solution Approach 1:
The patent performs preliminary cleaning of the trench surface before seed layer deposition to remove contaminants. This preliminary action ensures good adhesion and interface quality without requiring aggressive etching that would cause re-deposition or sputtering damage to the bottom gap region.
Solution Approach 2:
The PVD-deposited seed layer acts as an intermediary protective layer during subsequent processing steps. This intermediate layer protects the bottom gap region from re-deposition and sputtering damage while still allowing the trench to be adequately cleaned, thus mediating between the need for cleanliness and the need to preserve bottom gap thickness.
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 process allows for a tunable BG/SG ratio of 90-120%, improving writeability by maintaining or increasing the bottom gap thickness, reducing flux leakage, and enabling better performance in miniaturized PMR writer main poles.
Implementation Method 1
Ion beam deposition (IBD) is a physical vapor deposition (PVD) process used to deposit thin films
Implementation Method 2
physical vapor deposition (PVD) process used to deposit a non-magnetic gap layer
Data Source
AI summary
A writer main pole for a perpendicular magnetic recording system is provided. The writer pole has a tunable bottom gap to side gap ratio, and may be formed using deposition of a first seed layer through an ion beam deposition process, deposition of a second seed layer through a physical vapor deposition process, and deposition of a non-magnetic gap layer through a chemical vapor deposition process.