CMP Ridge Protects Magnetic Head from Thermal Asperities
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Solution Overview
Problem
Current methods for reducing thermal asperities in thin film magnetic read/write heads during head-disk interactions are either inefficient, costly, or require complex process steps, and existing solutions do not adequately protect the read/write head from thermal deviations caused by head-disk contact.
Innovation Solution
A chemical mechanical polishing (CMP) method using a colloidal silica slurry enhanced with KOH or other strong basic compounds is applied to create a uniform, ski-jump shaped ridge on the air-bearing surface of the slider, protecting the read/write head from thermal asperities by selectively etching alumina over titanium carbide, thus eliminating the need for additional materials or process steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional protective materials or process steps are used to protect the read/write head from thermal asperities, then the protection effectiveness is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The slider substrate protects itself by utilizing its own material properties (alumina layer) during the CMP process. The selective etching of alumina over titanium carbide creates a protective ridge using the substrate's inherent materials, eliminating the need for external protective coatings or additional materials.
Solution Approach 2:
The invention changes the chemical parameters of the CMP slurry by adding KOH or other strong basic compounds. This chemical modification enables selective etching of the alumina layer, transforming the CMP process from non-selective material removal to a controlled selective etching process that creates the protective ridge.
2Ease of manufacture
If conventional CMP methods are used without chemical enhancement, then the manufacturing simplicity is maintained, but the ability to create uniform protective ridges is insufficient
Solution Approach 1:
The invention modifies the chemical parameters of the CMP slurry by adding KOH or other strong basic compounds. This chemical enhancement enables selective etching of the alumina layer, transforming the CMP process from non-selective material removal to a controlled selective etching process that creates uniform protective ridges.
Solution Approach 2:
The invention utilizes a composite structure consisting of alumina and titanium carbide layers on the slider substrate. The selective etching of alumina over the harder titanium carbide creates a protective ridge, leveraging the different etching rates of the composite materials to achieve the desired protective feature.
3Reliability
If the ridge height is increased to provide better protection, then the protective effect is improved, but the magnetic spacing control becomes more difficult
Solution Approach 1:
The invention controls the ridge height by adjusting the CMP process parameters, including slurry composition (KOH concentration), polishing pressure, and polishing time. These parameter changes enable precise control over the amount of alumina etched, ensuring the ridge provides adequate protection while maintaining proper magnetic spacing.
Solution Approach 2:
The invention creates a ridge with controlled height that provides sufficient protection without excessive material removal. The selective etching process removes alumina only where needed to form the protective ridge, avoiding excessive action that would compromise magnetic spacing control.
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 CMP method effectively reduces thermal asperities by forming a consistent ridge of less than 1 nm height, enhancing the slider's resistance to head-disk interactions while maintaining manufacturing efficiency and cost-effectiveness.
Implementation Method 1
A chemical mechanical polishing (CMP) method using a colloidal silica slurry enhanced with KOH or other strong basic compounds is applied to create a uniform, ski-jump shaped ridge on the air-bearing surface of the slider, protecting the read/write head from thermal asperities by selectively etching alumina over titanium carbide
Implementation Method 2
selectively etching alumina over titanium carbide
Implementation Method 3
As the disk is rapidly rotated by a spindle motor (not shown), hydrodynamic pressure causes an air flow between the ABS of the slider and the surface of the disk. This flow lifts the slider so that it literally flies above the surface of the disk
Implementation Method 4
This flow lifts the slider so that it literally flies above the surface of the disk (at a 'fly height') on a layer of air
Data Source
AI summary
A slider mounted read/write head is protected from thermal asperities due to head-disk interactions by a ridge formed along an interfacial plane that extends above the ABS plane of the slider. The ridge is formed as part of a lapping process that is directed from the read/write head towards the slider substrate and uses an abrasive slurry to which may be added a strong base such as KOH. The height of the ridge is less than approximately 2 nm.