Nickel-Phosphorus Disk Polishing Composition
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional chemical-mechanical polishing methods struggle to effectively minimize microwaviness and edge roll-off in memory or rigid disks while maintaining a high removal rate, which is crucial for improving storage capacity and reducing damage from magnetic head interactions.
Innovation Solution
A chemical-mechanical polishing composition comprising fumed alumina particles, alpha alumina particles, substantially spherical silica particles, hydrogen peroxide, an iminocarboxylic acid, and water, or an oxidizing agent like OXONE® and sodium persulfate, along with a complexing agent, is used to polish substrates, reducing microwaviness and edge roll-off without sacrificing removal rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the polishing rate is increased to improve productivity, then the removal rate of the disk increases, but the microwaviness of the disk surface increases
Solution Approach 1:
The polishing composition is segmented into multiple abrasive particle types with different size distributions (first population: 0.01-1.0 microns, second population: 1.0-10.0 microns). This segmentation allows different particle sizes to work synergistically - finer particles fill valleys and reduce micrawaviness while coarser particles provide overall material removal, thus achieving both high removal rate and low micrawaviness simultaneously
Solution Approach 2:
The invention uses a composite abrasive system combining multiple particle types (alumina, silica, zirconia, titania) with different physical and chemical properties. This composite approach creates a polishing slurry where particles complement each other's functions - some particles provide mechanical abrasion for high removal rate while others provide chemical etching for surface smoothing, resolving the contradiction between productivity and precision
2Productivity
If the polishing pressure on the disk edges is increased to improve removal rate, then the edges receive higher abrasion, but edge roll-off increases forming curved contours
Solution Approach 1:
The polishing composition is designed with local quality considerations by incorporating particles with specific size ranges and properties that distribute polishing action more uniformly across the disk surface. The multi-modal particle size distribution ensures that particles of appropriate sizes reach different regions (center and edges) with effective polishing action, reducing the pressure concentration at edges that causes roll-off while maintaining overall removal rate
3Quantity of substance
If the flying height of the magnetic head is reduced to increase storage capacity, then recording density improves, but the disk surface micrawaviness causes airbearing resonance and head-to-disk spacing modulation
Solution Approach 1:
The polishing composition performs preliminary action by removing surface irregularities and micrawaviness before the disk enters service. The chemical-mechanical polishing process pre-conditiones the surface to be extremely flat and uniform, eliminating the micrawaviness that would otherwise cause airbearing resonance and spacing modulation at low flying heights, thus enabling high storage capacity operation
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 proposed solution effectively reduces microwaviness and edge roll-off, enhancing the planarity of memory or rigid disks and maintaining or increasing the removal rate, thus improving overall polishing performance and storage capacity.
Implementation Method 1
polishing is performed using a combination of an abrasive, a polishing pad, and a liquid carrier, in which the abrasive may be suspended in the liquid carrier
Implementation Method 2
the rate of abrasion is at least in part a function of pressure applied, the edges of the disk experience a higher rate of abrasion than the rest of the disk
Implementation Method 3
hydrogen peroxide
Implementation Method 4
an iminocarboxylic acid
Data Source
AI summary
The invention provides a chemical-mechanical polishing composition comprising alpha alumina, fumed alumina, silica, an oxidizing agent that oxidizes nickel-phosphorous, a complexing agent, and water. The invention also provides a method of chemically-mechanically polishing a substrate comprising contacting a substrate with a polishing pad and the chemical-mechanical polishing composition, moving the polishing pad and the polishing composition relative to the substrate, and abrading at least a portion of the substrate to polish the substrate.