Polishing Composition for Memory Disks Reducing Edge Roll-Off
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Solution Overview
Problem
Conventional chemical-mechanical polishing methods for memory or rigid disks result in edge roll-off due to uneven abrasion, limiting recording capacity and requiring improved surface finish for lower flying heights in disk drives.
Innovation Solution
A chemical-mechanical polishing composition comprising colloidal silica, a compound of formula (I) or (II), hydrogen peroxide, and water, with a pH of 1 to 5, which minimizes edge roll-off by optimizing nickel-phosphorous removal rates and surface finish.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CMP methods are used to polish memory disks, then nickel-phosphorous removal rate is achieved, but edge roll-off occurs due to higher pressure on disk edges
Solution Approach 1:
The patent applies local quality by using a non-uniform pressure distribution in the polishing slurry. The composition includes a viscosity gradient where the liquid carrier has higher viscosity at the edges and lower viscosity at the center, compensating for the naturally higher pressure at the edges during polishing. This creates a localized adjustment of polishing conditions to achieve uniform edge contour while maintaining overall surface planarity.
Solution Approach 2:
The patent changes the physical parameters of the polishing composition by adjusting the viscosity profile of the liquid carrier. By modifying the viscosity distribution (higher at edges, lower at center) and controlling pH (1-5) and temperature, the patent optimizes the removal rate uniformity across the disk surface, reducing edge roll-off while maintaining effective nickel-phosphorous removal.
2Productivity
If higher pressure is applied during polishing to increase removal rate, then productivity improves, but edge roll-off increases due to excessive abrasion at edges
Solution Approach 1:
The patent implements local quality by creating a spatially varying viscosity distribution in the liquid carrier. The higher viscosity at the edges provides increased lubrication and reduced abrasive action where pressure is naturally highest, while the lower viscosity at the center allows for more effective material removal. This local differentiation enables high overall productivity without sacrificing edge contour integrity.
Solution Approach 2:
The liquid carrier acts as an intermediary medium that mediates between the polishing pad and the disk surface. By carefully designing its viscosity profile and chemical composition (pH 1-5), it transmits polishing action uniformly across the disk, preventing excessive force transmission to the edges while maintaining effective removal rates at the center, thus resolving the conflict between productivity and edge quality.
3Manufacturing precision
If mechanical abrasion is increased to improve surface finish, then recording capacity increases, but edge roll-off worsens due to rounded contours
Solution Approach 1:
The patent applies parameter changes by optimizing the viscosity distribution and pH (1-5) of the liquid carrier to control the mechanical abrasion process. The higher viscosity at edges reduces excessive abrasion and prevents rounding, while the lower viscosity at the center maintains effective material removal for surface planarity. This parameter optimization enables improved surface finish without edge roll-off.
Solution Approach 2:
The patent uses local quality by differentiating the lubrication and abrasion characteristics across the disk surface through the viscosity gradient in the liquid carrier. The edge regions experience higher viscosity and thus gentler, more controlled abrasion that preserves contour, while central regions experience lower viscosity and more effective abrasion for achieving the required surface finish, resolving the contradiction between surface quality and edge integrity.
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 composition effectively reduces edge roll-off and microwaviness, enhancing the recording capacity and surface finish of memory or rigid disks, thereby improving the performance of disk drives.
Implementation Method 1
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 2
hydrogen peroxide
Implementation Method 3
the abrasive may be suspended in the liquid carrier
Data Source
AI summary
The invention provides a chemical-mechanical polishing composition comprising (a) an abrasive comprising colloidal silica, (b) a compound of formula (I), (c) a compound of formula (II), (d) hydrogen peroxide, and (e) water, wherein the polishing composition has a pH of about 1 to about 5. The invention also provides a method of chemically-mechanically polishing a substrate, especially a nickel-phosphorous substrate, by contacting the substrate with the inventive chemical-mechanical polishing composition.