Polishing Composition for Nickel-Phosphorous Memory Disks
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Solution Overview
Problem
Conventional chemical-mechanical polishing methods and compositions are inadequate for achieving optimal planarity and surface finish of memory or rigid disks, leading to increased scratching and micro defects due to frictional forces and agglomeration of abrasive particles, which hinders the advancement of storage capacity and recording density.
Innovation Solution
A chemical-mechanical polishing composition comprising wet-process silica, an oxidizing agent that oxidizes nickel-phosphorous, a chelating agent, polyvinyl alcohol, and water, with a pH of 1 to 4, which reduces scratching and micro defects by maintaining colloidal stability and preventing agglomeration, thereby improving surface topography and removal rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If friction-reducing additives are added to the polishing composition, then frictional forces are reduced, but abrasive particles aggregate and scratching increases
Solution Approach 1:
The patent changes the chemical parameters of the polishing composition by specifying a pH range of 1-4 and using particular oxidizing agents (potassium permanganate, sodium persulfate, hydrogen peroxide) and chelating agents (EDTA, DTPA, HEDTA). These parameter changes control the chemical environment to prevent abrasive particle aggregation while maintaining low friction, resolving the contradiction between reducing friction and preventing scratching.
Solution Approach 2:
The patent introduces specific chemical intermediaries - oxidizing agents and chelating agents - that mediate between the abrasive particles and the nickel-phosphorous coating. These intermediaries control the chemical interactions to prevent aggregation while maintaining effective polishing, acting as mediators that resolve the conflict between friction reduction and scratching prevention.
2Ease of manufacture
If conventional CMP compositions are used, then the polishing process is simple, but surface finish and planarity are inadequate
Solution Approach 1:
The patent creates a composite polishing composition combining multiple components: wet-process silica (abrasive particles), oxidizing agents (potassium permanganate, sodium persulfate, hydrogen peroxide), chelating agents (EDTA, DTPA, HEDTA), and polyvinyl alcohol. This composite formulation achieves superior surface finish and planarity while maintaining process simplicity through a unified chemical-mechanical system.
Solution Approach 2:
The patent employs strong oxidizing agents (potassium permanganate, sodium persulfate, hydrogen peroxide) that accelerate the oxidation of nickel-phosphorous coating. This accelerated oxidation enables more effective material removal and improved surface finish while maintaining a simple polishing process, resolving the contradiction between process simplicity and manufacturing precision.
3Productivity
If abrasive particles are used to remove nickel-phosphorous, then removal rate increases, but scratching and micro defects increase
Solution Approach 1:
The patent optimizes the particle size parameters of wet-process silica (0.01-10 micrometers) and controls the chemical parameters (pH 1-4, oxidizing agent concentration, chelating agent concentration) to achieve effective material removal while minimizing scratching. These parameter optimizations allow high removal rates without proportionally increasing harmful effects.
Solution Approach 2:
The patent substitutes pure mechanical abrasion with a chemical-mechanical process where oxidizing agents and chelating agents chemically interact with the nickel-phosphorous coating to facilitate removal. This substitution reduces reliance on mechanical scratching and enables higher removal rates with fewer defects.
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 significantly reduces scratch counts and micro particle counts on nickel-phosphorous coated substrates, enhancing the surface finish and planarity, thus supporting higher storage capacities and improved recording densities.
Implementation Method 1
an oxidizing agent that oxidizes nickel-phosphorous
Implementation Method 2
a chelating agent
Implementation Method 3
wet-process silica
Data Source
AI summary
The invention provides a chemical-mechanical polishing composition containing wet-process silica, an oxidizing agent that oxidizes nickel-phosphorous, a chelating agent, polyvinyl alcohol, and water. The invention also provides a method of chemically-mechanically polishing a substrate, especially a nickel-phosphorous substrate, by 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.