Alumina Abrasive Coating for CMP Colloidal Stability
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Solution Overview
Problem
Existing chemical-mechanical polishing compositions for aluminum-containing substrates face issues with colloidal stability due to displacement of sulfonate-containing polymers or copolymers from alumina abrasive particles, leading to interparticle agglomeration and surface defects such as scratching.
Innovation Solution
A polishing composition comprising α-alumina particles coated with a copolymer of sulfonate and carboxylate monomers, an organic carboxylic acid as a complexing agent, and an alkyldiphenyloxide disulfonate surfactant, maintained at a pH of 1 to 6, which ensures colloidal stability and prevents agglomeration, thereby improving the polishing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If sulfonate-containing polymers or copolymers are used to coat alumina abrasives, then colloidal stability is improved, but other polishing components displace these polymers leading to agglomeration and surface defects
Solution Approach 1:
The patent uses a copolymer comprising both sulfonate-containing monomer units and carboxylate-containing monomer units coated on alumina abrasives. This composite polymer structure provides synergistic effects where the sulfonate groups anchor to the alumina surface while the carboxylate groups provide steric stabilization and resistance to displacement by other polishing components, thereby maintaining colloidal stability and preventing surface defects
Solution Approach 2:
The patent specifies controlling the pH of the polishing composition between 2 and 6, and the potential difference between alumina particles between -30mV and -70mV. These parameter controls ensure optimal electrostatic and steric stabilization of the copolymer-coated abrasives, preventing agglomeration while maintaining effective polishing action
2Productivity
If polishing components such as complexing agents and surface treatment polymers are added, then polishing performance is improved, but sulfonate-containing polymers are displaced from abrasive particles
Solution Approach 1:
The copolymer structure with both sulfonate and carboxylate functional groups provides dual functionality: the sulfonate groups maintain strong attachment to the alumina abrasive surface while the carboxylate groups provide enhanced steric stabilization that resists displacement by complexing agents and other polishing additives, thus maintaining both polishing efficiency and colloidal stability
Solution Approach 2:
Different portions of the copolymer chain serve different functions: the sulfonate-containing segments are positioned to interact with and anchor to the alumina surface, while the carboxylate-containing segments extend outward to provide steric stabilization and interact with the aqueous environment and other polishing components, creating a gradient of functional properties
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 solution provides improved colloidal stability and reduced surface defects, enhancing the polishing efficiency and defectivity of aluminum-containing substrates by maintaining the suspension of abrasive particles over time and preventing scratching.
Implementation Method 1
the abrasive is colloidally stable in the polishing composition
Implementation Method 2
The combination of the sulfonate monomer and carboxylate monomer provides both electrostatic and steric stabilization of the alumina abrasive particles
Implementation Method 3
abrading at least a portion of the surface of the substrate to remove at least some aluminum from the surface of the substrate
Implementation Method 4
a complexing agent for aluminum comprising an organic carboxylic acid
Implementation Method 5
wherein the polishing composition further comprises a surfactant; wherein the surfactant is an alkyldiphenyloxide disulfonate surfactant
Implementation Method 6
contacting a surface of the substrate with the polishing pad and the polishing composition, and abrading at least a portion of the surface
Data Source
AI summary
The invention provides a chemical-mechanical polishing composition comprising coated ?-alumina particles, an organic carboxylic acid, and water. The invention also provides a chemical-mechanical polishing composition comprising an abrasive having a negative zeta potential in the polishing composition, an organic carboxylic acid, at least one alkyldiphenyloxide disulfonate surfactant, and water, wherein the polishing composition does not further comprise a heterocyclic compound. The abrasive is colloidally stable in the polishing composition. The invention further provides methods of polishing a substrate with the aforesaid polishing compositions.