Silicon Wafer Polishing Liquid Composition for Defect Reduction
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Solution Overview
Problem
Conventional polishing liquid compositions for silicon wafers face issues with storage stability and insufficient removal of silica particle agglomerates and water-insoluble matters, leading to increased surface defects and reduced productivity due to high viscosity and clogged filters.
Innovation Solution
A polishing liquid composition containing silica particles, a nitrogen-containing basic compound, and a water-soluble macromolecular compound with a specific weight average molecular weight and constitutional unit, which improves storage stability, reduces surface roughness and defects, and maintains a favorable polishing rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polishing liquid compositions are used, then polishing function is provided, but storage stability deteriorates due to agglomeration of silica particles and presence of water-insoluble matters
Solution Approach 1:
A water-soluble polymer compound is introduced as an intermediary substance to mediate between silica particles and the aqueous medium. This polymer prevents agglomeration of silica particles by providing steric stabilization, ensuring uniform dispersion and maintaining storage stability without requiring complex filtration systems.
Solution Approach 2:
The invention changes the chemical parameters of the polishing liquid by controlling pH (8.0-12.0) and selecting specific polymer compounds with appropriate molecular weights and concentrations. These parameter changes optimize the electrostatic and steric repulsion between silica particles, preventing agglomeration and improving storage stability.
2Manufacturing precision
If high viscosity polishing liquid is used to improve defect reduction, then surface roughness decreases, but productivity reduces due to filter clogging
Solution Approach 1:
The invention extracts and removes water-insoluble matters from the polishing liquid composition through careful selection of water-soluble polymer compounds and controlled synthesis conditions. This extraction eliminates the root cause of filter clogging, allowing high viscosity liquids to be used without compromising productivity.
Solution Approach 2:
The polishing liquid is prepared in advance with optimized composition and uniform silica particle dispersion, preventing agglomeration before the polishing process. This preliminary action ensures that the liquid maintains its flow properties during storage and use, avoiding filter clogging while providing defect reduction benefits.
3Productivity
If silica particle agglomerates are present to maintain polishing rate, then polishing speed is maintained, but surface defects increase
Solution Approach 1:
The invention creates a dynamic equilibrium where silica particles remain dispersed during storage but can effectively interact with the wafer surface during polishing. The water-soluble polymer compound provides conditional stabilization, allowing particle dispersion in storage while enabling controlled particle-wafer interaction during the polishing process.
Solution Approach 2:
The polishing liquid exhibits different local properties: uniform particle dispersion in the bulk liquid during storage, and controlled particle deposition on the wafer surface during polishing. The polymer compound enables this local quality differentiation, preventing agglomeration in storage while allowing effective polishing action on the surface.
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 enhances storage stability, reduces surface roughness and defects, and ensures a high polishing rate, addressing the limitations of previous compositions by preventing agglomeration and improving interaction between silica particles and the wafer surface.
Implementation Method 1
a water-soluble macromolecular compound including 10 wt% or more of a constitutional unit I... improves storage stability, reduces surface roughness and defects
Implementation Method 2
a polishing liquid composition for chemical-mechanical polishing by use of colloidal silica and an alkali compound
Implementation Method 3
at least one nitrogen-containing basic compound selected from the group consisting of an amine compound and an ammonium compound
Data Source
AI summary
A polishing liquid composition for a silicon wafer, wherein the composition comprises silica particles (component A), at least one kind of nitrogen-containing basic compound (component B) selected from an amine compound and an ammonium compound, and a water-soluble macromolecular compound (component C) that contains 10 wt% or more of a constitutional unit I represented by a general formula (1) below and has a weight average molecular weight of 50,000 or more and 1,500,000 or less; and the pH at 25°C is 8.0 to 12.0. In the general formula (1), R1 and R2 each independently represents a hydrogen, a C1 to C8 alkyl group, or a C1 to C2 hydroxyalkyl group, and R1 and R2 are never both hydrogens.