High-Concentration Silica Sol Production via Thermal-Stable Dispersing Agent
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Solution Overview
Problem
Current methods for producing highly-concentrated, low-viscosity, and high-purity silica sols for silicon wafer polishing and CMP processes face challenges such as viscosity increase, gelation, and contamination due to metal impurities, especially when using small silica particles, which affects production efficiency and storage stability.
Innovation Solution
A silica sol is produced using a dispersing agent with a degradation temperature and boiling point of 60° C. or higher, such as inorganic or organic acid salts, added to the reaction solution obtained by alkoxide method, followed by concentration and solvent substitution to achieve a silica concentration of 20 weight % or higher, maintaining low viscosity and preventing gelation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a dispersing agent with low degradation temperature (ammonium salts containing lower alkyl) is used to produce high-purity silica sol, then metal impurity contamination is avoided, but the dispersing agent degrades during heating process resulting in viscosity increase and gelation
Solution Approach 1:
The patent changes the key parameter of the dispersing agent from low degradation temperature (ammonium salts with lower alkyl) to high degradation temperature (degradation temperature ≥60°C). This parameter change allows the dispersing agent to withstand the heating process without degrading, thereby maintaining both high purity and viscosity stability throughout production and storage.
2Productivity
If silica concentration is increased to improve production efficiency and storage/transport efficiency, then production and transport costs are reduced, but viscosity increases and gelation occurs
Solution Approach 1:
The patent introduces a specific dispersing agent as an intermediary substance to mediate between silica particles at high concentrations. This dispersing agent prevents direct interaction and aggregation between silica particles, allowing the silica concentration to be increased to 20 wt% or higher while maintaining low viscosity and preventing gelation.
3Manufacturing precision
If small silica particles are used to achieve scratch-free polishing and high precision, then polishing quality is improved, but aggregation and gelation occur more easily causing viscosity increase
Solution Approach 1:
The patent uses a dispersing agent with degradation temperature ≥60°C as an intermediary to prevent aggregation of small silica particles. The dispersing agent creates a stable dispersion environment that allows small particles to remain separated and suspended, thereby maintaining both the polishing precision benefits and solution stability.
4Object-affected harmful factors
If alkali metal salts are used as dispersing agent to produce highly-concentrated silica sol, then viscosity is maintained at low level, but metal impurity contamination occurs
Solution Approach 1:
The patent changes the chemical composition parameter of the dispersing agent from alkali metal salts (which contain metal impurities) to compounds with degradation temperature ≥60°C that do not introduce metal contamination. This parameter change allows the dispersing agent to maintain low viscosity while avoiding metal impurity contamination, achieving both low viscosity and high purity.
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 resulting silica sol has long-term stability, low viscosity, and high purity, with metal impurity concentrations below 1 ppm, enhancing its use as a polishing agent for silicon wafers and CMP processes without contaminating materials.
Implementation Method 1
adding a dispersing agent at a specific concentration to a reaction solution or a solvent-substitution-concentrated-solution
Implementation Method 2
alkoxysilane is hydrolyzed and condensation-polymerized
Implementation Method 3
alkoxysilane is hydrolyzed and condensation-polymerized
Implementation Method 4
using a dispersing agent consisting of one or more compounds with both degradation temperature and boiling point of 60° C. or higher
Data Source
AI summary
This invention provides a high-purity, high-concentrated silica sol with long-term stability and low viscosity by preventing viscosity-increase after production, and method for producing the same. In one embodiment, the silica sol produced by an alkoxide method comprises at least a dispersing agent and silica, wherein the concentration of said dispersing agent is 10-3000 ppm with respect to the silica, wherein said dispersing agent may be an inorganic acid, inorganic acid salt, organic acid or organic acid salt whose degradation temperature and boiling point are both 60° C. or higher, wherein said silica sol has a silica concentration of 20% weight or higher.