Colloidal Silica Dispersion Stability in Acidic Polishing
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Solution Overview
Problem
Existing silica particles lack sufficient dispersion stability under acidic conditions, which is necessary for chemical mechanical polishing processes in semiconductor manufacturing, leading to issues with polishing removal rate and particle adhesion.
Innovation Solution
The colloidal silica is formulated with a specific relaxation rate of 0.60 or more, measured by pulsed NMR at a silica particle concentration of 3 mass %, and a zeta potential of the surface silica particles in the pH range of 2 to 5 ranging from -10 to 10 mV, without using a modifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If silica particles are used under acidic conditions, then polishing process requirements are met, but dispersion stability deteriorates due to zeta potential approaching 0 mV
Solution Approach 1:
The invention changes the surface charge parameter of silica particles by controlling their production conditions to achieve a positive zeta potential in acidic conditions, rather than relying on negative charge. This parameter change allows the particles to maintain dispersion stability (through electrostatic repulsion) while being applicable to acidic polishing environments, resolving the contradiction between adaptability to acidic conditions and dispersion stability.
2Stability of the object's composition
If a modifier is used to improve dispersion stability under acidic conditions, then dispersion stability improves, but particle adhesion to polished object becomes problematic
Solution Approach 1:
The invention creates silica particles with controlled surface properties that naturally exhibit appropriate adhesion characteristics without requiring surface modification coatings. By controlling the surface charge and composition during particle formation, the particles achieve both dispersion stability and appropriate adhesion to polished objects, eliminating the need for modifiers that cause excessive adhesion.
3Stability of the object's composition
If strong electrostatic repulsion occurs between particles and polished object, then dispersion stability improves, but polishing removal rate decreases
Solution Approach 1:
The invention optimizes the surface charge parameter of silica particles to achieve a balanced state. By controlling the zeta potential to be positive but within a specific range, the particles maintain sufficient electrostatic repulsion for dispersion stability while having reduced repulsion toward the polished object surface, thereby maintaining adequate polishing removal rate.
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
This approach provides excellent dispersion stability of colloidal silica under acidic conditions, improving the polishing removal rate and reducing particle adhesion, thus enabling its use in advanced semiconductor manufacturing processes.
Implementation Method 1
Silica particles typically exhibit good dispersion stability under basic conditions. Under acidic conditions, however, the zeta potential approaches 0 mV; thus, maintaining dispersion stability is difficult, and particle aggregation easily occurs.
Implementation Method 2
the specific relaxation rate, as measured by pulsed MAR at a silica particle concentration of 3 mass %, is 0.60 or more
Data Source
AI summary
A colloidal silica comprising water and silica particles, wherein the specific relaxation rate, as measured by pulsed NMR at a silica particle concentration of 3 mass %, is 0.60 or more, and the zeta potential of the surface of the silica particles in the pH range of 2 to 5 is −10 to 10 mV.