Cerium CMP Slurry Chemistry for Fast Polishing With Fewer Scratches
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Solution Overview
Problem
Existing CMP techniques fail to efficiently remove elemental mercury (Hg0) from flue gas and oxidized mercury (Hg2+) from waste liquid, with activated carbon injection technology being costly and its mercury removal efficiency is affected by NOx and SO2.
Innovation Solution
Utilization of metal sulfides (e.g., FeS2, CuS, CuS, CuFeS2) as mercury removal adsorbents, which contact with flue gas and waste liquid, adsorbing and converting Hg0 from flue gas and Hg2+ from waste liquid into stable mercury sulfide compounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If silica-based polishing liquid is used for high polishing rate, then polishing rate is improved, but polishing scratches increase causing defects
Solution Approach 1:
The patent changes the material parameter of abrasive grains from silica-based to cerium-based particles, which fundamentally alters the polishing mechanism. Cerium-based particles provide both high polishing rate and reduced scratching compared to silica-based particles, resolving the contradiction between productivity and harmful effects.
Solution Approach 2:
The patent uses composite polishing liquid containing cerium-based particles combined with specific additives (polymer dispersants and pH buffers). This composite formulation enhances the performance of cerium-based particles, maintaining high polishing rate while controlling scratches through the synergistic effect of multiple components.
2Object-affected harmful factors
If cerium-based polishing liquid is used to reduce polishing scratches, then polishing scratches are reduced, but polishing rate decreases
Solution Approach 1:
The patent optimizes parameters of cerium-based polishing liquid including particle size distribution (0.1-10 μm), concentration (1-10 wt%), and pH (8-11). These parameter adjustments maximize the polishing rate of cerium-based particles while maintaining their low scratching characteristic, thus resolving the contradiction with silica-based liquids.
Solution Approach 2:
The patent introduces polymer dispersants and pH buffer additives as intermediaries that enhance the performance of cerium-based particles. These additives improve particle dispersion, stability, and chemical reactivity, enabling cerium-based particles to achieve higher polishing rates without increasing scratches.
3Object-affected harmful factors
If abrasive grains with negative zeta potential are used for electrostatic repulsion, then abrasive grain remaining is reduced, but polishing rate decreases due to repulsion
Solution Approach 1:
The patent adjusts the zeta potential of cerium-based particles to a specific negative range (-30 to -70 mV) through pH control and dispersant addition. This optimized negative potential provides sufficient electrostatic repulsion to prevent particle remaining on the wafer surface while maintaining adequate polishing rate through chemical affinity between cerium particles and silicon oxide.
Solution Approach 2:
The patent utilizes the natural negative zeta potential characteristic of cerium-based particles and enhances it through additives, creating a polishing system that copies the beneficial low-remaining property while compensating for the potential rate reduction through chemical mechanism optimization.
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
Achieves efficient, cost-effective, and environmentally friendly simultaneous removal of Hg0 from flue gas and Hg2+ from waste liquid, avoiding secondary pollution and reducing operational costs.
Implementation Method 1
metal sulfides (e.g., FeS2, CuS, CuS, CuFeS2) as mercury removal adsorbents, which contact with flue gas and waste liquid, adsorbing and converting Hg0 from flue gas and Hg2+ from waste liquid into stable mercury sulfide compounds
Implementation Method 2
adsorbing and converting Hg0 from flue gas and Hg2+ from waste liquid into stable mercury sulfide compounds
Data Source
AI summary
A polishing liquid for CMP, containing: abrasive grains; an additive; and water, in which the abrasive grains include cerium-based particles, a zeta potential of the abrasive grains is negative, the additive includes (A1) a 4-pyrone-based compound represented by General Formula (1) below, and a pH is 5.0 or more. A polishing liquid for CMP, containing: abrasive grains; an additive; and water, in which the abrasive grains include cerium-based particles, a zeta potential of the abrasive grains is negative, the additive includes (A2) a picolinic acid compound, and a pH is 5.0 or more.[In the formula, X11, X12, and X13 are each independently a hydrogen atom or a monovalent substituent.]