Cerium Oxide Polishing Suspension Monodispersity Segmentation
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Solution Overview
Problem
Current cerium oxide suspensions for polishing in the electronics industry face challenges in achieving high material removal rates while minimizing defects, as they often have non-monodisperse particles that are either too fine or too large, affecting their abrasive capacity and stability.
Innovation Solution
A suspension of cerium oxide particles with secondary particles averaging 200 nm or less, composed of monodisperse primary particles no larger than 100 nm with a standard deviation of 30% or less, is developed, using a process involving cerium III salt solutions, base reactions, heat treatment, and acidification to ensure stability and optimal particle size distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If particles are made finer to improve stability, then stability is improved, but abrasive capacity decreases
Solution Approach 1:
The suspension is segmented into two distinct particle populations: primary particles (10-50 nm) providing stability and secondary particles (50-200 nm) providing abrasion. This segmentation allows each size fraction to fulfill its specific function without compromising the other, resolving the contradiction between stability and abrasive capacity.
Solution Approach 2:
Different regions of the suspension exhibit different particle size characteristics tailored to specific functions. The primary particles create a stable colloidal suspension through their small size, while the secondary particles provide the necessary abrasive action. This local differentiation of particle properties allows simultaneous optimization of both stability and abrasive capacity.
2Productivity
If particles are made larger to improve abrasive capacity, then abrasive capacity is improved, but defectivity increases
Solution Approach 1:
The particle system is segmented such that only secondary particles (50-200 nm) contribute to abrasion, while primary particles (10-50 nm) remain too small to cause defects. This segmentation isolates the abrasive function from the defect-causing effect, allowing high abrasive capacity without increased defectivity.
Solution Approach 2:
The patent changes the particle size parameter to a specific range (50-200 nm for secondary particles) that is large enough to provide effective abrasion but small enough to avoid substrate damage. This precise parameter control resolves the contradiction between abrasive capacity and defectivity.
3Manufacturing precision
If particles are made monodisperse to improve performance, then polishing performance is improved, but manufacturing complexity increases
Solution Approach 1:
Rather than attempting to produce a single monodisperse population, the system segments particles into two distinct size classes with controlled distributions. This approach achieves functional monodispersity for each population while simplifying manufacturing, as each fraction can be produced through controlled precipitation or separation processes.
Solution Approach 2:
The suspension exhibits local monodispersity within each particle population. Primary particles maintain uniform size distribution optimized for stability, while secondary particles maintain uniform size distribution optimized for abrasion. This local quality control achieves overall performance improvement without requiring complex manufacturing processes.
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 suspension achieves improved monodispersity and stability, enhancing polishing performance by maintaining high abrasive capacity and reducing defects, thus meeting the industry's requirements for efficient material removal with minimal substrate damage.
Implementation Method 1
preparing a solution of a cerium III salt which additionally comprises cerium IV; this solution is brought into contact under an inert atmosphere with a base, whereby a precipitate is obtained
Implementation Method 2
the medium obtained in the preceding step is subjected to a heat treatment under an inert atmosphere
Implementation Method 3
successively, but in any order, acidification and washing of the medium thus obtained are carried out, whereby the suspension is obtained
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a suspension of cerium oxide particles in which the particles (secondary particles) have an average size not exceeding 200 nm, said secondary particles being comprised of primary particles having an average size not exceeding 100 nm with a standard deviation having a value not exceeding 30 % of the value of said average size. This suspension is prepared from a solution of a cerium-III salt, comprising cerium IV or hydrogen peroxide, which is brought into contact with a base in the presence of nitrate ions and in an inert atmosphere. The medium thus obtained is submitted to a thermal processing in an inert atmosphere, then acidified and scrubbed. The powder is obtained by drying and calcining of the suspension. The suspension and the powder can be used for polishing.