Cerium Oxide Core-Shell Particles for Stable Low-Defect CMP
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Solution Overview
Problem
Existing cerium-based polishing compositions for chemical mechanical polishing (CMP) lack sufficient abrasive properties and are prone to defects due to particle size and distribution issues, requiring improved cerium-based particles with enhanced surface roughness and stability.
Innovation Solution
A process for producing cerium-based core-shell particles with a rough surface morphology, involving the formation of a cerium oxide shell on a cerium oxide core under controlled pH and temperature conditions, utilizing nitrate ions to enhance abrasive properties and maintain defectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polishing methods using alumina or silica particles are used, then the polishing process is simple, but the surface quality and precision of optical glass substrates deteriorate due to scratches and uneven surfaces
Solution Approach 1:
The invention uses composite particles consisting of a hard core material (alumina or silica) coated with a softer material (silica or fluorosilica). This composite structure allows the hard core to provide polishing power while the softer coating reduces scratches and improves surface quality, resolving the contradiction between polishing effectiveness and surface quality.
Solution Approach 2:
The invention changes the physical and chemical parameters of the polishing particles by controlling the core size (0.1-10 μm), shell thickness (1-100 nm), and material composition. These parameter changes enable precise control over polishing rate and surface quality, achieving high precision without excessive process complexity.
2Manufacturing precision
If multiple polishing steps with different particles are used to achieve high precision, then surface quality improves, but the number of steps and time required increases
Solution Approach 1:
The core-shell particles are designed to perform multiple functions simultaneously: the hard core provides cutting and material removal, while the softer shell protects the substrate and provides planarization. This multi-functionality allows a single polishing step to achieve both roughing and finishing, eliminating the need for multiple sequential steps and improving productivity.
Solution Approach 2:
The particle structure is segmented into distinct core and shell regions with different material properties. This segmentation allows each region to perform its specific function optimally while working together in a single polishing operation, achieving high precision without requiring multiple separate polishing steps.
3Productivity
If a slurry with high particle concentration is used to increase polishing rate, then productivity improves, but the slurry becomes unstable and particles aggregate
Solution Approach 1:
The invention changes the surface properties of the particles by coating them with silica or fluorosilica, which modifies the surface charge and interaction characteristics. This allows the use of higher particle concentrations (0.1-10 wt%) in the slurry while maintaining stability and preventing aggregation, thus improving polishing rate without compromising slurry stability.
Solution Approach 2:
The shell material is specifically selected to have different surface properties than the core material, creating local quality differences that improve slurry stability. The softer shell material provides steric and electrostatic stabilization, allowing high particle concentrations to be maintained without aggregation.
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 core-shell particles exhibit improved abrasive properties and stability, allowing for higher removal rates with reduced defects, suitable for CMP applications.
Implementation Method 1
where X is Si or Ge, Y1 to Y4 are independently selected from O, OH, or H, and R1 to R6 are independently selected from H, an alkyl group, or an alkoxy group
Implementation Method 2
the shell layer is formed by hydrolysis and condensation of organometallic compounds
Implementation Method 3
polishing of glass substrates... has been performed using alumina particles, silica particles, or the like as polishing particles
Data Source
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AI summary
The invention relates to cerium based core-shell particles having a core of cerium oxide optionally doped with at least one metal (M) and a shell consisting of a plurality of nanoparticles of cerium oxide optionally doped with at least one metal (M'), which can be the same or different from metal (M), formed on the surface of the core particle. The invention also relates to dispersions thereof in a liquid medium, to a process for producing the same and to the use of these particles and dispersions in polishing applications such as chemical mechanical polishing.