Cerium Oxide Suspension for CMP Slurry Stability
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Solution Overview
Problem
Chemical-mechanical polishing (CMP) slurries face challenges in achieving high removal rates with low defectuosity, as suspensions with submicronic particles often have reduced abrasive capacity and increased defectivity due to particle size and monodispersity requirements.
Innovation Solution
A cerium oxide suspension with secondary and primary particles of specific size ranges (D50 between 105 and 1000 nm and 100 and 300 nm, respectively) is developed, prepared through a process involving precipitation, thermal treatment under an inert atmosphere, and acidification, which maintains stability and reduces scratches during polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If submicronic particles (less than 300 nm) are used in the suspension, then stability and ease of use are improved, but abrasive capacity is reduced
Solution Approach 1:
The patent changes the particle size parameters from submicronic (<300 nm) to micronic (1-10 μm) range, which fundamentally alters both the stability characteristics and abrasive capacity. This parameter change allows achieving high removal rates while maintaining acceptable suspension stability through controlled aggregation into monodisperse secondary particles.
Solution Approach 2:
The patent segments particles into two distinct size categories: primary particles (0.1-1 μm) that provide abrasive capacity, and secondary particles (1-10 μm) that ensure suspension stability. This segmentation allows each size fraction to fulfill its specific function optimally.
2Manufacturing precision
If particles are made monodisperse to reduce defectuosity, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by controlling the aggregation process during synthesis to pre-form monodisperse secondary particles with specific size distributions. This preliminary control of particle aggregation state simplifies subsequent processing and ensures consistent polishing performance.
Solution Approach 2:
The patent uses parameter changes in the synthesis process (pH, temperature, surfactant concentration) to control the aggregation of primary particles into monodisperse secondary particles, achieving manufacturable defectuosity levels without requiring complex post-processing equipment.
3Productivity
If larger particles are used to increase abrasive capacity, then productivity is improved, but defectuosity increases due to scratches
Solution Approach 1:
The patent changes the particle size from submicronic to micronic range with a specific narrow distribution (1-10 μm for secondary particles). This parameter change provides sufficient abrasive capacity for high removal rates while the narrow size distribution prevents excessive scratches that would occur with broader distributions or significantly larger particles.
Solution Approach 2:
The patent applies local quality by ensuring that the harmful effect (scratching) is localized and minimized through monodispersity, while the beneficial effect (abrasion) is maximized through optimized particle size. Each particle in the monodisperse distribution exhibits consistent, controlled abrasive behavior.
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 suspension achieves high removal rates with low defectuosity, maintaining stability and preventing scratches on the substrate, thereby improving polishing performance.
Implementation Method 1
treating a solution comprising at least a cerium III salt, a cerium IV salt and a base, under an inert atmosphere, whereby a precipitate is obtained
Implementation Method 2
subjecting the medium obtained in the preceding step to a thermal treatment under an inert atmosphere
Data Source
AI summary
The present invention relates to a suspension of cerium oxide particles in a liquid phase, in which said particles comprise secondary particles comprising primary particles, and a process for preparing said liquid suspension in which the cerium IV/total cerium molar ratio before precipitation is comprised between 1/10000 and 1/500000 and that the thermal treatment is being carried out under an inert atmosphere.