Ceria Composite Particle Dispersion for High-Speed Semiconductor Polishing
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Solution Overview
Problem
Existing ceria-based composite particles for semiconductor polishing exhibit low polishing rates and surface defects due to low crystallinity, adhesion issues, and impurity contamination, leading to scratches and residual abrasive grains on the substrate.
Innovation Solution
A ceria-based composite fine particle dispersion with a specific structure, including amorphous silica core particles, crystalline ceria child particles, and a cerium-containing silica layer, optimized through a manufacturing process involving controlled temperature, pH, and oxidation-reduction potential to achieve high crystallinity, improved adhesion, and reduced impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional ceria particles are used for polishing, then polishing rate is improved, but surface accuracy deteriorates due to scratches and residual abrasive grains
Solution Approach 1:
The invention uses composite particles consisting of a silica core with ceria coating layer, combining the high polishing rate of ceria with the low scratch tendency of silica. The core-shell structure allows the ceria layer to perform chemical mechanical polishing while the silica core provides structural stability and reduces abrasive grain adhesion to the substrate.
Solution Approach 2:
The ceria coating layer is applied only on the surface of the silica core, creating local functional zones where the outer ceria layer provides high polishing rate while the inner silica core maintains low scratch generation. This local differentiation of material properties resolves the contradiction between polishing rate and surface accuracy.
2Productivity
If ceria particles with high crystallinity are used, then polishing rate is improved, but adhesion to substrate deteriorates
Solution Approach 1:
The composite structure combines crystalline ceria coating (for high polishing rate) with amorphous silica core (for good adhesion). The silica core acts as an adhesive base that prevents the crystalline ceria particles from detaching during polishing, while the ceria coating maintains its high polishing performance.
Solution Approach 2:
The invention changes the physical state parameter of the core material from crystalline to amorphous, which improves adhesion properties. The amorphous silica core provides better bonding characteristics compared to crystalline structures, while the ceria coating layer maintains its crystalline structure for high polishing rate.
3Ease of manufacture
If conventional manufacturing process is used, then production cost is reduced, but particle uniformity deteriorates
Solution Approach 1:
The invention prepares silica core particles with controlled size distribution before coating them with ceria. This preliminary preparation of uniform cores ensures that the final composite particles have consistent dimensions and properties. The pre-formed silica cores serve as templates that guide the subsequent ceria coating process, achieving uniform particle morphology.
Solution Approach 2:
The manufacturing process controls multiple parameters including pH value, temperature, and coating thickness to achieve uniform particle properties. By optimizing these parameters, the invention produces composite particles with consistent size, shape, and composition, improving particle uniformity while maintaining cost-effectiveness through a single-step coating process.
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 dispersion enables high-rate polishing of silica films and Si wafers with improved surface accuracy, reduced scratches, and low residual abrasive grains, while minimizing impurities, making it suitable for semiconductor substrates and circuit boards.
Implementation Method 1
the chemical components have a role in promoting polishing through oxidation or corrosion of a coating to be polished
Implementation Method 2
the abrasive grains have a role in polishing through a mechanical action
Implementation Method 3
mixing, with stirring, an aqueous solution of cerous nitrate with a base at such a ratio that the pH value ranges from 5 to 10, then rapidly heating the resulting mixture to a temperature of 70 to 100°C, and aging the mixture at that temperature
Implementation Method 4
the child particles are primarily composed of crystalline ceria
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
AI summary
The present invention addresses the problem of providing a silica composite particle dispersion capable of polishing silica films, Si wafers, or difficult-to-machine materials at high speed and of achieving high surface precision at the same time. This problem is solved by a ceria composite particle dispersion comprising ceria composite particles having an average particle size of 50 to 350 nm and having the features described below. Each ceria composite particle comprises a mother particle, a cerium-containing silica layer cn the surface thereof, and child particles dispersed inside the cerium-containing silica layer, the mother particles being amorphous silica-based and the child particles being crystalline ceria-based. The child particles have a coefficient cf variation (CV value) in a particle size distribution of 14 to 40%. The ceria composite particles have a mass ratio of silica to ceria cf 100:11-316. Only the crystal phase of ceria is detected when the ceria composite particles are subjected to X-ray diffraction. The average crystallite size of the crystalline ceria measured by subjecting the ceria composite particles to X-ray diffraction is 10 to 25 nm.