CMP Silica Abrasives with High Density for Scratch Reduction
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Solution Overview
Problem
The chemical mechanical polishing (CMP) method for semiconductor devices faces challenges with scratches during polishing, leading to decreased yield and productivity due to the limitations of existing abrasive materials like fumed silica and colloidal silica, which either cause scratches or have low polishing efficiency.
Innovation Solution
A silica for CMP with specific properties is developed, including a BET specific surface area of 40-180 m2/g, a particle density of 2.24 g/cm3 or more, a coefficient of variation in primary particle diameter of 0.40 or less, and a fractal shape parameter αmax value of 2.9 or more, produced through a flame hydrolysis reaction, to reduce scratches while maintaining high polishing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fumed silica is used as abrasive grains, then polishing efficiency is improved, but scratches increase
Solution Approach 1:
The invention changes the particle density parameter of silica abrasive grains from conventional values (1.8-2.2 g/cm³) to a higher range (2.2-2.6 g/cm³). This parameter change fundamentally alters the mechanical properties of the abrasive grains, making them harder and more resistant to deformation during polishing, thereby reducing scratches while maintaining high polishing efficiency
Solution Approach 2:
The invention creates a composite abrasive grain structure by controlling the aggregation of primary silica particles into secondary particles with specific density and size distributions. This composite structure combines the high surface area of fine particles with the mechanical strength of denser aggregated structures, achieving both high polishing efficiency and low scratch generation
2Object-affected harmful factors
If colloidal silica is used as abrasive grains, then scratches are reduced, but polishing efficiency decreases
Solution Approach 1:
The invention fundamentally changes the particle density parameter from the low-density colloidal silica structure to a high-density aggregated structure (2.2-2.6 g/cm³). This parameter change restores the mechanical strength and cutting ability while maintaining the controlled size distribution that prevents scratch formation
Solution Approach 2:
The invention creates local quality differences within the abrasive grain structure by forming aggregated particles with specific internal structures. The primary particles maintain high surface area for chemical reaction, while the aggregated structure provides mechanical strength, creating different functional zones within the same abrasive grain
3Productivity
If cerium oxide is used as abrasive grains, then polishing efficiency is improved, but scratches increase due to poor dispersion stability
Solution Approach 1:
The invention replaces cerium oxide (a rare earth material with high cost and environmental concerns) with silica, a abundant and environmentally friendly material. By optimizing the particle density and size distribution of silica, the invention achieves comparable polishing efficiency without the scratch problems associated with cerium oxide
Solution Approach 2:
The invention changes the material composition from cerium oxide to silica, and simultaneously optimizes the particle density parameter to 2.2-2.6 g/cm³. This dual parameter change (material composition and physical property) achieves the desired balance between polishing efficiency and scratch reduction
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 silica effectively reduces scratches and ensures a high polishing rate, improving the yield and productivity of the CMP process by optimizing particle density and size distribution, and reducing impurity content.
Implementation Method 1
an abrasive (aqueous dispersion) in which fine particles, such as silica or alumina, are mixed and dispersed in an alkaline or acidic chemical aqueous solution
Implementation Method 2
produced through a flame hydrolysis reaction
Data Source
AI summary
To reduce scratches during polishing while ensuring an appropriately high polishing rate, provided are a silica for CMP satisfying the following (A) to (C), an aqueous dispersion using a silica for CMP, and a method of producing a silica for CMP: (A) a BET specific surface area of 40 m2/g or more and 180 m2/g or less; (B) a particle density measured by a He-gas pycnometer method of 2.24 g/cm3 or more; and (C) a coefficient of variation in primary particle diameter calculated by TEM/image analysis of 0.40 or less.