Composite Polishing Particles for Hard Substrate Planarization
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Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) methods for hard substrates face challenges in achieving high removal rates while minimizing surface and sub-surface damage, as larger hard particles increase polishing rates but also cause significant damage, requiring multiple steps with progressively smaller particles.
Innovation Solution
The use of composite particles comprising a plurality of hard particles on a soft-core particle, along with optional chemistries, in a slurry to enhance the removal rate of hard substrate materials during CMP while reducing damage, where the hard particles have a higher Mohs or Vickers hardness than the soft-core particles, and the addition of coatings and oxidizers to improve chemical action and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If larger hard particles are used in CMP, then polishing rate increases, but surface and sub-surface damage increases
Solution Approach 1:
The patent uses composite particles consisting of a soft core (alumina, silica, or boron carbide) coated with hard particles (diamond, cubic boron nitride, or silicon carbide). The soft core provides cushioning to reduce subsurface damage while the hard outer layer maintains high polishing rate, resolving the contradiction between productivity and damage reduction.
Solution Approach 2:
The patent changes the structural parameters of the polishing particles from solid hard particles to composite particles with soft cores and hard coatings. This parameter change allows the particles to maintain hardness for efficient material removal while the soft core reduces the harmful mechanical impact on the substrate.
2Manufacturing precision
If multiple CMP steps with progressively smaller particles are used, then surface finish improves, but process complexity and time increase
Solution Approach 1:
The patent combines the functions of multiple polishing steps (material removal and surface finishing) into a single step using composite particles. The hard coating removes material efficiently while the soft core simultaneously protects against damage, eliminating the need for sequential steps with different particle sizes.
Solution Approach 2:
The composite particles perform multiple functions simultaneously: the hard outer layer provides high material removal rate while the soft inner core provides cushioning to prevent subsurface damage. This multi-functionality allows a single polishing step to achieve both roughness reduction and surface finish improvement.
3Object-affected harmful factors
If multiple CMP steps are used, then damage is reduced, but loss of time increases
Solution Approach 1:
The patent merges the damage-reduction function of multiple steps into a single step by using composite particles with soft cores. The soft core provides continuous cushioning throughout the polishing process, preventing subsurface damage while maintaining high material removal rate, thus reducing total process time.
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
This approach results in higher polishing rates and lower surface and sub-surface damage for hard substrates like sapphire, diamond, and zirconia, with improved dispersability and stability of the slurry, allowing for more efficient planarization without the need for multiple steps.
Implementation Method 1
CMP utilizes a slurry generally including water, an oxidizer and particles for selective removal of material from substrates
Implementation Method 2
CMP utilizes a slurry generally including water, an oxidizer and particles for selective removal of material from substrates
Data Source
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AI summary
A chemical mechanical polishing (CMP) includes providing a slurry including composite particles dispersed in a water-based carrier that comprise a plurality of hard particles on an outer surface of a soft-core particle. The hard particles have a Mohs hardness at least 1 greater than a Mohs hardness of the soft core particle and/or a Vickers hardness at least 500 Kg/mm2 greater than the soft-core particle. A substrate having a substrate surface with a hardness greater than a Mohs number of 6 or a Vickers hardness greater than 1,000 kg/mm2 is placed into a CMP apparatus having a rotating polishing pad, and CMP is performed with the rotating polishing pad and the slurry to polish the substrate surface.