Silicon Carbide Substrate Polishing via Oxidant-Driven Chemical Removal
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Solution Overview
Problem
Existing polishing methods for silicon carbide and gallium nitride single-crystal substrates face challenges in achieving high polishing rates and smooth surfaces due to the high hardness and chemical stability of these materials, leading to low efficiency and surface damage from abrasive grains.
Innovation Solution
A polishing method using a polishing liquid with a redox potential of 0.5 V or more, containing a transition metal oxidant like permanganate, and water, but without abrasive grains, which forms an oxide layer on the substrate surface for mechanical removal, ensuring a high polishing rate and smoothness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If diamond abrasive grains are used for mechanical polishing of silicon carbide single crystal, then the surface can be flattened, but minute scratches are introduced and the surface smoothness is insufficient
Solution Approach 1:
The patent replaces the mechanical polishing system using diamond abrasive grains with a chemical mechanical polishing system using a polishing composition containing colloidal silica and vanadate. This substitution eliminates the scratching caused by hard diamond particles while maintaining the ability to flatten and smooth the silicon carbide surface through a combination of chemical oxidation and gentle mechanical removal.
Solution Approach 2:
The patent changes the parameters of the polishing system by using a polishing composition with specific pH (4-9) and containing colloidal silica particles of controlled size (0.01-10 μm) along with vanadate. These parameter changes enable effective polishing of silicon carbide without introducing scratches, achieving both flatness and high surface smoothness.
2Manufacturing precision
If conventional polishing compositions are used, then surface smoothness can be improved, but polishing rate is low and polishing time is excessive
Solution Approach 1:
The patent uses a composite polishing composition containing colloidal silica, vanadate, and water. This composite formulation combines the gentle polishing action of colloidal silica with the catalytic effect of vanadate, achieving both high surface smoothness and improved polishing rate compared to conventional single-component polishing compositions.
Solution Approach 2:
The patent employs vanadate as a strong oxidizing agent in the polishing composition. The vanadate accelerates the oxidation of silicon carbide surface, enabling faster material removal while maintaining surface smoothness. This accelerates the polishing rate without sacrificing the quality of the finished surface.
3Productivity
If abrasive grains are used for polishing, then material removal can be achieved, but aggregation of abrasive grains occurs and causes instability
Solution Approach 1:
The patent uses colloidal silica particles that are suspended in water and do not aggregate like solid abrasive grains. These particles can be continuously supplied and replaced, providing stable and consistent polishing action without the aggregation problems that plague reusable abrasive grain systems.
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 method enables high-speed, stable polishing of hard non-oxide single-crystal substrates with improved surface smoothness and flatness, preventing scratches and aggregation issues associated with abrasive grains.
Implementation Method 1
the polishing liquid comprises: an oxidant whose redox potential is 0.5 V or more and which contains a transition metal; and water
Data Source
AI summary
There is provided a polishing method for polishing a non-oxide single-crystal substrate such as a silicon carbide single-crystal substrate at a high polishing rate to obtain a high-quality surface that is smooth and excellent in surface properties. This polishing method is a method of supplying a polishing liquid to a polishing pad not including abrasive grains to bring a surface to be polished of the non-oxide single-crystal substrate and the polishing pad into contact with each other and polishing the surface to be polished by a relative movement between them, the method characterized in that the polishing liquid comprises: an oxidant whose redox potential is 0.5 V or more and which contains a transition metal; and water, and does not contain abrasive grains.