Silicon Carbide Substrate Defect Control for Smoother Epitaxial Layers
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Solution Overview
Problem
Existing silicon carbide substrates face challenges in maintaining surface roughness during the formation of epitaxial layers, as blind scratches and dislocations can lead to deterioration of the surface quality, which is not effectively addressed by current manufacturing methods.
Innovation Solution
A silicon carbide substrate is manufactured using chemical mechanical polishing and etching with an aqueous alkali solution at elevated temperatures, specifically using a potassium hydroxide or sodium hydroxide solution, to reduce the area density of blind scratches and dislocations, thereby minimizing surface roughness deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical mechanical polishing is performed to reduce surface roughness, then surface smoothness is improved, but blind scratches are generated on the substrate surface
Solution Approach 1:
The patent converts the harmful blind scratches generated during chemical mechanical polishing into a beneficial feature by intentionally creating controlled blind scratches with specific density ratios. The method uses the polishing process to generate blind scratches, then employs etching to create a pattern where blind scratch density accounts for 70-90% of total defect density, transforming the previously harmful random scratches into a controlled defect structure that actually improves epitaxial growth quality
Solution Approach 2:
The patent changes the parameters of the blind scratches by controlling their density ratio relative to other defects. By adjusting the blind scratch density to account for 70-90% of total defect density through controlled etching processes, the patent transforms the quality of defects from harmful to beneficial, enabling better epitaxial layer formation while maintaining acceptable surface roughness
2Manufacturing precision
If blind scratches and dislocations are reduced to improve surface quality, then surface roughness is improved, but epitaxial layer formation is hindered
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of defects on the substrate surface. By controlling blind scratch density to account for 70-90% of total defect density in specific regions, the patent creates localized defect patterns that promote epitaxial layer formation in those areas while maintaining overall surface quality, thus resolving the contradiction between surface quality and epitaxial formation
3Manufacturing precision
If etching is performed to remove blind scratches, then surface roughness is improved, but substrate damage increases
Solution Approach 1:
The patent applies partial action by performing etching to create blind scratches rather than completely removing all defects. The etching process is controlled to generate blind scratches at a specific density ratio (70-90% of total defects) rather than attempting to eliminate all surface imperfections, thus improving surface quality without excessive substrate damage
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 method effectively suppresses the deterioration of surface roughness in silicon carbide epitaxial layers by reducing the area density of defects, resulting in improved surface quality and reduced haze values and arithmetic average roughness.
Implementation Method 1
The silicon carbide single-crystal substrate is etched using a solution under a temperature condition of 70° C. or higher. The solution contains an aqueous alkali solution.
Implementation Method 2
Chemical mechanical polishing is performed on a silicon carbide single-crystal substrate. The silicon carbide single-crystal substrate is etched using a solution under a temperature condition of 70° C. or higher.
Implementation Method 3
Chemical mechanical polishing is performed on a silicon carbide single-crystal substrate.
Data Source
AI summary
A silicon carbide substrate includes a first main surface, a second main surface, and an outer peripheral surface. When a defect, in the first main surface, observed using a mirror electron microscope while irradiating the first main surface with an ultraviolet ray is a first defect and a defect, in the first main surface, observed using molten potassium hydroxide is a second defect, a value obtained by dividing an area density of the first defect by an area density of the second defect is more than 0.9 and less than 1.2. The first defect consists of a first blind scratch, a first basal plane dislocation spaced apart from the first blind scratch, a second basal plane dislocation in contact with the first blind scratch, and a second blind scratch spaced apart from each of the first basal plane dislocation and the second basal plane dislocation.