Single Crystal Silicon Carbide Substrate Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for manufacturing single crystal silicon carbide substrates with a 4H polytype crystal structure result in significant variations in nitrogen atom concentration and dislocation density due to the coexistence of facet and non-facet regions, leading to in-plane variations in physical properties.
Innovation Solution
A single crystal silicon carbide substrate with a 4H-polytype crystal structure is manufactured by doping nitrogen atoms at a concentration of more than 1×10^16/cm^3, ensuring only one type of region (either facet or non-facet) is present on the surface, eliminating boundaries and reducing dislocation density, and having a circular main surface to minimize warp.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If both spiral growth and step-flow growth take place during crystal growth, then high-quality single crystal can be obtained, but significant variation in nitrogen atom concentration and dislocation density occurs between facet and non-facet regions
Solution Approach 1:
The invention segments the crystal growth process by separating the facet region and non-facet region into distinct zones. By controlling the growth conditions such that only one type of region (either facet or non-facet) is formed, the patent eliminates the coexistence of regions with different nitrogen concentrations and dislocation densities, thereby achieving uniform physical properties throughout the substrate.
Solution Approach 2:
The invention applies local quality control by creating a uniform crystal structure throughout the entire substrate area. By ensuring that the entire substrate consists of either facet or non-facet regions (but not both), the patent achieves consistent nitrogen atom concentration and dislocation density across the whole substrate, eliminating local variations.
2Reliability
If nitrogen atoms are introduced at high concentration to achieve high-quality 4H-type single crystal, then reproducibility improves, but in-plane variation in nitrogen atom concentration increases due to region-specific accumulation
Solution Approach 1:
The invention segments the substrate into a single uniform region type, preventing the formation of multiple zones with different nitrogen concentrations. By controlling growth conditions to produce only facet or only non-facet regions, the patent eliminates the spatial variation in nitrogen concentration that would otherwise occur within the substrate plane.
3Productivity
If both facet region and non-facet region coexist on the substrate, then crystal growth can proceed efficiently, but warp of the substrate increases due to lattice constant differences
Solution Approach 1:
The invention segments the crystal structure to exclude the coexistence of facet and non-facet regions. By controlling the growth process to produce a substrate with uniform region type throughout, the patent eliminates the lattice constant variations that cause substrate warp, thereby improving compositional stability and flatness.
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 suppresses nitrogen atom concentration and dislocation density variations, achieving a ratio of less than 1.5 for nitrogen concentration and less than 5 for dislocation density, while preventing warp and maintaining high symmetry, thus enhancing the substrate's physical properties.
Implementation Method 1
nitrogen atoms doped as a conduction impurity with an atomic concentration of more than 1×10^16/cm³
Implementation Method 2
a source material made of silicon carbide is sublimated by heating, and supplied onto a seed crystal made of single crystal silicon carbide, to grow single crystal silicon carbide on this seed crystal
Data Source
AI summary
A single crystal silicon carbide substrate has a 4H-polytype crystal structure, has with nitrogen atoms doped as a conduction impurity with an atomic concentration of more than 1×1016/cm3, and has a main surface containing a circle having a diameter of 5 cm. The single crystal silicon carbide substrate includes only one of a facet region and a non-facet region. Thus, variation in nitrogen atom concentration in the single crystal silicon carbide substrate can be suppressed.