Silicon Carbide Substrate Surface Stabilization via Sulfur and Carbon Control
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Solution Overview
Problem
Silicon carbide substrates for semiconductor devices face challenges in achieving a stabilized surface, which affects epitaxial growth and leads to reduced device yield due to impurity presence and native oxide formation, particularly in high-temperature and high-power applications.
Innovation Solution
A silicon carbide substrate with specific surface concentrations of sulfur, carbon, chlorine, oxygen, and metal impurities, along with controlled surface roughness and orientation, is developed to inhibit impurity adsorption and native oxide formation, thereby stabilizing the surface and improving epitaxial growth quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If surface treatment is applied to stabilize the silicon carbide substrate surface, then surface stability is improved, but impurity adsorption and native oxide formation still occur reducing device yield
Solution Approach 1:
The invention changes the chemical composition parameters of the silicon carbide substrate surface by controlling the concentration of sulfur atoms (6×10^19 to 2×10^21 atoms/cm²) and carbon atoms (3-25 at%). This parameter optimization creates a stable surface that resists impurity adsorption and native oxide formation, thereby improving both surface stability and device yield simultaneously
Solution Approach 2:
The invention creates a composite surface structure on the silicon carbide substrate by introducing sulfur and carbon elements in specific concentrations. This composite composition forms a protective surface layer that maintains stability while preventing harmful impurity adsorption and oxide formation, resolving the contradiction between surface stability and device reliability
2Quantity of substance
If the silicon carbide substrate surface is cleaned to remove impurities, then impurity concentration is reduced, but surface stability and epitaxial growth quality may be compromised
Solution Approach 1:
Instead of simply removing impurities, the invention optimizes the concentration parameters of specific elements (sulfur at 6×10^19 to 2×10^21 atoms/cm² and carbon at 3-25 at%). This controlled presence of certain impurities creates a stable surface composition that actually prevents adsorption of harmful impurities and native oxide formation, achieving better results than complete removal
3Ease of manufacture
If epitaxial growth is performed on a silicon carbide substrate with native oxide film, then device fabrication is simplified, but epitaxial layer quality is deteriorated
Solution Approach 1:
The invention performs preliminary surface stabilization by controlling sulfur and carbon concentrations before epitaxial growth. This pre-treatment creates a surface that inherently resists native oxide formation and impurity adsorption during the epitaxial process, allowing fabrication to proceed without complex cleaning steps while maintaining high epitaxial layer quality
Solution Approach 2:
By optimizing the chemical composition parameters (sulfur concentration: 6×10^19 to 2×10^21 atoms/cm², carbon concentration: 3-25 at%), the invention creates surface conditions that enable direct epitaxial growth without requiring complete oxide removal, thus simplifying manufacturing while preserving epitaxial layer quality
4Stability of the object's composition
If sulfur and carbon impurities are present on the silicon carbide substrate surface, then surface stability is improved, but excessive amounts inhibit epitaxial growth
Solution Approach 1:
The invention precisely controls the concentration parameters of sulfur (6×10^19 to 2×10^21 atoms/cm²) and carbon (3-25 at%) on the silicon carbide substrate surface. This optimization ensures sufficient impurity presence to stabilize the surface and prevent harmful adsorption, while maintaining amounts below thresholds that would inhibit epitaxial growth, thus resolving the contradiction between stability and growth quality
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 controlled impurity presence and surface characteristics enhance the yield and quality of semiconductor devices by reducing leakage current and improving channel mobility, making them suitable for high-power applications.
Implementation Method 1
the presence of certain amounts of sulfur atoms and carbon atoms as an impurity in the surface of the silicon carbide substrate, oxidation of the surface and an increase in impurities are suppressed
Implementation Method 2
when a native oxide film is formed on the surface of the silicon carbide substrate from oxygen in an atmosphere
Data Source
AI summary
A silicon carbide substrate has a first main surface, and a second main surface opposite to the first main surface. A region including at least one main surface of the first and second main surfaces is made of single-crystal silicon carbide. In the one main surface, sulfur atoms are present at not less than 60×1010 atoms/cm2 and not more than 2000×1010 atoms/cm2, and carbon atoms as an impurity are present at not less than 3 at % and not more than 25 at %. Thereby, a silicon carbide substrate having a stable surface, a semiconductor device using the substrate, and methods for manufacturing them can be provided.