Silicon Carbide Epitaxial Substrate for Triangular Recess Control
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Solution Overview
Problem
Existing silicon carbide epitaxial substrates face challenges in achieving high yield due to defects such as triangular-shaped recesses and stacking faults, which affect the performance and reliability of silicon carbide semiconductor devices.
Innovation Solution
The silicon carbide epitaxial substrate is designed with a triangular-shaped recess on its surface, having specific dimensions and polytype differences at the recess bottom, and is manufactured using a controlled silane flow rate to minimize defects like stacking faults and recesses, ensuring a low area density and improved substrate quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional silicon carbide epitaxial growth is used, then manufacturing process is simple, but triangular-shaped defects and stacking faults occur reducing yield
Solution Approach 1:
The patent applies preliminary action by forming a buffer layer with controlled polytype (3C-SiC) before the main epitaxial growth of 4H-SiC. This preliminary layer prevents the formation of triangular-shaped defects and stacking faults during subsequent growth, thereby improving epitaxial layer quality and device yield without complicating the overall manufacturing process
Solution Approach 2:
The patent utilizes parameter changes by controlling the silane flow rate during epitaxial growth to maintain a gradient (decreasing flow rate with increasing thickness). This parameter control prevents polytype transitions and defect formation, improving both manufacturing precision and device yield while maintaining process simplicity
2Productivity
If high silane flow rate is used for fast growth, then productivity increases, but triangular-shaped recesses and stacking faults increase reducing reliability
Solution Approach 1:
The patent applies periodic action by varying the silane flow rate during different stages of epitaxial growth. The flow rate is highest during initial growth and progressively decreases, creating a time-dependent control pattern that maintains high overall productivity while preventing defect formation at critical growth stages
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the silane flow rate parameter throughout the growth process. This controlled variation maintains high average growth rate for productivity while preventing the formation of triangular-shaped recesses and stacking faults that occur at constant high flow rates
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 enhances the yield and reliability of silicon carbide semiconductor devices by reducing defects, thereby improving the manufacturing process efficiency and device performance.
Implementation Method 1
a silicon carbide epitaxial layer located on the silicon carbide substrate
Data Source
AI summary
A silicon carbide epitaxial substrate has a silicon carbide substrate and a silicon carbide epitaxial layer. The silicon carbide epitaxial layer has a first main surface. A recess is formed in the first main surface. As viewed in a direction perpendicular to the first main surface, an outer shape of the recess is a triangular shape. A depth of the recess in the direction perpendicular to the first main surface is 100 nm or more. A length of the recess in a direction obtained by projecting a<11-20> direction onto the first main surface is 80 μm or less. An area density of the recesses in the first main surface is 0.1/cm2 or less. A polytype of silicon carbide of a bottom surface of the recess is different from a polytype of silicon carbide of the silicon carbide epitaxial layer.