Thin Large-Diameter SiC Epitaxial Wafer for Shape Stability
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Solution Overview
Problem
Existing SiC epitaxial wafers face challenges in achieving a large diameter with thin thickness while minimizing triangular defects, which affect yield and device performance.
Innovation Solution
A SiC epitaxial wafer design with a diameter of 195 mm or more and a thickness of 460 μm or less, featuring a triangular defect density of 0.2 pieces/cm² or less, along with specific parameters for local thickness variation, site flatness, warp, bow, SORI, carrier concentration variation, and film thickness variation, to enhance device yield and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the diameter of the SiC epitaxial wafer is increased to produce more devices, then the number of devices per wafer increases, but the internal stress increases and shape changes occur during manufacturing
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the SiC substrate (460 μm or less) and the diameter (195 mm or more) to achieve optimal mechanical properties. By adjusting these dimensional parameters, the wafer maintains shape stability while enabling higher device density per wafer, thus resolving the contradiction between productivity and shape stability.
2Stability of the object's composition
If the thickness of the SiC substrate is increased to suppress shape change, then shape stability improves, but manufacturing cost increases and device resistance increases
Solution Approach 1:
The patent optimizes the substrate thickness parameter to 460 μm or less, which is sufficiently thin to reduce device resistance and manufacturing cost, yet sufficiently thick to maintain shape stability during processing. This precise parameter optimization resolves the contradiction between shape stability and device reliability.
3Reliability
If the thickness of the SiC substrate is reduced to lower cost and resistance, then manufacturing cost and device resistance decrease, but the substrate moves easily during vacuuming and rotation causing dust generation and triangular defects
Solution Approach 1:
The patent sets the substrate thickness to 460 μm or less but not thinner, establishing a lower bound that prevents excessive flexibility. This parameter threshold ensures the substrate remains rigid enough to prevent movement during vacuuming and rotation, thereby avoiding dust generation and triangular defects while maintaining low resistance and cost-effectiveness.
4Productivity
If the diameter of the SiC epitaxial wafer is increased, then more devices can be produced per wafer, but the wafer becomes more susceptible to movement and particle generation during processing
Solution Approach 1:
The patent combines large diameter (195 mm or more) with optimized thickness (460 μm or less) to achieve a specific aspect ratio that provides sufficient rigidity. This parameter combination allows the large-diameter wafer to maintain stability during vacuuming and rotation, preventing particle generation while maximizing device yield per wafer.
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 solution results in a SiC epitaxial wafer with high yield and low resistance, suitable for producing high-quality SiC devices with minimal defects, enabling efficient production of SiC devices that can withstand large electric currents.
Implementation Method 1
SiC epitaxial wafers are obtained by stacking a SiC epitaxial layer on the surface of a SiC substrate
Data Source
AI summary
An objective of the present invention is to provide a SiC epitaxial wafer with a large diameter, a thin thickness, and few triangular defects. A SiC epitaxial wafer includes a SiC substrate and a SiC epitaxial layer. The SiC substrate has a diameter of 195 mm or more and a thickness of 460 μm or less. The SiC epitaxial layer has a triangular defect density of 0.2 pieces/cm2 or less.