SiC Exfoliation on Reusable Substrates for Low-Defect Device Layers
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Solution Overview
Problem
The high cost and defect-related yield loss in wide bandgap semiconductor devices are exacerbated by the expensive and complex process of fabricating SiC substrates, which contribute significantly to the final device cost and reliability issues due to larger die sizes.
Innovation Solution
A method involving the use of a reusable silicon carbide substrate with patterned carbon regions and epitaxial lateral overgrowth (ELO/MELO) to form a Schottky Barrier Diode, allowing for multiple device fabrication cycles while maintaining low defect densities and reducing substrate contribution to the final die.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If SiC substrate fabrication process is used (vapor phase ingot growth, ingot cropping, wire sawing, grinding, polishing), then substrate quality is improved, but manufacturing cost increases and process complexity increases
Solution Approach 1:
The patent extracts and eliminates the most complex and costly steps from the traditional SiC substrate fabrication process. Specifically, it removes the vapor phase ingot growth, ingot cropping, wire sawing, grinding, and polishing steps by directly forming thin SiC substrate layers through epitaxial growth on reusable SiC substrates, thereby simplifying the manufacturing process while maintaining substrate quality
Solution Approach 2:
The patent changes the fundamental parameter of substrate thickness and formation method. Instead of growing thick ingots and mechanically processing them down to thin layers, the patent directly grows thin substrate layers (typically 3-10 micrometers) through controlled epitaxial growth, fundamentally altering the manufacturing approach from mechanical processing to chemical vapor deposition
2Manufacturing precision
If SiC substrate fabrication process is used (vapor phase ingot growth, ingot cropping, wire sawing, grinding, polishing), then substrate quality is improved, but manufacturing cost increases
Solution Approach 1:
The patent implements a substrate reuse strategy where SiC substrates are cleaned, re-coated with new epitaxial layers, and reused multiple times. This discards the traditional single-use substrate model and recovers the expensive SiC substrate material, significantly reducing per-device manufacturing cost while maintaining high substrate quality through controlled epitaxial growth
Solution Approach 2:
The patent effectively replaces the expensive, long-lived traditional SiC substrates with cheaper, short-lived epitaxial layers grown on reusable substrate templates. The thin epitaxial layers (3-10 micrometers) serve as disposable active layers that can be grown, processed, and peeled off, while the underlying substrate is reused, inverting the traditional value model
3Power
If larger die sizes are used for high current devices, then device performance is improved, but defect-related yield loss increases
Solution Approach 1:
The patent employs a peeling or delamination process that uses controlled mechanical or chemical forces to separate the finished device layer from the reusable substrate. This allows for the production of large-area devices with high current handling capability while maintaining low defect densities, as the controlled separation prevents defect propagation and enables substrate reuse for consistent 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
This approach reduces substrate costs and defect-related yield loss, enabling efficient and reliable production of wide bandgap semiconductor devices by allowing reuse of the silicon carbide substrate and minimizing defects through epitaxial lateral overgrowth.
Implementation Method 1
a laser is configured to heat the second material such that the plurality of silicon carbide regions in the patterned layer are vaporized or partially vaporized
Implementation Method 2
the plurality of silicon carbide regions in the patterned layer are vaporized or partially vaporized
Implementation Method 3
at least one silicon carbide epitaxial layer formed by epitaxial lateral overgrowth
Data Source
AI summary
A semiconductor substrate comprising a first epitaxial silicon carbide layer and a second silicon carbide epitaxial layer. At least one semiconductor device is formed in or on the second silicon carbide epitaxial layer. The semiconductor substrate is formed overlying a silicon carbide substrate having a surface comprising silicon carbide and carbon. An exfoliation process is used to remove the semiconductor substrate from the silicon carbide substrate. The carbon on the surface of the silicon carbide substrate supports separation. A portion of the silicon carbide substrate on the semiconductor substrate is removed after the exfoliation process. The surface of the silicon carbide substrate is prepared for reuse in subsequent formation of semiconductor substrates.