Silicon Carbide Epitaxial Substrate Exfoliation for Lower Defect Cost
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Solution Overview
Problem
The high cost of wide bandgap semiconductor devices is predominantly due to the expensive substrate materials, particularly silicon carbide substrates, which have not seen a reduction in cost despite improved quality, and defects in these substrates lead to yield loss and potential reliability issues in high-current devices.
Innovation Solution
The method involves creating an array of micro-voids in the silicon carbide substrate, filling these voids with a carbonized polymer layer, and then growing an epitaxial layer using merged epitaxial lateral overgrowth (MELO) to form a Schottky Barrier Diode, allowing for the exfoliation of the device from the substrate, thereby reducing substrate costs and maintaining low defect densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional substrate fabrication processes are used, then substrate quality is maintained, but substrate cost remains high
Solution Approach 1:
The patent extracts and removes the expensive silicon carbide substrate after the epitaxial layer has been grown. The substrate is no longer needed once it has served its purpose as a growth platform, allowing cost reduction while maintaining device quality.
Solution Approach 2:
The substrate is discarded after use in the epitaxial growth process. The expensive substrate material is consumed only for the purpose of growing the active layer, and then removed, converting a recurring cost into a one-time consumable.
2Power
If larger die sizes are used for high current devices, then device capability is improved, but defect impact increases
Solution Approach 1:
By removing the substrate after growth, the patent eliminates the source of substrate-related defects from the final device structure. This extraction of the substrate prevents defect propagation to larger die areas, enabling high-current applications without proportional yield loss.
Solution Approach 2:
The patent segments the fabrication process into substrate preparation, epitaxial growth, and substrate removal phases. This segmentation allows the substrate to be optimized for growth purposes while the final device structure is optimized for performance, decoupling substrate quality constraints from device performance requirements.
3Ease of manufacture
If substrate fabrication complexity is reduced, then manufacturing cost decreases, but substrate quality may deteriorate
Solution Approach 1:
The patent employs the substrate as a disposable, low-cost consumable item for the epitaxial growth process. Rather than investing in expensive, high-quality substrates that must be reused or carefully managed, a simpler, cheaper substrate is used once and then discarded, eliminating the need for complex quality maintenance.
Solution Approach 2:
The substrate is prepared and processed beforehand specifically for the epitaxial growth function. Any necessary quality attributes are established during substrate fabrication before it reaches the epitaxial reactor, allowing simple substrates to be adequately prepared for their specific purpose without requiring inherently complex substrate materials.
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 the substrate contribution to the final device cost, enhances yield by minimizing defect impact, and maintains performance parameters, enabling the production of cost-effective wide bandgap semiconductor devices with improved reliability.
Implementation Method 1
the polymer layer is pyrolyzed to form a carbonized polymer layer
Implementation Method 2
growing an epitaxial layer using merged epitaxial lateral overgrowth (MELO)
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.