SiC Epitaxial Substrate Exfoliation for Lower Defect Device Layers
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Solution Overview
Problem
The high cost of wide bandgap semiconductor devices is dominated by the expensive substrate, and defects in larger die sizes lead to yield loss and reliability issues, necessitating a method to reduce substrate contribution while maintaining yield and performance.
Innovation Solution
A method involving the use of a silicon carbide substrate with patterned hard mask and micro-voids filled with a polymer or carbonized layer, followed by epitaxial lateral overgrowth to form a single crystal layer that can be exfoliated, reducing substrate reliance and defect density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SiC substrate fabrication processes (vapor phase ingot growth, cropping, wire sawing, grinding, polishing) are used to produce high-quality substrates, then substrate quality and defect reduction are improved, but manufacturing cost and process complexity increase significantly
Solution Approach 1:
The patent extracts and eliminates unnecessary substrate processing steps (cropping, wire sawing, grinding, polishing) by directly growing epitaxial layers on as-grown SiC substrates. This extraction principle removes complex and costly processes while maintaining substrate quality for device fabrication.
Solution Approach 2:
The patent performs preliminary epitaxial layer growth directly on the as-grown substrate before any substrate processing. By growing the active device layer first on the raw substrate, the method eliminates the need for subsequent substrate preparation steps, reversing the conventional sequence to simplify the overall process.
2Power
If larger die sizes are used to increase device output, then device power handling capability is improved, but defect density impact and yield loss increase
Solution Approach 1:
The patent changes the substrate defect parameter by using as-grown SiC substrates with controlled defect characteristics rather than heavily processed substrates. This parameter change in substrate quality allows larger die sizes to be fabricated with acceptable yield, as the epitaxial growth process on as-grown substrates produces fewer defects that would propagate through large-area devices.
3Ease of manufacture
If substrate processing steps are eliminated to reduce cost, then manufacturing cost decreases, but substrate quality and defect density may worsen
Solution Approach 1:
The patent inverts the conventional manufacturing approach by growing epitaxial layers on as-grown substrates before any substrate processing. This inversion demonstrates that substrate processing steps can be eliminated without compromising device quality, as the critical epitaxial growth occurs on the raw substrate surface which is sufficient for high-quality layer formation.
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 cost and defect density, enabling efficient fabrication of high-quality semiconductor devices with improved yield and reliability.
Implementation Method 1
the plurality of micro-voids are filled with a polymer or carbonized layer
Implementation Method 2
followed by epitaxial lateral overgrowth to form a single crystal layer
Data Source
AI summary
An epitaxial silicon carbide substrate comprises a first epitaxial silicon carbide layer and at least a second silicon carbide epitaxial layer. A plurality of devices are formed in or overlying the second silicon carbide epitaxial layer. The epitaxial silicon carbide substrate is formed overlying a reuseable silicon carbide substrate. An exfoliation layer is at or underlies a surface of the reuseable silicon carbide substrate. The exfoliation layer comprises silicon carbide and carbon. In one embodiment a plurality of trenches is formed in the surface of the reuseable silicon carbide substrate. The layer of carbon is formed in or below the plurality of trenches. An exfoliation process comprises thermal or mechanical processes to separate the reuseable silicon carbide substrate from the epitaxial silicon carbide substrate. The surface of the reuseable silicon carbide substrate is prepared so the reuseable silicon carbide substrate can be reused.