GaN-on-SiC Semiconductor Substrate for Crystal Quality at Lower Cost
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Solution Overview
Problem
The challenge in semiconductor manufacturing is achieving high-quality epitaxial layers for RF components and power devices while balancing cost, particularly due to the lattice mismatch between silicon and gallium nitride, and the high cost of silicon carbide substrates.
Innovation Solution
A semiconductor substrate is developed with a high-resistivity silicon carbide layer and a gallium nitride epitaxial layer, where the gallium nitride layer is grown on the silicon carbide layer with specific thickness and crystal quality parameters, and a damaged layer is formed using a laser for separation, allowing for the reuse of silicon carbide substrates and reducing material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon substrates are used to grow gallium nitride, then the cost is reduced, but lattice mismatch problems occur affecting crystal quality
Solution Approach 1:
A silicon carbide buffer layer is introduced as an intermediary between the silicon substrate and the gallium nitride epitaxial layer. This buffer layer serves as a transition medium that reduces the lattice mismatch between silicon and gallium nitride, enabling high-quality crystal growth while maintaining cost advantages of silicon substrates.
Solution Approach 2:
The patent employs a composite structure consisting of multiple layers: silicon substrate, silicon carbide buffer layer, and gallium nitride epitaxial layer. Each layer is selected for its specific properties, creating a composite material system that combines the low cost of silicon with the crystal quality benefits of silicon carbide.
2Manufacturing precision
If silicon carbide substrates are used to grow gallium nitride, then crystal quality is improved, but the cost increases significantly
Solution Approach 1:
Instead of using expensive silicon carbide substrates directly, a thin silicon carbide buffer layer is grown on a cheap silicon substrate. This intermediary approach provides the crystal quality benefits of silicon carbide without incurring the high substrate costs.
Solution Approach 2:
The patent uses a disposable silicon substrate as the base, upon which a thin silicon carbide buffer layer is grown. The silicon substrate itself is not reused but provides a cost-effective foundation that enables high-quality gallium nitride growth through the buffer layer.
3Manufacturing precision
If thick gallium nitride epitaxial layers are grown, then the film quality improves, but the growth time and cost increase
Solution Approach 1:
A silicon carbide buffer layer is grown in advance on the silicon substrate before growing the gallium nitride epitaxial layer. This preliminary action prepares the substrate surface with appropriate crystal structure and reduces dislocation density, enabling faster and higher-quality gallium nitride growth.
Solution Approach 2:
The patent optimizes growth parameters including the thickness of the silicon carbide buffer layer (2-10 μm), the orientation of the silicon substrate surface (off-cut angle), and the doping concentration in the buffer layer. These parameter changes enable high-quality film growth in reduced time.
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 ensures good crystallinity of the gallium nitride epitaxial layer and retention of the silicon carbide substrate, thereby achieving cost savings while maintaining high-quality semiconductor substrates for RF components and power devices.
Implementation Method 1
Epitaxy refers to the technology of growing new crystals on a wafer to form a semiconductor layer. Films formed by the epitaxial process have the advantages of high purity and good thickness control
Implementation Method 2
a damaged layer is formed using a laser for separation
Data Source
AI summary
A semiconductor substrate includes a high-resistivity silicon carbide layer and a gallium nitride epitaxial layer. The gallium nitride epitaxial layer is formed on a surface, a thickness of the gallium nitride epitaxial layer is less than 2 μm, and a full width at half maximum (FWHM) of an X-ray diffraction analysis (002) plane is less than 100 arcsec. The thickness of the high-resistivity silicon carbide layer ranges from 20 μm to 50 μm. The surface of the high-resistivity silicon carbide layer has an angle ranging from 0° to +/−8° with respect to a (0001) plane. The micropipe density (MPD) of the high-resistivity silicon carbide layer is less than 0.5 ea/cm2, the basal plane dislocation (BPD) of the high-resistivity silicon carbide layer is less than 10 ea/cm2, and the threading screw dislocation (TSD) of the high-resistivity silicon carbide layer is less than 500 ea/cm2.