Silicon carbide (SiC) substrates are available in multiple quality grades tailored to different stages of device development and manufacturing. The three most common classifications—Dummy Grade, Research Grade, and Production Grade—represent distinct levels of material quality, defect density, and process suitability. Understanding these differences is essential for selecting the appropriate substrate for specific applications.

1. Dummy Grade SiC

Definition: Dummy grade SiC substrates are cost-effective, low-quality wafers used primarily for equipment calibration, process testing, and operator training, rather than for high-performance device fabrication.

Characteristics:

High defect density: Threading dislocations and micropipes are abundant.
Lower surface quality: Polishing precision is limited, resulting in higher surface roughness.
Poor electrical uniformity: Resistivity and conductivity may vary significantly across the wafer.

Applications:

Epitaxy process development and pre-run calibration
Cutting, grinding, or polishing tool qualification
Cleaning, etching, and test structure evaluation

2. Research Grade SiC

Definition: Research grade SiC substrates provide intermediate to high quality suitable for laboratory research, prototype development, and small-scale process validation.

Characteristics:

Moderate defect density: Significantly lower than dummy grade, but not at production standards.
Improved surface finish: Chemical-mechanical polishing (CMP) reduces surface roughness to ~0.5 nm.
Stable electrical properties: Available as conductive or semi-insulating with reasonable uniformity.

Applications:

Device concept studies (MOSFETs, JFETs, HEMTs, etc.)
Process optimization and parameter development
Material defect analysis and mechanism research

3. Production Grade SiC

Definition: Production grade SiC substrates meet stringent industrial standards for high-volume device fabrication. These wafers are supplied by leading global manufacturers and are used in commercial-scale power and RF electronics.

Characteristics:

Ultra-low defect density: Threading dislocation density typically <1,000 cm⁻².
High-precision CMP: Atomically flat surfaces free of visible scratches.
Excellent electrical uniformity: Consistent resistivity for both conductive and semi-insulating types.
Reliable volume supply: Qualified for industrial yield requirements.

Applications:

Mass production of SiC MOSFETs, Schottky barrier diodes (SBDs)
GaN-on-SiC RF and microwave devices
Advanced sensors and quantum devices

Summary Table

Grade	Defect Density	Surface Quality	Electrical Uniformity	Primary Applications
Dummy Grade	High (>10⁴ cm⁻²)	Basic	Poor	Process calibration, equipment tuning
Research Grade	Medium (10³–10⁴ cm⁻²)	Good	Moderate	R&D, prototype, defect studies
Production Grade	Low (<10³ cm⁻²)	Excellent	High	Mass production of devices

 

Conclusion

Selecting the correct SiC substrate grade is critical for efficient device development and manufacturing. Dummy grade wafers reduce costs in early-stage process trials, research grade wafers enable scientific exploration and technology validation, while production grade wafers ensure high yield and device reliability at an industrial scale. This structured approach optimizes R&D efficiency and accelerates the commercialization of high-performance SiC-based power and RF electronics.