Production, research and dummy grade SiC wafers may have the same diameter, polytype and nominal thickness, but they are not interchangeable.

A dummy grade wafer may be suitable for equipment calibration but unreliable for epitaxial growth. A research grade wafer may work well for early material experiments but produce misleading results in device-yield studies. A production grade wafer usually provides tighter defect, surface and geometry control, but it may be unnecessarily expensive for mechanical handling tests.

Choosing the correct SiC wafer grade therefore requires more than comparing prices.

Buyers must consider:

• Intended process
• Epitaxial or non-epitaxial use
• Acceptable crystal defects
• Surface finish
• Wafer geometry
• Electrical uniformity
• Inspection requirements
• Cost of a failed process run

This guide explains the practical differences between production, research and dummy grade SiC wafers and provides an RFQ checklist for selecting the correct material.

SiC Wafer Grade Is Not a Universal Specification

One of the most important purchasing rules is that grade names are not fully standardized between suppliers.

The terms may include:

• Prime grade
• Production grade
• Zero-MPD grade
• Standard production grade
• Research grade
• Test grade
• Dummy grade
• Mechanical grade
• Reclaimed grade

Two suppliers may both offer a “research grade” wafer but apply different limits for micropipes, surface scratches, bow, warp, resistivity uniformity or usable area.

Some suppliers use letter grades such as A, B, C and D, while others classify wafers by defect density or application. XKH, for example, offers SiC substrates identified as production, research and dummy grades across different wafer sizes and conductivity types. 

The grade name should therefore be treated as a starting point. The purchase order must contain measurable acceptance criteria.

Grade Is Separate from Polytype and Conductivity

A wafer grade does not identify its complete material structure.

For example, all the following products may be supplied in different grades:

• 4H-N conductive SiC
• 4H high-purity semi-insulating SiC
• 6H-N SiC
• P-type SiC
• On-axis SiC
• 4° off-axis SiC
• Si-face or C-face polished SiC

A buyer should specify grade together with:

• Polytype
• Conductivity type
• Dopant
• Resistivity
• Orientation
• Off-axis angle
• Wafer face
• Surface finish

A production grade 4H-N wafer for a power MOSFET is fundamentally different from a production grade semi-insulating 4H-SiC substrate intended for GaN RF epitaxy.

What Is a Production Grade SiC Wafer?

Production grade, sometimes called prime grade, is intended for processes where wafer defects and variation directly influence device yield, reliability and manufacturing consistency.

These wafers normally have the tightest available controls for:

• Crystal defects
• Electrical properties
• Wafer geometry
• Surface roughness
• Surface contamination
• Edge quality
• Lot traceability
• Inspection documentation

Typical Applications

Production grade SiC wafers are commonly selected for:

• SiC MOSFET manufacturing
• Schottky barrier diodes
• Junction barrier Schottky diodes
• PiN diodes
• High-voltage power devices
• GaN-on-SiC RF epitaxy
• Automotive qualification
• Aerospace and high-reliability electronics
• Commercial epitaxial wafer production
• Process control and device-yield studies

Important Production Grade Parameters

A production-grade RFQ may include limits for:

• Micropipe density
• Basal-plane dislocation density
• Threading screw dislocation density
• Threading edge dislocation density
• Polytype inclusions
• Carbon inclusions
• Surface scratches
• Edge chips
• Total thickness variation
• Bow and warp
• Resistivity range
• Resistivity uniformity
• Surface roughness
• Usable area
• Particle contamination

Production grade does not automatically mean “zero defects.” If zero micropipes or another specific defect limit is required, it must be stated separately.

Why Defect Control Matters

Defects originating in the substrate can propagate into the epitaxial layer or create new surface defects during growth. Basal-plane dislocations, stacking faults, pits and other extended defects may affect leakage, forward-voltage stability, breakdown behavior and long-term reliability.

A 2025 review in the Journal of Applied Physics explains how multiple SiC epitaxial defects can contribute to device degradation and failure. 

Production grade is therefore usually justified when the cost of epitaxy, device processing and failed dies is much higher than the additional substrate cost.

What Is a Research Grade SiC Wafer?

Research grade SiC wafers provide a balance between functional material quality and purchasing cost.

They may have the correct:

• Polytype
• Diameter
• Conductivity
• Orientation
• Off-axis angle
• Thickness
• Basic polished surface

However, they generally allow more crystal defects, surface imperfections or geometry variation than production grade material.

Typical Applications

Research grade wafers may be appropriate for:

• University research
• Early-stage epitaxial development
• Material characterization
• Process feasibility studies
• Thin-film deposition
• Ion implantation experiments
• Oxidation studies
• Contact-metal development
• Sensor research
• Dicing and polishing trials
• Small-area device prototypes
• Destructive testing

Research Grade Does Not Always Mean Epi-Ready

Some research grade wafers are supplied with an epi-ready CMP surface. Others may contain polishing marks, scratches or subsurface damage that make them unsuitable for high-quality epitaxy.

Before ordering, confirm:

• Si-face surface roughness
• Whether CMP is included
• Scratch limits
• Subsurface damage control
• Cleaning method
• Particle level
• Usable area
• Whether an epitaxial guarantee is provided

A low-cost research wafer with a poorly prepared surface may cause false conclusions during epitaxial development.

When Research Grade Is the Best Value

Research grade is often the most economical choice when:

• Only a small central area will be used
• The wafer will be diced into test coupons
• The experiment does not require production-level yield
• Some surface or crystal defects are acceptable
• The process itself is still under development
• The wafer will be destroyed during testing
• Electrical uniformity across the full wafer is not required

For comparative experiments, all wafers should ideally come from a consistent grade and lot. Mixing different grades can make it difficult to determine whether performance changes come from the experimental process or the substrate.

What Is a Dummy Grade SiC Wafer?

Dummy grade SiC wafers are primarily intended for mechanical, equipment or non-device process testing.

They may have the correct nominal diameter and thickness but relaxed requirements for:

• Crystal defects
• Resistivity
• Polytype uniformity
• Surface scratches
• Edge chips
• Bow and warp
• Surface roughness
• Electrical uniformity
• Usable area

Typical Applications

Dummy grade wafers are commonly used for:

• Equipment installation
• Robot and end-effector calibration
• Wafer cassette testing
• Load-port qualification
• Furnace temperature profiling
• Cleaning-process development
• Coating trials
• Dicing-machine setup
• Laser-processing trials
• Grinding and polishing tests
• Packaging evaluation
• Operator training
• Wafer-handling simulation

What Dummy Grade Should Not Be Used For

Unless the supplier provides additional guarantees, dummy grade should not normally be used for:

• Production epitaxial growth
• Device-yield evaluation
• Electrical reliability testing
• Qualification of critical RF devices
• MOS interface studies
• Benchmarking commercial device performance
• High-value multi-step fabrication

A dummy wafer may survive the handling process but still contain defects that make meaningful electrical evaluation impossible.

Production vs Research vs Dummy Grade Comparison

The exact limits must be confirmed with the supplier because grade terminology can vary.

Defects That Buyers Should Compare Between Grades

Micropipes

Micropipes are hollow-core defects that can severely affect high-voltage devices. Modern production wafers may have very low or zero specified micropipe density.

Research and dummy grades may permit a higher density.

Ask for:

• Maximum micropipe density
• Inspection method
• Edge-exclusion area
• Wafer-level defect map

Basal-Plane Dislocations

BPDs may propagate into the epitaxial layer or contribute to stacking-fault formation in bipolar devices.

Extended defects in SiC epitaxial layers have been linked to reduced device yield and reliability, making BPD limits important for high-value production wafers. Study of SiC defects affecting yield

Threading Screw Dislocations

TSDs can be associated with surface pits, leakage paths and local device failures. Production material normally requires a measurable maximum density.

Polytype Inclusions

A 4H-SiC wafer should maintain the required 4H polytype throughout the usable area. Local 3C or 6H inclusions may affect epitaxy and device performance.

Carbon Inclusions

Carbon-rich inclusions originating during crystal growth may produce surface defects after slicing and polishing or influence epitaxial defect formation.

Scratches and Subsurface Damage

A surface may look mirror-polished while still containing polishing damage below the surface. These defects can become visible after hydrogen etching or epitaxial growth.

For epitaxy, ask whether the wafer is:

• Mechanically polished
• Chemically mechanically polished
• Epi-ready
• Cleanroom cleaned
• Particle inspected

Wafer Geometry

TTV, bow and warp influence:

• Wafer chuck contact
• Robot handling
• Epitaxial temperature uniformity
• Lithography focus
• Film-thickness uniformity
• Wafer breakage risk

Even a dummy wafer requires adequate geometry if it will be used to qualify automated handling equipment.

Dummy Grade Is Not the Same as Reclaimed Grade

A dummy grade wafer may be manufactured as new material but classified with relaxed defect limits.

A reclaimed wafer has already been used and then processed again through steps such as:

• Film stripping
• Grinding
• Polishing
• Cleaning
• Reinspection

Reclaimed wafers may have reduced thickness, altered surface history or unknown contamination risks.

When purchasing low-cost wafers, ask whether the material is:

• New dummy grade
• Reclaimed material
• Recycled process wafer
• Rejected production material
• Mechanical-grade material

These categories should not be assumed to be equivalent.

Which Grade Should Buyers Choose?

Commercial SiC Power Devices

Recommended starting point:

Production grade 4H-N SiC

Specify:

• 4° off-axis direction and tolerance
• Resistivity range
• MPD, BPD, TSD and TED limits
• Epi-ready Si-face CMP
• TTV, bow and warp
• Full inspection documentation

GaN-on-SiC RF Epitaxy

Recommended starting point:

Production grade high-purity semi-insulating 4H-SiC

Specify:

• Minimum resistivity
• On-axis or required offcut
• Surface orientation and polarity
• Defect density
• Surface roughness
• Backside condition
• Full-wafer resistivity uniformity

Early Epitaxial Process Development

Recommended starting point:

Research grade with a guaranteed epi-ready surface

Use production grade reference wafers alongside research grade material when a reliable benchmark is required.

Small-Area Laboratory Experiments

Recommended starting point:

Research grade wafer or diced SiC coupons

Confirm that defects within the test area will not invalidate the experiment.

Equipment and Robot Calibration

Recommended starting point:

Dummy grade

Prioritize:

• Correct diameter
• Correct thickness
• Acceptable bow and warp
• Edge quality
• Mechanical strength

Electrical and crystal-defect specifications may be unnecessary.

Dicing, Grinding or Laser Trials

Recommended starting point:

Dummy or research grade

Choose dummy grade for machine setup and research grade if the experiment must reflect realistic single-crystal behavior or surface quality.

Why the Cheapest Grade Can Become the Most Expensive

A lower wafer price does not always reduce total project cost.

Potential hidden costs include:

• Failed epitaxial runs
• Unusable deposition data
• Reactor time
• Engineering labor
• Incorrect process conclusions
• Device-yield loss
• Requalification
• Broken wafers
• Equipment contamination
• Delayed customer approval

If a dummy wafer causes the loss of a high-value epitaxial run, the substrate saving becomes insignificant.

Buyers should compare total experiment or production cost rather than only the price per wafer.

SiC Wafer Grade RFQ Checklist

Example RFQ: Production Grade SiC Wafer

Application: SiC MOSFET production
Grade: Production grade
Material: 4H-N SiC
Diameter: 150 mm
Orientation: 4° off-axis toward ⟨11-20⟩
Surface: Si-face epi-ready CMP
Resistivity: Defined production range
Defects: MPD, BPD, TSD and TED limits required
Geometry: TTV, bow and warp limits required
Inspection: Full wafer defect and geometry report
Quantity: Qualification lot followed by monthly production

Example RFQ: Research Grade SiC Wafer

Application: CVD epitaxial process development
Grade: Research grade
Material: 4H-N SiC
Diameter: 100 mm
Surface: Si-face epi-ready CMP
Accepted Defects: Relaxed crystal-defect limits
Critical Requirement: No deep scratches in the central test area
Inspection: Basic surface and geometry report
Quantity: 10 pieces

Example RFQ: Dummy Grade SiC Wafer

Application: Wafer-handling robot calibration
Grade: New dummy grade
Diameter: 150 mm
Thickness: Matched to production wafers
Critical Requirements: Diameter, thickness, bow, warp and edge profile
Surface: Standard polish sufficient
Electrical Properties: Not required
Quantity: 25 pieces

Frequently Asked Questions

Can research grade SiC wafers be used for epitaxy?

Yes, provided the wafer has an epi-ready surface and its defect levels are acceptable for the experiment. Production-level yield should not be assumed.

Can dummy grade wafers be used for device fabrication?

Dummy wafers are normally intended for handling, equipment or destructive process tests. Device fabrication is not recommended unless the supplier provides suitable electrical, crystal and surface guarantees.

Is production grade the same as zero-MPD grade?

Not always. Zero-MPD may be a higher or separately defined grade. The purchase order should state the actual micropipe-density limit.

Is research grade suitable for universities?

Yes. It is often the most cost-effective choice for material studies, process development and small-area prototypes.

Should dummy wafers have the same thickness as production wafers?

Yes, when they are used to test robot handling, cassettes, load ports, vacuum chucks or equipment clearance.

Does dummy grade mean reclaimed?

No. Dummy material may be a new wafer with relaxed specifications. Always confirm whether the wafers are new, reclaimed or recycled.

What is the best grade for GaN-on-SiC RF devices?

Production grade high-purity semi-insulating 4H-SiC is normally the safest starting point for qualified RF epitaxy. Research grade may be suitable for early development.

Conclusion

Production, research and dummy grade SiC wafers serve different purposes.

Production grade provides the tightest control of defects, surface condition, geometry and electrical uniformity. It is the appropriate choice for commercial epitaxy, device manufacturing and high-reliability applications.

Research grade offers a practical balance between quality and cost for process development, laboratory testing and prototype fabrication.

Dummy grade is the most economical choice for equipment qualification, robot calibration, dicing trials and other mechanical or sacrificial processes.

The correct purchasing decision should be based on total process risk—not simply the lowest wafer price.

When requesting a quotation, buyers should provide:

• Intended application
• Required wafer grade
• Polytype and conductivity
• Diameter and thickness
• Orientation and offcut
• Surface finish
• Critical defect limits
• Geometry requirements
• Inspection documentation
• Qualification and production quantities

A complete specification allows the supplier to recommend the lowest-cost grade that can still perform reliably in the intended process.