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Choose prime or test grade silicon wafers based on your process stage, not marketing labels. We stock and source multiple grades across common diameters.
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Wafer Grade Is a Decision Tool, Not a Badge
Prime and test grade silicon wafers start from the same base material. The difference is not purity, chemistry, or dopant species it is how tightly mechanical and surface specifications are controlled. Choosing the right grade is about matching wafer capability to process risk.
The First Question You Should Ask
Before looking at prices, ask one thing: “Will this wafer produce real devices or just validate a process step?”
What You Gain With Prime Grade Wafers
Prime grade silicon wafers are controlled for flatness, site flatness, TTV, particle counts, and cosmetic quality. On large diameters, this can mean TTV controlled to around 2 µm and site flatness tight enough for advanced lithography.
This level of control matters when depth of focus, overlay accuracy, and defect density directly affect device yield.
What Test Grade Gives Up (and Why Labs Still Use It)
Test grade wafers allow more polish marks, surface haze, and thickness variation. For example, 200 mm test wafers may allow TTV values up to 25 µm.
That sounds large but for many steps like oxidation, diffusion, film deposition, etch benchmarking, or furnace uniformity mapping, those differences do not invalidate the data.
The Budget Impact Is Not Subtle
At the same diameter, prime grade wafers can cost more than ten times as much as test grade. A typical example in US catalogs shows:
- 100mm prime grade: ~$315 per wafer
- 100mm test grade: ~$19.90 per wafer
For a development program using dozens of wafers per iteration, grade selection alone can determine whether a project stays funded.
How US Labs Actually Use Prime and Test Together
Most successful R&D teams do not choose one grade permanently. Instead, they switch grades as the process matures:
- Early exploration: Test grade to tune recipes and equipment
- Process tightening: Test grade with added metrology
- Final verification: Prime grade for device-quality confirmation
- Transfer or publication: Prime grade only where required
Why Diameter Changes the Prime vs Test Decision
At small diameters (25.4mm, 3-inch), handling and fixtures often dominate performance, making grade differences less critical. At 100mm and above, flatness and TTV increasingly affect lithography and yield, which is why prime grade becomes more important as diameter increases.
Why Grade Choice Also Affects Supply Risk
Large-diameter prime wafers are more sensitive to tariffs, capacity constraints, and lead-time fluctuations. Using test grade for non-critical runs reduces exposure while preserving access to prime wafers when they truly matter.
Prime grade is not “better” in every situation , it is simply more controlled. Test grade is not a compromise, it is a deliberate cost and risk optimization tool. The most effective US wafer strategies use both, switching grades as technical risk decreases and device stakes increase.