Guides / Materials

Machining Super Invar and Invar 36 for Semiconductor Equipment

September 20, 2026

Semiconductor fabrication and metrology equipment operates at a precision level where a few microns of drift is already a defect. Wafer stages, reference frames and gauge fixtures are places where a fraction of a degree of temperature variation, multiplied across a structure, can shift a measurement or an alignment enough to matter, which is why Invar and Super Invar show up regularly in this equipment even though cleanrooms already control temperature tightly.

Why low expansion matters even in a controlled environment

A modern cleanroom holds temperature to a tight band, often within a fraction of a degree, but a fraction of a degree is not zero. Over a structure a few hundred millimeters across, even a small, real temperature fluctuation causes measurable expansion in aluminum or steel, on the order of microns. In equipment where the tolerance budget is itself only a few microns, that expansion consumes a meaningful share of the available margin before any other error source is accounted for.

Invar 36, with a typical CTE around 1.2 to 1.6 ppm per degree C versus aluminum’s roughly 23.6, reduces that source of error at the material level. Super Invar, with a typical CTE around 0.3 to 0.6 ppm per degree C, goes further for the tightest applications, though it holds that low expansion over a narrower temperature band and costs more, a tradeoff also covered in Invar for optical benches and telescope structures.

Where it shows up in semiconductor and metrology equipment

• Wafer stage components, where the structure holding and positioning the wafer has to maintain its geometry through the process cycle.
• Reference frames and metrology fixtures, the structural elements that other measurements are made relative to, where any drift in the reference itself corrupts every measurement taken against it.
• Gauge blocks and calibration fixtures, where dimensional stability is the entire point of the part.
• Mask and reticle handling fixtures, where positional accuracy directly affects pattern alignment.

What this means for machining and inspection

Semiconductor and metrology equipment tends to combine three requirements that are each individually demanding, and together push toward shops with genuine Invar experience rather than general machine shops that occasionally cut it:

Tight tolerance on functional features. Reference plates and stage components often carry tolerances at the tighter end of what is achievable, discussed in more detail in Invar machining tolerances, which typically requires the full rough, stress relieve, finish and stabilize sequence rather than a shortened process.

Cleanliness and contamination control. Parts destined for cleanroom use often need controlled cleaning processes and packaging specifically to avoid introducing particulates or residues into the semiconductor process. This is separate from and in addition to the dimensional requirements, and it needs to be specified explicitly, since a shop’s standard packaging for a general industrial part is not cleanroom compatible by default.

Documentation and traceability. Metrology and reference equipment often needs a documented chain of inspection data, tying the finished part’s measured dimensions back to a specific process and material lot, similar in spirit to the traceability requirements covered in Invar material certification.

Fixture and reference plate design considerations

A few design level choices affect how well an Invar reference structure performs in service:

• Symmetric geometry reduces asymmetric thermal response, even though Invar’s overall expansion is already low
• Mounting points should isolate the precision structure from thermal or mechanical influence from the surrounding equipment frame, which is often a different, higher expansion material
• Surface finish on reference and mounting faces affects both optical or capacitive measurement accuracy and mechanical repeatability, covered in surface finish and coating options for machined Invar

Specifying a semiconductor or metrology Invar part

Useful details to include on the drawing or RFQ:

• The operating temperature stability of the environment the part will sit in, even if it is a controlled cleanroom
• Critical tolerance and flatness requirements, called out as GD&T on the specific features that matter
• Cleanroom compatibility requirements for cleaning and packaging
• Documentation and traceability requirements for your program

Getting a quote

This category of part usually benefits from a shop that has handled precision reference or metrology hardware before, not just Invar in general, since the combination of tight tolerance, cleanliness and documentation is more specific than a typical Invar bracket or mount.

Send your drawing through our RFQ form with your precision and cleanliness requirements noted, and we match you with shops suited to that combination.

Frequently asked questions

Keep reading

• Machining Invar Layup Molds and Mandrels for Composite Parts
• Machining Invar for Cryogenic and Vacuum Applications