// Showcase

DUV optics alignment and metrology on an enclosed beam path

Four test benches that align optical lithography modules themselves, measure against that alignment, and log every value they used to do it.

Photonics & Laser Semiconductors & Microfabrication

DUV optics alignment and metrology on an enclosed beam path

Photonics & Laser Semiconductors & Microfabrication

01Starting point

Optical modules for lithography systems cannot be signed off by drawing, what counts is what gets measured. Until now it was all done by hand: guide the laser beam across the lab, swap the target, align module and target by feel. That worked fine as long as experienced people were doing it. The problem: alignment and measurement could not be separated. If a value came out bad, nobody could say whether the module was bad or just the setup. And the more modules that needed to go through, the more the human became the bottleneck.

02Approach

We put the reference inside the machine. A laser table serves two measuring stations via a 90 degree swivel, so no beam runs freely through the room any more. The test bench aligns module, target and laser axis itself, measures against that, and logs every value it used to do so. Six measurements run automatically or semi-automatically, manual only where physics genuinely demands it.

03Result

Every measured value can be explained later: aperture, mask position, temperature and the axis that was driven all end up in the log. Even three years from now you can still trace how a value came about. Positioning happens in the micrometre and arcsecond range, verified interferometrically instead of just promised. The operator now only does what genuinely needs manual work. And because the new bench is no bigger than the old one, it fits into the existing cleanroom without any rebuild.

What is inside

Four test benches on a welded substructure with two separately levelled granite plates, manufactured in parallel rather than one after another. Each covers six to seven measurements: wavefront at 0.5 nm sensitivity, focal length accurate to ±0.5 percent, plus boresight, transmission and telecentricity. A five-stage calibration chain brings everything into alignment against the on-site UV laser at the end. Every result comes out in four file formats: human-readable, machine-readable, as raw data and as a report.

What happened next

The four benches are standing, commissioning is under way, factory acceptance is still to come. What already paid off beforehand: we combed through the old measurement logs before a single line of software was written, and found inconsistent values and mismatched labels. They did not matter to a human, but would have become a problem for a machine.

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