Lamp house, stage, alignment optics and mask holder sizes decide what an older aligner can still do. A checklist for your inspection visit.
A used mask aligner is often the first serious tool a new cleanroom buys, and the one students will use most.
Platforms such as the SUSS MicroTec MA6 and MJB4 or the EV Group EVG620 were built in large numbers and many are still running decades later. That is good news for buyers, but it also means the market holds everything from carefully maintained tools to aligners that sat unpowered in a corridor for five years. This checklist covers what to look at before you commit, whether you inspect the tool yourself or ask for a report.
Before you look at any listing, write down four things: the largest wafer or substrate you will expose, the mask size you already own or plan to buy, the smallest feature you need to print, and whether you need backside alignment. These answers narrow the field quickly.
A manual aligner for 100 mm (4 in) wafers and 127 mm (5 in) masks is a different purchase from a semi-automatic tool for 150 mm (6 in) wafers with 178 mm (7 in) masks. Backside alignment is an option on several platforms, but it needs its own microscope optics and is rarely retrofitted cheaply. If your group works with pieces rather than full wafers, check that suitable chucks exist for the model, because small-sample work is where many older configurations fall short.
Resolution claims in listings are usually the manufacturer's best case under vacuum contact with thin resist. For proximity exposure, the gap and the wavelength set the limit, so treat headline numbers as a ceiling rather than a promise.
Most older aligners use a mercury short-arc lamp, commonly in the 350–1,000 W range depending on the model and exposure field. The lamp itself is a consumable. What matters more is the condition of everything around it.
During a visit, ask for an intensity and uniformity measurement across the exposure field. A uniformity figure measured on the day tells you far more than a datasheet.
If you want to stop buying mercury lamps altogether, a UV-LED source can replace the lamp house on many common platforms. Our UV-LED conversion page explains what changes for your exposure recipes.
The mechanical side of an aligner wears more slowly than the optics, but when it goes wrong it is harder to fix.
Move the stage through its full X, Y and theta travel. It should feel smooth, with no dead spots or backlash. Ask the seller to run a wedge error compensation cycle with a wafer loaded. This step levels the wafer against the mask before exposure, and a sticky or uneven WEC mechanism shows up as poor contact and variable linewidth across the wafer.
Then check the alignment microscope:
Finally, run a contact test. Soft, hard and vacuum contact should each engage cleanly, and the vacuum seals around the chuck should hold. Cracked or flattened seals are cheap to replace but tell you how the tool was treated.
Mask holders and wafer chucks are where many used purchases go wrong. A tool may be listed as "150 mm capable" while only a 100 mm chuck and a 127 mm (5 in) mask holder are in the crate.
Make a list of every holder and chuck that comes with the tool and match it against your wafer and mask sizes. Ask about transparent chucks for backside alignment, piece holders, and any spacers needed for proximity exposure. Replacement holders for well-known platforms can usually be sourced, but lead time varies and some older parts are only available second-hand. Our spare parts service can check availability before you buy.
Older aligners range from fully manual with mechanical timers to semi-automatic tools with a PC or embedded controller. Check that the controller boots, that recipes can be saved and loaded, and that the exposure timer agrees with a stopwatch.
Ask for manuals, electrical drawings and any service logs. Missing documentation does not rule out a tool, but it adds time to every repair. Note the controller hardware too: some older PCs and interface cards are hard to replace, which is where a control-system retrofit becomes worth discussing.
A few signs deserve a second look: a lamp house with heavy discolouration around the vents, an exposure shutter that sticks or sounds uneven, a stage that has been locked with tape for transport and never released, or a seller who cannot power the tool up at all. None of these is a reason to walk away on its own, but each should be priced into the refurbishment scope before you agree a deal.
Mask aligners are among the easier tools to install, but they still need planning. Typical requirements, depending on configuration:
Check the footprint and the height of the lamp house against your door openings and ceiling, and allow space behind the tool for lamp changes.
When you compare offers, compare like with like. A tool sold As-is, with photos and its known service history, is a different proposition from an Inspected one that has been powered up and checked against its original specification. Our how we inspect page sets out what each condition grade means and what the report contains.
At a minimum, ask for intensity and uniformity data, a record of stage and contact checks, the lamp hours, the list of holders and chucks, and photos of the optics. If the tool will be refurbished before delivery, ask which parts will be replaced and how the result will be verified.
We inspect and refurbish common aligners including the SUSS MA6 and the EVG620, recalibrate intensity and uniformity, and convert mercury lamp houses to UV-LED. If you are comparing used aligners, send us the listing or the tool's history and we will tell you what we would check first. For ongoing work after installation, see our calibration service.
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Tell us the process, wafer size and facilities. We shortlist tools that fit and send an inspection report with every offer.