J.A. Woollam M-2000 spectroscopic ellipsometer

Where the M-2000 fits

The J.A. Woollam M-2000 is one of the spectroscopic ellipsometers most often seen in university cleanrooms and thin-film labs, and used units come up regularly as groups move to newer models. It measures film thickness and optical constants (n and k) of single layers and stacks, from a few nanometres of oxide or ALD film to multi-micrometre polymer layers, depending on the material.

What sets the platform apart is speed. The rotating compensator design and CCD spectrometer capture the whole spectrum at once instead of scanning one wavelength at a time. That is why the M-2000 is the usual choice for in-situ monitoring of growth on ALD and sputter chambers, and why a mapping stage can produce a full wafer map in minutes. For routine thickness checks of known films, a reflectometer may be enough; our post on choosing an ellipsometer or a reflectometer sets out the trade-off.

Used M-2000 inspection: what we check

The tool has few moving parts, so inspection focuses on optics, light source and calibration rather than mechanics.

• Lamp and source unit. Lamp type depends on the version. We log lamp hours where the controller records them, check intensity across the spectrum and look for the drop at the blue and UV end that comes with an ageing lamp.
• Compensator and polariser. We run the compensator and check that calibration converges cleanly. Noise or drift here shows up as poor fits on simple oxide samples.
• Detector and spectrometer. We check dark counts and signal level across the range, including the NIR array where fitted.
• Alignment. Source and receiver alignment to the sample, the alignment laser or quad detector, and the stage height adjustment.
• Stage and base. On variable angle bases, we drive through the full angle range. On mapping stages, we check travel, vacuum hold-down and repeatability.
• Reference samples. We measure a thermal oxide on silicon and compare the result with the reference value. The figures go in the inspection report.

Refurbishment scope

A typical refurbishment replaces the lamp, cleans or replaces optical windows, realigns source and receiver, and recalibrates on reference wafers. We check the controller and cabling, replace failed fans and power supplies, and set up a clean PC image with the measurement software. When a unit has been in-situ on a deposition chamber, we inspect the optics for coating and, if needed, replace the windows. Grading follows our four steps (Certified, Refurbished, Inspected, As-is), and a Certified unit includes measured results on reference samples through test and certification.

Upgrades and spare parts

The most requested upgrades are a motorised mapping stage, a variable angle base and focusing optics for small measurement spots. Older systems often run on a PC that can no longer be patched or networked; we move the controller to a supported computer where the software licence allows it. Lamps, windows, sample stages and cabling are the usual spare parts. We source them through the spare parts service and say clearly when a part is new, used or reconditioned.

Facilities

• Single-phase mains power for the controller, lamp supply and PC
• Vibration-stable bench or table; a mapping stage needs more space
• House vacuum or a small pump for the sample chuck on mapping systems
• Viewports with suitable angle and low-strain windows for in-situ use
• Stable room temperature for the best repeatability

Buying advice

Decide on the spectral range first. A V version is the most affordable entry and handles most dielectric and resist films; UV coverage matters for very thin films, wide-bandgap materials and absorbing layers. Then decide between bench-top, mapping and in-situ. Converting an in-situ head to a bench-top base is possible but needs a mounting base and realignment, which affects cost and lead time. Ask for the software version and licence status in writing, because analysis models and material libraries depend on it.

For maintenance after purchase, our calibration service covers periodic checks on reference samples. You can find other thickness and profile tools in metrology and inspection equipment.