Reinraum

Reinraum

The cleanroom at the Chair for MEMS Materials is class ISO 5, and includes tools for photolitho- graphy and further microstructuring.



In the photolithography section of the cleanroom there is a spincoater which is used to coat the wafers with different photoresists. After a short prebake, the samples can be exposed to UV light by a special laser exposure unit (Heidelberg Instruments) or a mask aligner (Suess, Ma6/Ba6; Fig. right) for patterning. The laser exposure device has a resolution of approximately 5µm. Designs to be written can be easily loaded using a special software which makes it very flexible for rapid writing of unique patterns. This system is also used to produce patterned Cr-masks for the use in the mask aligner.


The mask aligner has a higher resolution (down to 1µm) but it is not as flexible since Cr-masks are needed for the exposure. Higher throughput of samples can be achieved with the mask aligner since the whole wafer is exposed at once, and not in a serial way as with the laser exposure unit.

The exposed samples are developed and then used for lift-off processes or etching steps. For the etching of Si a special KOH-etching bath is used where the KOH is heated to a constant temperature (80°C) for higher and stable etching rates.

MEMS structures are being produced by a multitude of repeated processing steps like deposition of thin films, etching and photolithography. Examples would be microcantilevers or microhotplates.

For the characterization of film thicknesses or the measurement of etching rates, a profilometer (Ambios, XP2; Fig. left) is used which is also situated inside the cleanroom.