The best way is to measure the underetch after the mask-strip. If you measure the line-width before etching and after mask-strip, then your underetch is half of the difference between the two values. With a resist-mask you can also often see the underetch after etching as a somewhat different coloured edge at the border of the mask-pattern. You might need a intefference-microscope for this though. With a metal etch-mask this will not work, since the metal is not transperant (at least, not for the metal-thicknesses that are normally used as etch-mask). You could try and see if you can see/measure the underetch from the back-side of the wafer though, since your using glass substrates. So if you place the wafer with the backside up, you could the look through the glass and focus on the front-side. Never tried it myself, but it might be something worth trying. If you try this, just be carefull when focussing and keep track of the disctance of the objective to the substrate, since you could end up damaging your sample. Succes, Jason ___________________________________________________________ Jason Viotty Senior Process Engineer C2V http://www.c2v.nl -----Original Message----- From: Tom Fan [mailto:Tom.Fan@asu.edu] Sent: donderdag 4 september 2003 2:49 To: mems-talk@memsnet.org Subject: [mems-talk] Underetch Measurement Hi All, I am wondering how people measure the magnitude of underetch when doing an isotropic wet etch of glass substrates (whether using PR or metals as etch masks)? Is it by using the SEM? Thanks, Tom Fan _______________________________________________ MEMS-talk@memsnet.org mailing list: to unsubscribe or change your list options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk Hosted by the MEMS Exchange, providers of MEMS processing services. Visit us at http://www.memsnet.org/