Hello Aaron, we often observed the "crater landscape" or "orange skin" while KOH and especially TMAH etching. Following measures improved the surface quality (high purity chemicals implied): annealing of potential crystal defects before etching and scrupulous acid cleaning of all etching equipment. The influence of light on the etching (depending on type and amount of dopants) should be considered also. Regards, André -----Ursprüngliche Nachricht----- Von: mems-talk-bounces+aboedecker=imsas.uni-bremen.de@memsnet.org [mailto:mems-talk-bounces+aboedecker=imsas.uni-bremen.de@memsnet.org] Im Auftrag von Aaron Glatzer Gesendet: Mittwoch, 2. Juli 2014 19:42 An: mems-talk@memsnet.org Betreff: [mems-talk] KOH etch surface "craters" We are etching some 300 micron deep trenches using KOH, and we are occasionally getting "craters" in the trench bottom surface. These are 2-4 micron deep 50-75 micron wide spots on the bottom of the trench. Is this typical for KOH etch? Has anyone else seen this kind of thing? Any idea what causes it? Technical details: <100> silicon. Masked with 2kA low stress LPCVD nitride. Nitride etched with SF6 plasma RIE; we guesstimate we etch 2000A into the Si (based on known-etchrate, and observed overetch time on endpoint signal). Resist stripped in O2-ash/piranha/O2-ash sequence. KOH 45%, etched at 85C, for about 5.5 hours. Typically we get a mildly textured surface (per optical inspection), but as indicated above occasionally we get what look in microscope like blisters, but optical profilometer indicates is actually a "crater". Any insight into this is appreciated. thank you, Aaron G. -- Aaron Glatzer phone (419) 241-6963 x13 Lead Process Engineer fax (419) 241-6966 Midwest Microdevices, LLC aglatzer@midwestmicrodevices.com 329 14th Street Toledo, OH 43604 --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _______________________________________________ Hosted by the MEMS and Nanotechnology Exchange, the country's leading provider of MEMS and Nanotechnology design and fabrication services. Visit us at http://www.mems-exchange.org Want to advertise to this community? See http://www.memsnet.org To unsubscribe: http://mail.mems-exchange.org/mailman/listinfo/mems-talk _______________________________________________ Hosted by the MEMS and Nanotechnology Exchange, the country's leading provider of MEMS and Nanotechnology design and fabrication services. Visit us at http://www.mems-exchange.org Want to advertise to this community? See http://www.memsnet.org To unsubscribe: http://mail.mems-exchange.org/mailman/listinfo/mems-talk