Hello Bill, what I usually do is to wipe the keys with the acetone. As the first layer is already after PEB and cross-linked it withstands the solvent quite well, the second layer is easy to dissolve. I use at least two swabs for one key, first removing the SU8 in wider area around the key and second to remove residues from inner part. Of course this can be done only if keys are far enough from the product, or you have to sacrifice some products close by. Common way to avoid this issue completely is to use the substrate which already contains the alignment keys (e.g. in metal) and align both SU8 layers to it. With best regards, Daniel Daniel Figura smartfabgroupT Company process consulting . data processing . fab software Phone: +421 944 45 26 86 E-mail: daniel.figura@smartfabgroup.com, Web: www.smartfabgroup.com Disclaimer notice: The information contained in this message and any attachments is intended only for the personal and confidential use of the designated recipient(s) named above. If you are not the intended recipient of this message you are hereby notified that any review, disseminitation, distribution or copying of this message is strictly prohibited. If you have received this message by error, please notify the sender immediately. -----Original Message----- From: mems-talk-bounces+daniel.figura=smartfabgroup.com@memsnet.org [mailto:mems-talk-bounces+daniel.figura=smartfabgroup.com@memsnet.org] On Behalf Of yutchow2@gapps.cityu.edu.hk Sent: Thursday, May 15, 2014 15:32 To: gjenkins971@gmail.com; mems-talk@memsnet.org Subject: [mems-talk] ??: Alignment problem with Multilayer SU-8 fabrication Thanks for your suggestion. Unfortunately, I don't have phase contrast microscope. In addition, the first layer structure was not clear to see and difficult to observe both the alignment mark on the first layer and on the mask clearly at the same time. Are there any usual practice to locate and align the second layer with high accuracy? I am using Karl Suss MA6. Thanks. Regards, Bill ------ ????------ ???: Gareth Jenkins ??: ??, 2014?5?15? 8:30 ???: General MEMS discussion; ??:Re: [mems-talk] Alignment problem with Multilayer SU-8 fabrication I used to use a phase contrast microscope to align layers. Once I found the alignment marks under the microscope, I would manually scratch the resist with a scalpel (which needs a steady hand). Then I could align the second layer to the scratches on the mask aligner. On 14 May 2014 17:14, Bill Chow wrote: > Dear all, > > Recently, I am working on a two layer SU-8 structure. All the process are > followed with the suggested procedures. However, the problem appeared when > I try to look for the alignment mark, after I have spin coated and prebaked > the second layer of SU-8, it is difficult to locate the first layer exposed > features. > > First layer thickness : 3.7um > Second layer thickness : 17 - 20um > > I found that it is extremely difficult to locate the first layer pattern > under the microscope after I have coated the second layer, despite it can > be seen be naked eye.... Sometimes if there are some defect or bump in the > 2nd layer above the alignment mark, then it can be seen clearly. However, > it is a random process and will affect my pattern. Are there any ways to > improve the visiblity of the alignment mark after I have coated the 2nd > layer? Thanks. > > Regards, > > Bill > > _______________________________________________ > 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 _______________________________________________ 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