Laetita, You mention that you have considerable swelling of your polymer after exposure. At what point after exposure? After the post-exposure bake? Or after the develop? 100% swelling is very unusual. It may be that you performed an insufficient curing step (either on soft bake, or during the post exposure bake) that allowed absorption of developer solvent into the exposed region. It may also indicate an insufficient exposure, such that the cross-link process is incomplete, again leading to absorption of the solvent. The lift-off that you are observing is making me lean towards under-exposure as an issue. My reasoning is as follows: 1) If the issue is under exposure, the upper layers of the resist will have received the greatest dose (since it absorbs some of the energy that would otherwise penetrate), promoting cross-link in the upper portions. However, the lower regions would still be under dose, so that cross-linking does not complete (or may barely occur at all). During develop, these areas will be attacked and dissolved by the developer. 2) If, instead, the issue were an insufficient post exposure bake, assuming you are using a contact hot-plate, the greatest amount of heating (and cross- linking) would occur close to the wafer surface. Then, you would see a height loss in your features, but no lift-off. Of course, the possibility also remains that you are performing an insufficient processing in all categories (bake, exposure). Some tips: - If you are using the process parameters from the data sheets on MicroChem's website (at www.microchem.com), make sure that your bakes are performed on a hotplate. - The exposure dose information is for intensities measured at I-line (365 nm). SU-8 is only sensitive to radiation with wavelengths below 400nm (thus, it is transparent to g-line - 435nm - and h-line - 405nm). In addition, it is highly sensitive (to a prohibitive degree) to radiation below 350nm. So, best results are achieved either by exposing only at 365nm, or, exposing with a broadband source that includes I-line (360 - 450, for instance). However, it is very critical that you base your dose on an intensity measured at I-line, since the corresponding intensities at the other bands will be different (although proportional), and will lead to an incorrect exposure. Best Regards, Chad Brubaker EV Group invent * innovate * implement Technology - Tel: 480.727.9635, Fax: 480.727.9700 e-mail: c.brubaker@EVGroup.com, www.EVGroup.com This message and any attachments contain confidential or privileged information, which is intended for the named addressee(s) only. If you have received it in error, please notify the sender immediately and then delete this e-mail. Please note that unauthorized review, copying, disclosing, distributing or otherwise making use of the information is strictly prohibited. -----Original Message----- From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org] On Behalf Of laetitia philippe Sent: Thursday, December 02, 2004 7:40 AM To: mems-talk@memsnet.org Subject: [mems-talk] SU8-developpement problems Hello All, I am using the SU-8 2035 for making film thicknesses of 50 microns. I am proceeding with the soft and hard bake in a normal way. After my exposure I can see clearly that around the structure I have considerable swelling of my polymer, around 100% of my original thickness. SOmetimes the polymer sticks well, sometimes it delaminates from its region Also, the structure I expose is somewhat always minored in dimensions in comparison of my original mask. Has someone ever encountered this problem? Is it due to a wrong exposure time (I am using a UV source , 365 nm), 7 to 9 seconds? Is it due to a bad curing? maybe should be longer to reduce --------------------------------- Créez gratuitement votre Yahoo! Mail avec 100 Mo de stockage ! Créez votre Yahoo! Mail Le nouveau Yahoo! Messenger est arrivé ! Découvrez toutes les nouveautés pour dialoguer instantanément avec vos amis.Téléchargez GRATUITEMENT ici ! _______________________________________________ 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/