Carson, You have to remember that SU-8 is a negative tone material - basically, where you expose, the material will remain. As such, this means that, the higher your exposure gets, the wider your remaining linewidths will become. In the case of a massive overexposure (such as your 100second, or 2 J/cm2), this can actually prevent narrow trench features from developing out. An optimal dose for the thickness you are exposing is ~300 mJ/cm2 (or, about 15 seconds). Unfortunately, the nature of the SU-8 will mean that some residual stress will exist in the film, but with care taken during the baking steps, this stress can be minimized. One final comment (one I have made before) - be very careful that you are not allowing the SU-8 to experience UV wavelengths below 350nm - this can cause extremely unpredictable results during 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: Wednesday, December 08, 2004 9:02 AM To: MEMS-talk@memsnet.org Subject: [mems-talk] SU8 exposure time Hello All, I am trying to find the best exposure time for a SU8-2035 with a thickness of around 50 um This is not looking to be very easy. I am working with a UV i-line 365 nm, with 20 mW/cm2 For high exposure time (up to 100s ), I see that my structure does not developp at all, i.e. the exposed polymer is not removed in the developper although the sutructre is clearly visible with a color difference between the exposed and non exposed part For reasonnable exposure time (20 s), I have a good developpment but I have always a resulting mould that is small as my mask. i.e some feature of my pattern of 200 um would lead to only 100 um cavity in my developped polymer and so one. Finally, when I go down to 7 seconds, I have a good resulting mould, with much better dimensions, but I have enormous stress on my polymer and sometimes delamination which makes me thing I am under exposing of course Could someone share his own experience about that? especially about the over-exposure'? Many thanks Carson --------------------------------- Découvrez le nouveau Yahoo! Mail : 250 Mo d'espace de stockage pour vos mails ! Créez votre Yahoo! Mail Avec Yahoo! faites un don et soutenez le Téléthon ! _______________________________________________ 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/