Michael, It is entirely a resolution problem. Due to the high reactivity at lower wavelengths, a large degree of T-topping can occur, in some cases, causing trench features to completely seal over at the top, while remaining open underneath (think of the way a canopy merges together in a rainforest, while leaving a large amount of space between the trunks...). 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 Michael L Sent: Saturday, December 11, 2004 4:55 AM To: mems-talk@memsnet.org Subject: [mems-talk] SU8 exposure time Chad, Could you provide more elaboration on the nature of unpredictability in results when exposing at UV wavelengths below 350nm. Is this primarily a resolution problem, or will the mechanical properties of the film also be affected? Thanks, Michael >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 _______________________________________________ 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/