Thank you, The imprinter is kind of strange. The lamp is at the bottom. 20 cm above is a vacuum chamber. The bottom of the chamber is quartz 1/2 inches width. I put the mask over the quartz. The Si wafer is upside down so SU-8 is facing the lamp. Two washers are separating the mask with wafer. Do you think that the quartz is scattering the light and the distance between the mask and film is enough to allow it to expose everything? I never thought of this. -----Original Message----- From: mems-talk-bounces+ddimitrov=brooklyn.cuny.edu@memsnet.org on behalf of Andrew Sarangan Sent: Mon 7/7/2014 7:21 PM To: General MEMS discussion Subject: Re: [mems-talk] Unremoved SU-8 after exposure My guess is you are getting exposure due to scattered light from the back side of the wafer (since you are using pyrex). SU8 is very transparent to UV. I use a second wafer on the back side painted with a mat black paint. On Mon, Jul 7, 2014 at 1:25 PM, Dimitar Dimitrovwrote: > > Hello, > > I am graduate student in Brooklyn College and I am trying to reinvent the whole MEMS procedure as I do not have any professional help. My science adviser is from another field. > > I am having difficulties with the developing of SU-8 2025. Here is what I am doing: > > I am spin - coating 4 inch Si or Pyrex wafer to 50 - 60 um thin film > Pre - baking at 96 degrees for 15 min > Sometimes instead I am putting the wafer in the vacuum chamber of my UV imprinter. The vacuum is taking away the solvent and clear most of the bubbles. > UV exposure with a hand made Imprinter: Xenon lamp 22kV at 10 microsec. pulses. Three 30 seconds exposures with couple of seconds pause. > UV lamp creates heat so the wafer is let for 2 - 3 min to relax. > Post bake of 15 min at 95 degrees. > > Developing by tenderly shaking the wafer in a vessel with Propylene glycol monomethyl ether forever. > > The result is that I clearly can see my pattern as exposed SU-8 is yelowish but the unexposed parts are not removed and form thin film with the exposed part. > Less exposure leads to removing all of the polymer. > (This is happening even without any mask but the pattern is formed by metal structure that divides 4 inch wafer into several smaller regions.) > > Can anybody figure out what is my mistake? > > Thank you > Dimitar Dimitrov > _______________________________________________ > 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