Fabricating embedded SU-8 microstructures with asymmetric inside cross section by double-side multiple partial exposure method

Here a double-side multiple partial exposure (DoMPE) method is proposed to fabricate an embedded SU8 microstructure with more flexible inside cross section. The proposed method uses standard lithography equipment and needs only single-layer coating of negative photoresist SU-8 on glass substrate without bonding process. Process parameters, including development thickness at different front and back-side partial exposure doses, are experimentally characterized. Reflection effect due to Cr layer on glass substrate is shown to have influence on the development depth of SU-8 in front partial exposure. It is found that coating thicker SU-8 not only can reduce reflection effect, but also can attenuate cross-link effect due to exposure dose accumulation on SU-8 from both front and back sides. Finally, an embedded SU-8 microstructure is demonstrated to verify that the proposed DoMPE method needs only single-layer SU-8 coating to fabricate not just embedded microstructures, but also embedded microstructure with asymmetric inside cross section. (C) 2014 Elsevier B.V. All rights reserved.