Authors: O. Mertsch, A.D. Walter, B. Loechel and D. Schondelmaier
Affilation: BESSY GmbH, Germany
Pages: 332 - 335
Keywords: lithography, plant-like structures, ultra-hydrophobic, contact angle, SAM
A novel method for fabricating ultra-hydrophobic surfaces for bio chip and MEMS applications is presented. The base of this method is a lithographic process with some substantial changes of the exposure conditions. Plant-like structures are being generated by means of a backside exposure of a negative photo resist through an UV-permeable substrate. A standard silica glass mask with periodical elements of specific structure widths in the micrometer range is used. We take glass of a certain thickness as substrate which additionally serves as a several hundred micrometer thick proximity gap between resist and mask. Caused by this large gap, the light has a long propagation way and generates an interference pattern when reaching the resist. Such exposure conditions result in tapered structures with porous side walls which even interconnect on the ground depending on the gap width and the distance between the structures on the mask. For very small gaps between the exposed structures, the resist alone generate very high contact angels of more than 120° for water. With an additionally coating procedure of self assembled monolayer the contact angle can be increased above 160°.