SU-8 is a negative tone proxy type resist which allows high aspect ratio for micro machining. SU-8 molds can be used for micro casting and embossing for making high aspect MEMS. A quick way to produce prototypes (Design -> Expose -> Prototype) is presently an important task in the micro fabrication. In this work we demonstrate the ability of multiple layer and binary structuring of SU-8 using maskless photolithography by the DWL66 device. As light source, we used a 30 mW He-Cd-Laser at 325 nm wavelength. The intensity is varied over 31 steps (grey levels) by an acousto-optical modulator (AOM) which provides the desired grey tone levels. By means of microlens arrays (MLA) we represent the achieved results by back side exposures. It can be shown that in addition to producing the curvature of the lenses by intensity modulation, the total height of lenses can be controlled by using supplementary attenuation. The total achieved height of micro lenses is approximately 65 μm resulting from a 100 μm thick SU-8 25 resist made by multiple coating method. Good chemical, mechanical and optical properties make SU-8 interesting for different applications as micro devices in micro-optics and micro-optoelectronics.
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