Thick-film photolithography based on SU-8 has gained great interest in the field of microreplication technologies. For replication applications the SU-8 structures themselves or electroplated copies of the resist structures are used as casting or embossing tools. In this paper, a simple estimation model is proposed to predict the sidewall profiles of SU-8. This model is based on the effects of Fresnel diffraction and absorption resulting in useful approximations for the pattern profile of SU-8. Its usefulness is successfully verified by experimental results; the estimated and experimental results show similar trends. In addition, by utilizing this model two exposure methods based on reflection and refraction could be developed which avoid negatively sloped sidewall profiles of SU-8. Using these exposure methods, SU-8 preforms without undercut for the replication of optical waveguides have been achieved.

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A hybrid electrical-optical circuit board is demonstrated using polysiloxane as low loss and high-temperature stable waveguide material system. After board lamination at 180°C for two hours and a subsequent temperature treatment at 230°C for 5 minutes the waveguide insertion loss is 0,05 dB/cm at 850 nm wavelength.

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A commercial direct laser writing system operating at 364 nm wavelength is used to expose 90 µm thick layers of SU-8 on silicon. The resist structures are the basis for the fabrication of moulding tools that are used for the replication of multimode optical waveguide components. The influence of the laser power on the shape as well as on the sidewall roughness of the resist structures is studied in detail. The observed profiles are compared to a mathematical model based on the Gaussian beam approximation.

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