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Modeling and Simulation of SU-8 Thick Photoresist Lithography

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Micro Electro Mechanical Systems

Part of the book series: Micro/Nano Technologies ((MNT))

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Abstract

SU-8 photoresist can be used to produce high aspect ratio and three-dimensional (3D) lithographic patterning based on standard contact lithography equipment due to its excellent coating, planarization, and processing properties and thus has become the favorite photoresist material for the fabrication of various microelectromechanical system (MEMS) structures and devices. However, as feature sizes get smaller and pattern complexity increases, particular difficulties arise and need to be carefully considered. The accuracy and precision, with which a feature on a mask can be reproduced throughout a thick resist structure, will depend on key parameters in the setup, the material properties of the SU-8 resist, and the thickness of the resist structure. Modeling and simulation studies may help improve our understanding and process design of the SU-8 lithography, thereby allowing rapid product and process development. In this chapter, the basic process and mechanism of UV lithography of the SU-8 are introduced briefly. Various models for the lithography, including the aerial image model, exposure model, postexposure bake model, and development model, are presented and discussed. Main algorithms for the etching surface advancement simulation, including the string, ray-tracing, cellular automaton, and fast-marching algorithms, are then compared and analyzed. Simulations of the UV lithography of the SU-8 are presented, and a series of experiments have been performed for SU-8 2000 series photoresists under UV source with 365 nm (2.6 mW/cm2) radiation. The simulation results demonstrate to be in agreement with the experimental results. This is useful to optimize the inclined UV lithography processes of SU-8 photoresists and to accurately design and control the dimensions of some MEMS microstructures.

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Authors and Affiliations

  1. Key Laboratory of MEMS of the Ministry of Education, Southeast University, 210096, Nanjing, Jiangsu, China

    Zai-Fa Zhou & Qing-An Huang

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  1. Zai-Fa Zhou
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  2. Qing-An Huang
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  1. Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing, Jiangsu, China

    Qing-An Huang

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Zhou, ZF., Huang, QA. (2018). Modeling and Simulation of SU-8 Thick Photoresist Lithography. In: Huang, QA. (eds) Micro Electro Mechanical Systems. Micro/Nano Technologies. Springer, Singapore. https://doi.org/10.1007/978-981-10-5945-2_3

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