Abstract

A simple and controllable method is proposed to fabricate suspended three-dimensional carbon microelectromechanical systems (C-MEMS) structures by tailoring diffraction-induced light distribution in photolithography process. An optical model is set up and the corresponding affecting parameters are analyzed to interpret and predict the formation of suspended structures based on Fresnel diffraction theory. It is identified that mask pattern dimensions, gap distance between the photomask and photoresist, and the exposure time are critical to the final suspended structures, which have also been verified through experimental demonstrations. The fabricated biocompatible suspended C-MEMS structures could find wide applications in electrochemical and biological areas.

Highlights

  • Three-dimensional (3D) C-MEMS structures consisting of high aspect-ratio carbon microelectrodes have drawn much attention due to their good mechanical, electrical, electrochemical properties and excellent biocompatibility [1,2,3]

  • Their study results show that the SU-8 becoming more absorbing as the exposure time increases, which means that small light energy E brought by diffraction effects will be absorbed only by the surface layer of the SU-8 even if overexposure were applied to the SU-8 photoresist

  • The samples are characterized by Scanning Electron Microscope (SEM), and the results are presented in the following

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Summary

Introduction

Three-dimensional (3D) C-MEMS structures consisting of high aspect-ratio carbon microelectrodes have drawn much attention due to their good mechanical, electrical, electrochemical properties and excellent biocompatibility [1,2,3]. These microelectrodes derived from thick photoresist can be used for various miniaturized carbon-based devices such as micro-batteries, super-capacitors and biosensors [4,5,6]. The fabrication process of C-MEMS structures with high aspect-ratio mainly includes two steps, lithography and pyrolysis process, where thick photoresist micropatterns created in lithography process are transformed into amorphous glassylike carbon microstructures under high temperature and inert atmosphere. A controllable methodology will be proposed for the fabrication of suspended C-MEMS structures

The optical model in UV lithography
The energy threshold model
Light intensity distribution simulation
Experimental details
Results and discussion
Conclusion
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