Low Cost Optical Maskless Photolithography Patterning for Pt/Ti Micro-Electrodes for Microelectromechanical Systems Using a Microlight 3D System

The research described in this article focused on developing a process to produce microelectrodes $20 \mu \mathrm{~m}$ long/ $10 \mu \mathrm{~m}$ wide ($\lt {5 0} \mu \mathrm{m}$ sideway dimension, which is the current limit for metal structures produced by lift-off patterning using a microlight 3D system), using maskless photolithography equipment (SmartPrint UV Microlight 3D) for exposing a thin layer of nlof 2020 negative photoresist sensitive to i-line. The sacrificial nlof 2020 layer used is $\sim 2 \mu \mathrm{~m}$ thick, estimated from the provider technical data sheet. First, a rectangular cantilever was patterned on the substrate. The patterning process revealed that increasing the intensity of the UV light enables to increase the resolution to produce smaller structures on the photoresist layer, which is not regularly done by contact mask photolithography. UV light exposure time, and prebaking and post-baking time were also varied to optimize the definition of the electrode structures. Finally, the process was integrated on top of an ultrananocrystalline diamond (UNCD)-based microcantilever for testing the process as second step in the development of UNCD-based microcantilevers.