Investigation of SU8 as a structural material for fabricating passive millimeter-wave and terahertz components

Abstract

This paper is to provide a systematical review of the technical issues of SU8 fabrication for millimeter-wave and terahertz components based on research works carried out at the University of Birmingham in the past decade. A design-for-manufacturability (DFM) approach is followed. The flexibility of the SU8 process enables many novel device structures. Challenges and problems during the fabrication will be discussed and demonstrated with examples. The measurement of the devices is also a significant challenge when the critical dimensions of the device shrink and special testing fixtures are needed in some cases. Finally, a brief overview of the issues discussed above is given for future guidance.

Submillimeter‐wave waveguide filters fabricated by SU‐8 process and laser micromachining

“…SU-8 micromachining is a photolithographic-based process and is another feasible solution to fabricate millimetre-wave and terahertz waveguide components. SU-8 is capable of constructing threedimensional terahertz waveguide structures with high aspect ratios (greater than 20 : 1), high-dimensional accuracy (tolerance within a few microns), and excellent surface integrity (roughness on the order of tens of nanometres) [24]. The SU-8 process has been utilised to demonstrate a range of millimetre wave and terahertz circuits, including filters [21,[25][26][27][28], waveguides [29,30], Butler matrix with a patch antenna array [31], an orthomode transducer [32], and antennas [33][34][35].…”

“…Finally, several layers of metal-coated SU-8 are assembled together using precision alignment pins. More detailed discussion about the fabrication process can be found in [21,24].…”

Thin-film conformal fluorescent SU8-phenylenediamine

“…2,3 After revealing numerous advantages of SU8, it became a technological platform across many disciplines, including microfluidics, 4–7 micromechanics, 8 biomedicine, 9 optoelectronics, 10,11 and many others. 12–15…”

Dry Film Photoresist-Based Microfabrication: A New Method to Fabricate Millimeter-Wave Waveguide Components

“…Micromachining due to the high dimensional accuracy and the possibility of achieving high-aspect-ratio structures has the potential for the manufacturing of mm-wave components. Among different micromachining techniques, silicon-based micromachining [ 5 , 6 ], SU8 photoresist-based process [ 7 , 8 , 9 , 10 , 11 ], and LIGA-based thick layer electroplating [ 12 , 13 ] are suitable for manufacturing mm-wave components.…”