UV-LIGA microfabrication of 220 GHz sheet beam amplifier gratings with SU-8 photoresists

Microfabrication techniques have been developed using ultraviolet photolithography (UV-LIGA) with SU-8 photoresists to create advanced sheet beam amplifier circuits for the next generation of vacuum electron traveling wave amplifiers in the 210-220 GHz (G-band) frequency regime. We describe methods that have led to successfully fabricated millimeter wave circuits, including applying ultra-thick SU-8 photoresist layers on copper, copper electroforming solutions, and the challenging removal of the SU-8 photoresists. A table of experimental liquid SU-8 removal chemistries and results is also presented.