9.4: MEMS fabrication of 0.22 THz sheet beam TWT circuit

0.22 THz sheet beam traveling wave tube amplifier (TWTA) circuits fabricated by microelectro mechanical system (MEMS) processes are under investigation for submillimeter wave applications. Currently, we are investigating three different methods; KMPR UV-LIGA and nano CNC machining. Eigenmode transient simulations show that, accounting for realistic values of our currently achievable fabrication tolerances, the transmission, and dispersion properties of the operation modes of a TE-mode, staggered, double grating circuit are maintained within less than 1 dB and 2% deviation, respectively. Scanning electron microscopy and atomic force microscopy analyses of the fabricated circuit samples demonstrate that both of the MEMS fabrication approaches produce circuits with ± 3 - 5 μm dimensional tolerance and ~ 30 nm surface roughness. Currently, the fabricated circuits are being cold-tested and process conditions will be re-adjusted with respect to a test result for optimization.