Ja. Wells et Nj. Cronin, THEORETICAL-ANALYSIS OF AIR BRIDGING AND BACK ETCHING TECHNIQUES ON THE SHUNT CAPACITANCE OF PLANAR SUBHARMONIC MIXER DIODES, IEE proceedings. Part H, Microwaves, antennas and propagation, 140(6), 1993, pp. 474-480
A detailed analysis of the capacitance of a subharmonic millimetre-wav
e mixer diode is presented. The individual components contributing to
the total capacitance are identified, with values derived for each com
ponent for a 183 GHz Schottky design. A new method is described to det
ermine the shunt capacitance associated with the complicated geometry
of the metal bonding pads for planar diodes. It is shown that this com
ponent can contribute up to 12 fF towards an overall device capacitanc
e of 25 fF for the 183 GHz design. The inclusion of air bridging and b
ack-etching techniques is shown to reduce this value by 70%, resulting
in a lower capacitance, higher cutoff-frequency subharmonic diode dev
ice.