Terahertz Monolithic Integrated Cavity Filter Based on Cyclic Etched SiC Via-Holes

This article presents a terahertz integrated cavity bandpass filter based on cyclic etched silicon carbon (SiC) via-holes. Solutions are discussed in detail, including design, fabrication, and optimization. The fabrication procedures of the integrated filters are specially optimized, which are fully compatible with that of the common terahertz monolithic integrated circuit. The cyclic via-hole etching technique based on inductively coupled plasma (ICP) is proposed, which achieves via-holes with a controllable inclination on SiC substrate. Measurements show that the insertion loss of the cavity integrated filter is only 1.55 dB at 185 GHz, with a relative bandwidth of 9.7%. Two transmission zeros are introduced by the over-moded technique, achieving the out-of-band suppression of the filter higher than 40 dB. Compared with the traditional terahertz cavity filters, the integrated cavity on SiC substrate provides similar electric performances and better integration but with the one-thousandth of the volume.