Loss Analysis of Thin Film Microstrip Line With Low Loss at D Band

The D-band (110~170 GHz) thin film microstrip line (TFML) with easy integration, low loss, and easy fabrication is presented in this work. It is composed of copper (Cu) signal line on the top layer, ultra-thin Benzocyclobutene (BCB) dielectric on the interlayer and Cu ground plate on the bottom. This study presents the calculation formulas, extraction methods, reduction solutions of metal loss, dielectric loss, and radiation loss. The calculation results well agree with the simulation results. Metal loss caused by skin effect and surface roughness is the main part of loss, accounting for 89%. The introduced micro-electro-mechanical-systems (MEMS) process could precisely manufacture samples in batches. The tested loss after thru-reflect-line (TRL) de-embedding is 0.6 dB/mm, which is higher than the simulated loss of 0.4 dB/mm. The simulated loss corrected after considering the roughness effect has good agreement with the tested loss. The proposed TFML and its loss analysis help to design planar passive devices with low loss at D band.