Copper/Benzocyclotene Thin Film Technique Based Microstrip Bandpass Filter Featured By Thick Dielectric Layer For Low Insertion Loss

In this paper, a copper/benzocyclotene thin film based microstrip bandpass filter featured by a thick dielectric layer is presented. For thickening dielectric layer, a 30 mu m-deep micromachined groove with embedded benzocyclotene polymer is fabricated on the surface of silicon substrate. Mechanical polishing is utilized to planarize the benzocyclotene polymer embedded in the groove. Atomic Force Microscopy is used to characterize the surface roughness of benzocyclobutene (BCB) polymer film before and after polishing. With two additional BCB layer, a total thickness of 75.4 mu m dielectric layer is realized, and the insertion loss of the filter can be reduced by 1.34 dB theoretically. The measured insertion loss of fabricated filter is -2.2 dB, which can be further reduced via tighter control of device parameters.