Sun, XiaoXiaoSunSinha, SiddharthaSiddharthaSinhaHuynen, MartijnMartijnHuynenBroucke, ReinierReinierBrouckeLofrano, MelinaMelinaLofranoCherman, VladimirVladimirChermanJafarpoorchekab, HamidehHamidehJafarpoorchekabLeech, DamienDamienLeechUruena, AngelAngelUruenaShafahian, EhsanEhsanShafahianPinho, NelsonNelsonPinhoChancerel, FrancoisFrancoisChancerelKennes, KoenKoenKennesLemey, SamSamLemeyMiller, AndyAndyMillerBeyne, EricEricBeyneCollaert, NadineNadineCollaert2026-03-242026-03-242025979-8-3315-3933-70569-5503https://imec-publications.be/handle/20.500.12860/58936This paper presents an advanced RF silicon interposer platform that integrates high-Q passive components and flip-chip InP die for wideband high frequency applications. By spin coat low-loss RF polymer (CYCLOTENE™ XP80) on top of the thick metal redistribution Layers (RDLs) for signal routing, the platform achieves low insertion loss, excellent impedance control, and high integration density. Measured insertion losses are 0.23 dB/mm at 140 GHz, 0.5 dB/mm at 220 GHz, and 0.73 dB/mm at 325 GHz, demonstrating state-of-the-art performance. Dielectric characterization using antenna-and resonator-based methods determines a relative permittivity of approximately 2.55 (±1.5%) across the 110–325 GHz frequency range. An integrated InP power amplifier (PA) on the interposer demonstrates a 3 dB bandwidth of 116–148 GHz, a peak gain of 16.3 dB, and P1dB values ranging from 13 to 15 dBm, with a power-added efficiency (PAE) of 15–28% within the 125–135 GHz range. Furthermore, a strong correlation between thermal sensor measurements and FEM simulations enables the extraction of XP80's thermal conductivity, which is essential for effective thermal management. These results underscore the advancement of a state-of-the-art RF interposer platform optimized for heterogeneous integration in mmWave and sub-THz applications.engProceedings paper10.1109/ECTC51687.2025.00038WOS:001537918100033