This paper presents a small-signal characterization work on a recently developed 55nm SiGe BiCMOS technology from STMicroelectronics. The SiGe HBT from a prototype BiCMOS 55nm process was investigated up to 325GHz. The full S-parameters from DC to 325GHz under multiple bias conditions are presented for the first time for a SiGe HBT. A usual and simple approach for the off-wafer calibration associated to an on-wafer de-embedding procedure was used and remained valid up to 325GHz thanks to a size reduction of the test structures. The extracted 300/325GHz fT/fMAX couple, reached at 14mA/μm2 collector density and 1.2V collector-emitter voltage, was validated up to 325GHz.