Scanning microwave microscope (SMM) combines the high spatial resolution with the high-sensitivity electric measurement capabilities of a vector network analyzer (VNA). SMM has been pointed out as very well suited for nanodevices characterization. In recent publications, SMM has demonstrated high performance while measuring kO-range impedances at low microwave frequency range (1-20 GHz). In spite of exceptional results, interferometry-based systems are so far hardly feasible as an integrated circuit due to physical constraints. In this work, an innovative design of integrated reflectometer based on BiCMOS 55 nm technology from STMicroelectronics is proposed. Electrical simulation results have proved a linear tuner calibration from 0.9 to 1.4 fF with an 8-bits precision (i.e. 2.0 aF). Reflectometer performance has been considered under influence of temperature variation from -55 to 125 degrees C and process variability. Such results demonstrate a slight influence of temperature variation and process variability in the reflectometer calibration which is negligible for SMM applications.