Wafer-level integration of on-chip antennas and RF passives using high-resistivity polysilicon substrate technology

Abstract

High-resistivity polycrystalline silicon (HRPS) wafers are utilized as low-loss substrates for three-dimensional integration of on-chip antennas and RF passive components (e.g. large inductors) in wafer-level chip-scale packages (WLCSP). Sandwiching of HRPS and silicon wafers enables to integrate large RF passives with a spacing of >150 µm to the conductive silicon substrate containing the circuitry, while providing mechanical stability, reducing form factor and avoiding any additional RF loss. Antenna performance comparable to glass substrates and high quality factors for large spiral inductors (Q=11 at 1 GHz; 34 nH) are demonstrated. The HRPS substrates have high dielectric constant, low RF loss, high thermal conductivity, perfect thermal matching, and processing similar to singlecrystalline silicon.