IC-Compatible Two-level Bulk Micromachining for RF Silicon Technology

This paper presents a novel two-level silicon bulk micromachining for integration of RF (radio frequency) devices. The RF devices are fabricated at the frontside of Si (100) wafers using conventional IC technology. A post-processing module is applied from the wafer backside. This module provides a blanket ground plane at an optimum position beneath the wafer surface, a front-side contact from the wafer surface to that ground plane and trenches to suppress cross talk through the conductive silicon. Moreover, due to the front-side RF ground contact, compatibility to conventional packaging is maintained. The feasibility of the new postprocess module is demonstrated through the fabrication of microstrip transmission lines and conductor-backed spiral inductors.