An optimum design of the micromachined RF inductor

Abstract

With a complete performance investigation of the on-chip micromachined inductor with mechanical disturbances using ANSYS and HFSS simulators, an optimum structural design of the micromachined spiral inductors with fully CMOS compatible post-processes for RFIC applications is proposed in this paper. Via the incorporation of a sandwich dielectric membrane (0.7mum SiO2/ 0.7mum Si3N4/ 0.7mum TEOS) to enhance the structure rigidity, the inductor can have better signal stability. As compared, the new design of a 5nH micromachined inductor can have less 45% inductance variation than the conventional one while both devices operate at 8GHz but with 10 m/sec(2) acceleration. Meanwhile, using a cross shape instead of blanket membrane can also effectively eliminate the inductance variation induced by the working temperature change (20degreesC to 75degreesC). It's our belief that the new micromachined inductors can have not only high Q performance but also better signal stability suitable for wide range RFIC applications.