An optimum design of the micromachined RF inductor

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 (0.7 μm SiO₂/ 0.7 μm Si₃N₄/ 0.7 μm TEOS) to enhance the structural rigidity, the inductor can have better signal stability. As compared, the new design of a 5nH micromachined inductor can have less than 45% inductance variation than the conventional one while both devices operate at 8GHz but with 10 m/sec² acceleration. Meanwhile, using a cross shape instead of blanket membrane can also effectively eliminate the inductance variation induced by the working temperature change (20°C to 75°C). 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.