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 /spl mu/m SiO/sub 2// 0.7 /spl mu/m Si/sub 3/N/sub 4// 0.7 /spl mu/m 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/sec/sup 2/ acceleration. Meanwhile, using a cross shape instead of blanket membrane can also effectively eliminate the inductance variation induced by the working temperature change (20/spl deg/C to 75/spl deg/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.

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