Electromagnetically shielded high-Q CMOS-compatible copper inductors

On-chip inductors are valuable components in radio-frequency (RF) circuits, which find widespread applications in wireless communication. The performance of current on-chip spiral inductors generally suffers from low quality factor (Q), the detrimental coupling between the device and its ambient via the silicon substrate, and the lack of a good RF ground plane because of the lossy substrate. A solution to these issues is to build a suspended spiral inductor over a cavity whose bottom plane and side-walls are metallized. The deep cavity can dramatically reduce the electromagnetic coupling and the parasitic capacitance between the inductor and the substrate, increasing Q and the self-resonant frequency.