High performance MEMS 0.18 μm RF-CMOS transformers

This work presents the application of a front-side maskless MEMS process to improve the performance of RF-CMOS transformers. High-frequency parasitic effects are much diminished, as oxide and substrate material are etched away. The passivated metal surface prevents damage to the transformer, and to other circuits, which use metal layers as self-aligned etch masks. Device self-resonant frequency was improved by 20%. At 18 GHz, device quality factor rose from 0.5 to 6, and at 50 GHz, maximum available gain was increased by 49%. The process's low cost relative to other MEMS optimization methods with similar results makes this process attractive for the use of transformers in system-on-chip design.