CMOS-MEMS integrated scanning microwave microscopes

We present, for the first time, the design, fabrication and experimental validation of a CMOS-MEMS scanning microwave microscopy (SMM) system. A flexible micro-coaxial transmission line is collocated with an AFM probe on a single CMOS-MEMS chip and is scanned by integrated electrothermal actuators with integrated position sensors. The microwave/AFM tip can be scanned over the sample in 3 degrees of freedom, over a 20μm × 10μm × 30μm scan range in the x, y, and z directions respectively. SMM devices with integrated 3-DoF actuation fabricated with post-CMOS MEMS integration are then introduced. These devices can be used to modulate the tipsample separation with a periodic signal, enabling the use of lock-in techniques to improve immunity to long-term system drifts. To increase measurement sensitivity further, a single-stub matching network has been used to match the high tip-to-sample impedance to the 50-ohm characteristic impedance of the measurement system. Measurement results of the CMOS-MEMS SMM are presented to verify the proposed concept.