单芯片扫描微波显微镜

We present the design, fabrication and experimental validation of an integrated Scanning Microwave Microscopy (SMM)/Atomic Force Microscopy (AFM) system that does not require the use of a conventional laser-based AFM. Microfabricated SMM probes are collocated with piezoresistive strain-based sensing AFM probes in a CMOS-MEMS process, and are actuated by integrated electrothermal scanners. Integration of AFM enablesdualmodeimaging(topographyandelectricalproperties) andmoreimportantly,itenablescontrolovertip-sampledistance, whichiscrucialforaccurateSMMimaging.Thisdesignisunique in the sense that the tip can be scanned over the sample in 3 degreesoffreedom,overa scanrange in the x, y, and z directions respectively. We fabricate our device by using a standard foundry CMOS process followed by in-house masklessMEMSpostprocessingtoreleasethedevices.Single-chip SMM/AFMdeviceswithintegrated1-Dand3-Dactuationarethus obtained. These devices can be used to modulate the tip-sample separationtounderlyingsampleswithaperiodicsignal,improving immunitytolong-termsystemdrifts.Wealsoinvestigatetheeffect of tip-sample separation on the resolution of the instrument. To increase measurement sensitivity, a single-stub matching network has been used to match the high tip-to-sample impedance to the 50 ohm characteristic impedance of a performance network analyzer. Measurement results of the CMOS-MEMS SMM are presented to verify the proposed concept.