edfas.org 9 ELECTRONIC DEV ICE FA I LURE ANALYSIS | VOLUME 25 NO . 1 SCANNING MICROWAVE IMPEDANCE MICROSCOPY: OVERVIEW AND LOW TEMPERATURE OPERATION Nicholas Antoniou PrimeNano Inc., Santa Clara, California nicholas@primenanoinc.com EDFAAO (2023) 1:9-13 1537-0755/$19.00 ©ASM International® INTRODUCTION Scanning microwave impedance microscopy (sMIM) is a relatively recent technology that was invented at Stanford University by Shen and Kelly.[1] It has been commercialized by PrimeNano Inc. as ScanWave and is currently available in five different configurations from room temperature to ultra-low (mK) temperature operation. sMIM is a near-field technique utilizing microwaves to probe the electrical properties of materials such as conductivity and permittivity with nanoscale lateral resolution. Its unique advantage is that electrical property information can be obtainedwithout the use of an electrical current flow through the sample. This not only makes sample preparation simple, but one can image floating dielectrics with no grounding, and image sub-surface features. In Fig. 1, buried islands of silicon dioxide in a sea of silicon nitride are highlighted because of the sensitivity of the systemto permittivity changes in a scanned area. To achieve nanoscale resolution, a customprobe ismounted onto an atomic force microscope (AFM) that enables 2D and 3D image acquisition of relative permittivity, conductivity, and topography information. Low temperature sMIM systems were recently introduced to the market that operate from sub 100 mK to 2 K, with vector magnets and an ultra-high vacuum option. The ability tomeasure the electrical properties of materials at varying temperatures has led to many discoveries such as superconductivity, quantumhall effect, fractional quantum hall effect, giant magnetoresistance, and graphene. Quantum computing research is also benefiting from this low temperature capability as the properties of materials used in quantum computing are often analyzed at the low temperatures at which they operate. This Fig. 2 sMIM system schematic outlining the basic principle of operation. Fig. 1 sMIMcapacitance image (sMIM-C in volts on Z axis) of SiO2 islands buried under 60 nm of Si3N4.
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