Conductive atomic-force microscopy investigation of nanostructures in microelectronics

Abstract

Conductive atomic-force microscopy (C-AFM), where a conductive, biased probe is scanned in contact mode across the surface under investigation is one of the most prominent scanning probe microscopy based techniques to study electrical properties of dielectric and semiconducting thin films on the nanometer scale. The technique, originally developed to evaluate the homogeneity in gate dielectrics is also successfully applied to study electrical and electronic properties of semiconductor nanostructures. The chapter starts with the discussion of the technical implementation of the technique (both under ambient conditions and in ultra-high vacuum) and the experimental peculiarities due to contact mode. The concepts of two-dimensional current maps acquired at constant tip-to-sample bias and local current voltage maps will be introduced for the example of thin silicon gate oxide and high-k dielectric thin films. Applicability of C-AFM to semiconductor nanostructures is demonstrated for supported semiconductor nanowires and free standing nanorods. Characterization of antiphase defects in ternary alloys and ZnO based multilayer varistor films show the technique's potential for device evaluation. An outlook is devoted to the so-called photoconductive AFM where photocurrents are detected under simultaneous illumination with monochromatic light.