Characterization of conductive probes for atomic force microscopy

Abstract

The availability of very sharp, wear-proof, electrically conductive probes is one crucial issue for conductive Atomic Force Microscopy (AFM) techniques such as Scanning Capacitance Microscopy (SCM), Scanning Spreading Resistance Microscopy (SSRM) and Nanopotentiometry. The purpose of this systematic study is to give an overview of the existing probes and to evaluate their performance for the electrical techniques with emphasis on applications on Si at high contact forces. The suitability of the charactensed probes has been demonstrated by applying conductive AFM techniques to test structures and state-of-the-art semiconductor devices.Two classes of probes were examined geometrically and electrically: Si sensors with a conductive coating and integrated pyramidal tips made of metal or diamond. Structural information about the conductive materials was obtained by optical and electron microscopy as well as by AFM roughness measurements. Swift and non-destructive procedures to characterise the geometrical electrical properties of the probes prior to the actual AFM experiment have been developed. A number of analytical tools have been used to explain the observed electrical behaviour of the tested probes.