Evaluating probes for “electrical” 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, scanning spreading resistance microscopy, 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 characterized 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 electron microscopy and other analytical tools. Swift and nondestructive procedures to characterize the geometrical and electrical properties of the probes prior to the actual AFM experiment have been developed. Existing contact models have been used to explain variations in the electrical performance of the conductive probes.

Nanoscale electronic noise measurements

“…The stability of the electrical contact between tip and surface is a crucial issue for conductive AFM measurement [5]. Particularly, noise measurements require a longterm stable contact during the whole averaging time.…”

Conducting-Atomic Force Microscopy Investigation of the Local Electrical Characteristics of a Ti/TiO[sub 2]/Pt Anode

“…Of key importance to these local electrical measurements is the preparation of the conducting tip. [3][4][5] This typically involves either coating a conventional Si 3 N 4 or Si AFM probe with a thin conducting film ͑typically Pt or Au of ϳ10 to 50 nm thickness͒ 3,6 or heavily doping either the probe or a hard wearing film, such as diamond, deposited on the probe. 4,7,8 The contact resistance of this latter type of probe is normally greater than for a metal-coated tip.…”

Characterization of silicon gate oxides by conducting atomic force microscopy

“…Because of the low resistivity and the high wear resistance necessary to scan over the hard silicon oxide surfaces in contact mode, silicon cantilevers with a borondoped diamond coating of the tip have been used. 11 Attempts with PtIr or WC tips were not as successful. Both PtIr and WC tips provided a wear resistance, that was too low, causing changes in the tip geometry that made consistent measurements impossible.…”