Scanning kelvin force microscopy for characterizing nanostructures in atmosphere

Abstract

The Electrostatic Force Microscope (EFM) and the related Scanning Kelvin Force Microscope (SKFM) are of interest for the measurement of potential distributions within nanostructures and for work function measurements of gate metals for next generation CMOS. EFM phase mode has better spatial resolution than SKFM because its signal depends on the electric field gradient, while the SKFM's signal depends on the electric field directly. We have determined the effect of data acquisition conditions on spatial resolution and accuracy of CPD measured with SKFM in atmosphere by using various commercially available tips and a specially designed test chip containing up to four different metal layers. The test chip contains structures intended to simulate nanoparticles and nanowires in various combinations of metals. By comparison to measurements on the test structures using tips with known work functions, the effective work functions of tips with unknown work functions can be estimated. A simple computer model was developed that predicts SKFM signal as a function of tip and sample measurement geometries. Qualitative agreement between the measured and modeled SKFM signal is seen. © 2007 American Institute of Physics.