Conducting atomic force microscopy for nanoscale electrical characterization of thin SiO2

In this work, we demonstrate the applicability of conducting atomic force microscopy (AFM) for the quantitative electrical characterization of thin (3- 40 nm) SiO2 films on a nanometer scale length. Fowler- Nordheim (F-N) tunneling currents on the order of 0.02-1 pA are measured simultaneously with the oxide surface topography by applying a voltage between the AFM tip and the silicon substrate. Current variations in the F-N current images are correlated to local variations of the oxide thickness on the order of several angstroms to nanometers. From the microscopic current-voltage characteristics the local oxide thickness can be obtained with an accuracy of +/-0.3 nm. Local oxide thinning of up to 3.3 nm was found at the edge between gate oxide and field oxide of a metal-oxide-semiconductor capacitor with a 20-nm-thick gate oxide. (C) 1998 American Institute of Physics. [S0003-6951(98)01247-9].