Electrical characterization of gate oxides by scanning probe microscopies

Ballistic electron emission microscopy (BEEM) and non-contact atomic force microscopy (NC-AFM) are used to characterize SiO2 and Al2O3 layers grown on Si(1 0 0). The effective conduction band mass and its energy dispersion in SiO2 and an offset between Al2O3 and Si conduction bands of 2.78 eV were obtained with BEEM. NC-AFM was used to image electrons, and in some instances holes, trapped in the oxide layers near the surface and in the bulk of the oxide. Modeling of the tip-surface interaction supports the interpretation of image features arising from a single electron occupying a trap. The polarity of the trapped charge was deduced from Kelvin (potential difference) images that were simultaneously recorded with the topographic images. © 2002 Elsevier Science B.V. All rights reserved.