In this work, a Conductive Atomic Force Microscopy (CAFM) working in contact mode has been used to compare the measured electrical properties and breakdown (BD) on ultra thin high-k dielectrics, when different environmental conditions are used. In particular, the effect of the environment on the conductivity measurements, the lateral resolution in current images and the lateral propagation of the BD event will be analyzed in air, dry nitrogen (N2) and Ultra High Vacuum (UHV).

Conductive atomic force microscopy experiments on gate dielectrics in air, nitrogen, and UHV have been compared to evaluate the impact of the environment on topography and electrical measurements. In current images, an increase of the lateral resolution and a reduction of the conductivity were observed in N2 and, especially, in UHV (where current depends also on the contact force). Both effects were related to the reduction/elimination of the water layer between the tip and the sample in N2/UHV. Therefore, since current measurements are very sensitive to environmental conditions, these factors must be taken into consideration when comparisons between several experiments are performed.

This work concerns deeply bound charge centers in ultra thin high-k films. Non-contact Atomic Force Microscopy was used to simultaneously image topology and electric force data arising from unscreened fixed charges. These charges were produced using synchrotron radiation to pump Si L and K shell transitions. Defect charging then results from electron transfer between a defect state and a core hole state. We were able to demonstrate the local detection of x-ray absorption spectra using the probe tip. This enabled us to establish a possible link between film morphology, electronic defects and local stoichiometry in ultra thin high-k films on the nm scale.

The interaction between sub-surface charge and the physics of the tunnelling process has been studied for a number of doped semiconductor structures. The work was carried out using a UHV STM and measurements were made in two dimensions on (110) surfaces cleaved in UHV. It is clear that for such surfaces, tunnelling spectra, and hence the tip movement traditionally used to generate topology images, depend on the sub-surface depletion beneath the tip. The influence of the semiconductor screening properties and its impact on dopant related image-formation is discussed.