PROFILING OF THE DIELECTRIC FUNCTION ACROSS AL/SIO2/SI HETEROSTRUCTURES WITH ELECTRON-ENERGY LOSS SPECTROSCOPY

Al/SiO2/Si heterostructures which are typical of actual electronic devices have been studied with high-spatial-resolution scanning transmission electron microscopy. Electron energy loss spectra were recorded over the low-loss region (0 to 100 eV) at 2.5 to 5 nm intervals across interfaces viewed in cross-section. The energy loss function was then obtained from experimental spectra after Fourier-log deconvolution of multiple scattering. Finally, the complex dielectric function and molar polarizability were determined at each point through a Kramers-Kronig transformation and analytical formulae. Profiles across heterostructures show that minima exist in the molar polarizability at the interfaces, which suggests that the interfaces have a lower intrinsic dielectric strength.