Band bendings of Si substrates have been observed using hard x-ray photoemission spectroscopy. With a capability of collecting photoelectrons generated as deep as 40 nm, the binding energy shift in a core level caused by the potential profile at the surface of the substrate results in a spectrum broadening. The broadening is found to be significant when heavily doped substrates are used owing to its steep potential profile. The surface potential of the substrate can be obtained by deconvolution of the spectrum. This method has been applied to observe the band bending profile of metal-oxide- semiconductor capacitors with high- k gate dielectrics. By comparing the band bending profiles of heavily-doped n+ - and p+ -Si substrates, the interface dipoles presented at interfaces can be estimated. In the case of W gated La2 O3 /La -silicate capacitor, an interface dipole to shift the potential of -0.45 V has been estimated at La-silicate/Si interface, which effectively reduces the apparent work function of W. On the other hand, an interface dipole of 0.03-0.07 V has been found to exist at Hf-silicate/ SiO2 interface for W gated HfO2 /Hf-silicate/ SiO2 capacitor.
ASJC Scopus subject areas
- Physics and Astronomy(all)