Chemical-state resolved depth profile and band discontinuity in TiN/HfSiON gate stack structure with AlO_x cap layer

We have investigated chemical-state-resolved depth profiles and band discontinuity for TiN/HfSiON gate stack structure with an AlO_x cap layer on a Si substrate using backside angle-resolved photoemission spectroscopy. Depth profiles show that Al atoms diffuse through the high-k layer and are accumulated at the high-k/SiO₂ interface during the thermal annealing process. The decrease in relative chemical shift of Si 2p to Hf 4f core-level spectra by inserting the AlO_x cap layer can be explained by the lowering of the valence-band discontinuity, which is induced by the modification of the interface dipole of the high-k/SiO₂ system.