Physical comparison of $HfO2$ transistors with polycrystalline silicon and TiN electrodes

Transistor gate stack systems consisting of atomic layer deposited $HfO2$ with polycrystalline silicon or TiN gate electrodes have been characterized by analytical electron microscopy to elucidate underlying physical contributions to electrical performance differences. High-angle annular dark-field scanning transmission electron microscopy was used to determine film and interface thickness dimensions and chemical analysis depth profiling was obtained from electron energy loss spectra and energy dispersive x-ray spectra. The high-$k$ gate dielectric film system is shown to be influenced by the choice of electrode material with the formation of an $HfO2$-poly-Si interface that increases the dielectric equivalent oxide thickness and may affect electron trapping characteristics.