Promising Gate Stacks with Ru & RuO2 Gate Electrodes and Y-silicate Dielectrics

Abstract

ABSTRACTIn this work, we studied the electrical and thermal stability of Ru and RuO2 electrode on Y-silicate dielectrics in contrast to ZrO2 and Al2O3 dielectrics. Very low resistivity Ru and rutile stoichiometric RuO2 films, deposited via reactive sputtering, were evaluated as gate electrodes on ultrathin Y-silicate, ZrO2 and Al2O3 films for Si-MOS devices. Thermal and chemical stability of the electrodes was studied at annealing temperatures up to 800°C in N2 and subsequently forming gas anneal. XRD and XPS were measured to study grain structure and interface reactions. The morphology of the films was tested by atomic force microscopy (AFM). Electrical properties were evaluated via MOS capacitors. The role of oxygen inside dielectrics was studied by comparing equivalent oxide thickness change as a function of annealing temperature for capacitors with Y-silicate, ZrO2and Al2O3 dielectrics. Good stability of Ru and RuO2 gate electrodes on all dielectrics studied was found. Flatband voltage and gate current as a function of annealing temperature was also studied. It was found that capacitors with Y-silicate after high-temperature anneal had less positive flatband voltage shift than ZrO2 and Al2O3. For capacitors with Ru gate electrode, the significant flatband voltage shift after high temperature anneal could be partially removed by a forming gas anneal.