Electrical properties of Ru and RuO2 gate electrodes for Si-PMOSFET with ZrO2 and Zr-silicate dielectrics

In this work, we have studied the electrical and thermal stability of Ru and RuO2 electrodes on ZrO2 and Zr-silicate dielectrics. Very low resistivity Ru and rutile stoichiometric RuO2 films, deposited by reactive sputtering, were evaluated as gate electrodes on ultrathin ZrO2 and Zr-silicate (∼2.7 nm) films for Si-PMOS devices. Thermal and chemical stability of the electrodes were studied at annealing temperatures up to 800°C in N2 followed by a forming gas anneal. X-ray diffraction (XRD), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS) methods were used to study grain structure and interface reactions. Electrical properties were evaluated using MOS capacitors. The role of oxygen in these dielectrics was studied by comparing equivalent oxide thickness (EOT) changes as a function of annealing temperature for capacitors with ZrO2 and Zr-silicate dielectrics. For capacitors with Ru and RuO2 gate electrodes on both ZrO2 and Zr-silicate, excellent stability of EOT was detected. Flatband voltage and gate current as a function of annealing temperature were also studied. These studies indicate that Ru and RuO2 are promising gate electrodes for P-MOSFETs.