RuO2/Ru electrode on Si3N4/Si substrate for microelectromechanical systems devices based on Pb(Zr1-xTix)O-3 film and surface micromachining

Abstract

RuO2/Ru conducting films were deposited on low stress Si3N4/Si substrates by reactive r.f. sputtering deposition at a substrate temperature of 400 degrees C to introduce a new bottom electrode for microelectromechanical system devices based on a Pb(Zr1-xTix)O-3 film and a surface micromachining technique with high temperature processes. X-ray diffraction and scanning electron microscopy measurements after heat treatment at 700 degrees C were conducted to investigate structural stability of the RuO2/Ru films, which showed no silicide and silicon oxide formations by the heat treatment. Interfacial structures of the film with the heat treatment were similar to those of the as-deposited films. The surface of the film with the heat treatment consisted of larger grains than those of the as-deposited film. Rutherford backscattering spectrometry and Auger electron spectroscopy showed no interfacial reactions between the RuO2/Ru and the Si3N4 In order to investigate the feasibility of the RuO2/Ru as a bottom electrode, Pb(Zr0.53Ti0.47)O-3 films were deposited by metalorganic decomposition. After deposition of a Pb(Zr0.53Ti0.47)O-3 film at 700 % for 30 min, the interface structure between the RuO2/Ru and the Pb(Zr0.53Ti0.47)O-3 film showed no interface reactions. The electrical properties of the PZT film on the RuO2/Ru were not changed before and after an HF etching to make an air gap, even though the piezoelectric coefficients on the RuO2/Ru were lower than on the Pt/Ti. Therefore, the RuO2/Ru conducting film could be used for a bottom electrode on the Si3N4/Si for a microelectromechanical system device based on a Pb(Zr1-xTix)O-3 film and a surface micromachining technique with high temperature processes.