Characterization of Ti/W, Ti/Cr, and Ti/Pt thin films−part І: Surface morphologies and nano-mechanical properties

Metallization used for MEMS devices operated in physical contact mode should have high scratch and wear resistance as well as a high mechanical strength. This paper, Part І in a two-part series, investigates the surface morphologies, surface roughness, electrical, and nano-mechanical properties of Ti/W, Ti/Cr, and Ti/Pt thin films annealed at various temperatures. W, Cr, and Pt films were formed on the silicon substrate where SiO2 as an insulation layer and Ti as an adhesion layer had already been deposited. Then, the thin films were annealed at 400, 500, and 600 °C for 1 h in N2. The experimental results indicate that the Ti/W film annealed at 400 °C has relatively low electrical resistivity and roughness values and high hardness and elastic modulus values. The Ti/Cr films were very easily oxidized during the annealing process and had high resistivity and surface roughness values. The Ti/Pt films were not oxidized at all during the annealing process, which indicates that the Ti/Pt films can be used for MEMS devices operated in a high-temperature air atmosphere. However, the Ti/Pt film annealed at 600 °C cannot be used for metallization as hillocks were found to protrude from the surface of the film after the annealing process. This resulted in very rough surface features and diminished wear resistance.