Analysis of Oxide Formation on Ru Thin Films

Ru is often used as the electrical contact material in MEMS. Compared to most other contact materials Ru has advantages due to its native oxide which has properties that result in both low resistance electrical contact and improved hardness. To better understand how to optimize this oxide formation processing techniques, such as RIE, plasma ashing, and annealing in air, were evaluated for their properties. The properties include the film’s stoichiometry, thickness, and geometric structure, which are studied using angle-resolved XPS, TOF-SIMS, and AFM measurements. The Ru films are deposited on SiO₂/Si(100) substrates. Anneals of the as-grown film have been performed at temperatures as high as 600 °C in air and various other parameters were varied for the methods listed. This results in the formation of a surface oxide, which is mainly composed of RuO₂ and some higher order oxides. Performing a RIE or ashing process on the as-deposited Ru film also results in the formation of a thin RuO₂ film with higher order oxides. Analysis indicates that annealing at higher temperatures in air results in the thickest oxide compared to the other processing techniques.