Characterization of IrOx sputtering for IrO2 and IrO2/Pt bottom-electrode piezoelectric micro-electro-mechanical systems applications

Publication date: 30 September 2017
Source:Thin Solid Films, Volume 638
Author(s): Daniel M. Potrepka, Manuel Rivas, Haibo Yu, Ronald G. Polcawich, Mark Aindow, Glen R. Fox
This study examines the effects of sputter deposition growth conditions on IrO2 thin films developed as electrode layers for Pb(Zr x Ti1-x )O3 piezoelectric Micro-Electro-Mechanical Systems applications. For IrO2 thin-film bottom electrodes sputter deposited on {100}-textured, rutile structure, TiO2 template layers, the effects of substrate temperature, Ar and O2 flow rates, and post-deposition anneal were studied. Additionally, the impact of various IrO2/Pt bilayer structures on electrode properties were investigated. IrO2 bottom electrodes grown on 100-oriented TiO2 at 500°C with an Ar flow rate of 100sccm, O2 flow rate of 60sccm, and a nominal 100nm thickness exhibited a film sheet resistance of 9.2±0.2Ω/sq., surface roughness of 2.3±0.1nm measured over a 2μm×2μm area, and a rutile structure, preferred-{100} crystalline fiber texture normal to the substrate plane. Furnace-anneal treatments on this electrode at 650°C for 30min in 3 SLM O2 improved its sheet resistance to 7.5±0.2Ω/sq., and surface roughness was 4.0±0.1nm. Bilayers of IrO2/Pt grown on TiO2, with IrO2 and Pt thicknesses in the 0–100nm range, were sputter deposited at 500°C. The electrodes had composite sheet resistances in the range of 1.34±0.03Ω/sq. to 9.92±0.25Ω/sq., and surface roughnesses ranging from 1.5±0.1nm to 2.0±0.1nm for 2μm×2μm measurement areas. Scanning Transmission Electron Microscopy verified preferred IrO2 and Pt crystalline fiber textures of {100} and {111}, respectively.