Material characteristics and electrical property of reactively sputtered RuO2 thin films

Thin films of RuO2 were prepared by reactive rf sputtering from a Ru target in an Ar + O-2 atmosphere, with the oxygen concentration varying from 10% to 100%. The resistivity, deposition rate, crystal structure: surface morphology, composition and chemical binding state of RuO2 films were investigated. RuO2 films sputtered with 33% or more oxygen exhibited lower deposition rate and lower resistivity relative to the films sputtered with 10 or 20% oxygen. The O/Ru ratios of the RuO2 films sputtered with 10, 20 and 50% oxygen were similar; however, evident rutile structure was only observed for films sputtered with 50% O-2. The low resistivity is related with the crystallinity of the films. The RuO2 films sputtered with 50% oxygen were annealed in flowing oxygen at 200-750 degreesC for 30 min. The film resistivity was further decreased with increasing annealing temperature and reached a minimum value of 110 mu Ohm cm after annealing at 650 degreesC. From X-ray diffraction and scanning electron microscopy analyses, the decrease of film resistivity upon annealing is attributed to the grain growth and reduction of lattice spacing in the RuO2 films. (C) 2001 Elsevier Science B.V. All rights reserved.