Study On Preparation Of Vanadium Oxide Thin Films On Different Substrates Using Facing Targets DC Reactive Sputtering Technique

As the detecting material of uncooled infrared detectors, vanadium oxide (VOX) thin films need high temperature coefficient of resistance (TCR) and suitable film resistance for using of the device. In this paper, vanadium oxide thin films were prepared on glass substrate, SiO₂/Si substrate, silicon nitride substrate and porous silicon substrate with facing targets DC reactive sputtering technique. The VOX thin films have high TCR values, suitable film resistances and good structure performance.The effects of the parameters including ratio of Ar/O2, sputtering power, sputtering time, working pressure and substrate temperature on the performance of vanadium oxide thin films are analyzed by choosing different level of these parameters in the orthogonal experiment. The optimal deposition parameters of VOX thin films were defined as follow: on glass substrate, working pressure: 2.0 Pa, gas flow ratio: Ar:O2 =48sccm:0.4sccm, substrate temperature: room temperature, sputtering power: 210W-240W, sputtering time:30 minutes; On SiO₂/Si substrate, working pressure: 2.0 Pa, gas flow ratio: Ar:O₂ =48sccm:0.4sccm, substrate temperature: room temperature, sputtering power: 180W-210W, sputtering time:30 minutes; On silicon nitride substrate, working pressure: 2.0 Pa, gas flow ratio: Ar:O2 =48sccm:0.5sccm, substrate temperature: 200℃, sputtering power: 210W, sputtering time:30 minutes; On porous silicon substrate, working pressure:1.0 Pa, gas flow ratio: Ar:O₂ =48.5sccm:1.5sccm, substrate temperature: 400℃, sputtering power: 210W-220W, sputtering time:60 minutes. The TCR values of the samples on the four different substrates were all high up to -3%/℃and the sheet resistance was under 50KΩ/□around room temperature. The VOX thin films on the porous silicon substrate presented the phase changing performance.Atomic force microscopy(AFM) surface morphology indicated a planar and compact film surface. X-ray photoelectron spectroscopy(XPS) analysis revealed the vanadium oxygen state of the film, which included V₂O₅,VO₂ and a few V₂O₃. TCR becomes higher (lower) as the higher (lower) sheet resistance due to the higher (lower) content of VO₂.The annealing experiment of the samples on glass substrates and SiO₂/Si substrates indicated that annealing could improve the VO_X thin film structure and their TCR value, while the high sputtering power could damaged the VO_X thin film structure.