Paper TF-ThP4
Al-doped ZnO (AZO) Films Deposited by Gas Flow Sputtering for Transparent Conductive Thin Films

Thursday, October 18, 2007, 5:30 pm, Room 4C

Al-doped ZnO (AZO) has been attracted much attention as one of alternative materials to Sn-doped In₂O₃ (ITO) films. Recently, there have been strong demand for high deposition rate with stable discharge and low cost deposition systems for the various commercial applications. Gas Flow Sputtering (GFS) has two important features. The one is the possibility for very high deposition rate because of using an intense hollow cathode discharge and a large amount of sputtering gas (Ar) flow. Another is stability of the reactive sputtering process with the variation in reactive gas (O₂) flow. Reactive sputtering is usually highly nonlinear processes for the conventional glow discharge sputtering because of the poisonings of the target surface. In the case of GFS, a large amount of Ar gas flows from the faced targets to the substrate preventing the oxidation of the target surface. AZO films were deposited by GFS on alkali-free glass (corning, #1737) without heating using two Zn-Al alloy targets (Al: 1.5 wt.%). For all the depositions, Ar gas flow and sputtering power were fixed at 1.0 SLM and 1500 W, respectively. O₂ flow was controlled from 0 to 10 sccm. The crystal structure was analyzed by X-ray diffraction (XRD). The electrical and optical properties were measured by van der pauw method and UV-IR spectroscopy, respectively. With increasing O₂, the intensity of an XRD peak of Zn metal decreased. On the other hand, ZnO XRD peaks appeared from O₂ flow of 6 sccm. All AZO films deposited over 6 sccm of O₂ exhibited a strong c-axis preferred orientation perpendicular to the substrate surface. Deposition rate was about 70 nm/min. At O₂ gas flow of 6 sccm, the AZO film showed the lowest resistivity of 9.82×10^-4 Ω cm, Hall mobility of 10 cm²/V s, carrier density of 5.48×10²⁰ /cm³.