A study of indium tin oxide thin film deposited at low temperature using facing target sputtering system

Abstract

Indium tin oxide (ITO) thin films, for electroluminescent display electrodes, must be of low resistivity and high transparency. In this study, a facing target sputtering system was used to fabricate this film in order to improve its electrical and optical properties. Temperature was one of the most critical factors during fabrication. Scanning electron microscopy (SEM) and X-ray diffraction XRD were used to analyze the surface morphology and structure of ITO thin films. It was concluded that the ITO films deposited between 50 and 200 °C were polycrystalline. Under 50 °C, the ITO films were amorphous or had mixed amorphous and crystalline phases. After post-annealing, the amorphous ITO films could become crystalline, and therefore, the electrical property of amorphous ITO films could be effectively improved. In this research, an ITO film with the resistivity as low as 1.99×10 −4 Ω cm and transparency above 85% within the visible wavelengths 400∼800 nm, was obtained after vacuum annealing at 300 °C for 2 h, while deposited at a working pressure 0.1333 Pa, percentage oxygen flow rate 22.7% in Ar+O 2 gas mixture, substrate temperature 75 °C, and input DC power 50 W for 30 min. The corresponding deposition rate for this film was 22 nm/min.