Thin Film Engineering of Indium Tin Oxide: Large area flat panel displays application

Indium Tin Oxide (ITO) thin films with a variety of microstructures were deposited using a large area conventional DC magnetron sputtering system for flat panel displays manufacturing. Highly uniform ITO films with an average thickness of ∼100 ± 3 nm on the ∼0.6 m2 substrate area were obtained. Film structures with small amounts of crystalline sites were produced by room temperature deposition, and an entirely amorphous structure with excellent etching properties was achieved through optimized incorporation of hydrogen in the film, providing a significant increase in the crystallization temperature of ITO. Post-annealing of such a sample yielded a randomly orientated polycrystalline structure with superior conductivity and transparency. The polycrystalline ITO films, produced at the sputtering substrate temperature of 200 °C, provided structures with preferential grain orientation in both <111> and <100> directions, controlled by the amount of oxygen and increased process pressure. The impact of oxygen and pressure with related structures on the macroscopic properties of the layers was studied. Morphological features of the films such as phase/grain structure and surface roughness were investigated using SEM and AFM. Layers with an equiaxed grain structure of about 30 nm crystal size revealed an ultra smooth surface with RMS values of about 1 nm. Specific resistivities as low as 150 μΩ cm and transmittance values above 92% at 550 nm wavelength were obtained for polycrystalline layers with preferential grain orientation.