Comparative study on structure and internal stress in tin-doped indium oxide and indium-zinc oxide films deposited by r.f. magnetron sputtering

Mechanical properties such as internal stress or adhesion of transparent conductive oxide (TCO) films are important in order to guarantee the patterning accuracy and durability for various types of commercial applications. Representative TCO films, such as tin-doped indium oxide (ITO) and indium-zinc oxide (IZO) films, were deposited on unheated glass substrate by r.f. magnetron sputtering using corresponding oxide targets under various total gas pressures (Ptot) ranging from 0.3 to 3.0 Pa. The internal stresses in these TCO films were measured by the cantilever method in relation to the total gas pressure during the deposition. The ITO films deposited at a Ptot lower than 0.7 Pa were polycrystalline and were found to have large compressive stress, whereas the amorphous ITO films deposited at 1.5–3.0 Pa were found to have a very low tensile stress. In contrast, all IZO films, of various thicknesses (50–750 nm), deposited at a Ptot of 0.3–3.0 Pa were found to have an entirely amorphous structure. The compressive stress in IZO films was lower than that in ITO films, especially for the low working pressure depositions.