CRYSTALLINITY AND ELECTRICAL-PROPERTIES OF TIN-DOPED INDIUM OXIDE-FILMS DEPOSITED BY DC MAGNETRON SPUTTERING

ITO films with thicknesses between 1000 and 8000 angstrom were deposited on glass substrates at 400-degrees-C by DC magnetron sputtering. The electrical and structural properties were compared to the same properties in evaporated ITO films and ITO powder using ESCA, SEM and X-ray diffraction. The resistivity decreased from 1.92 x 10(-4) to 1.46 x 10(-4) OMEGA-cm as the thickness increased from 1140 to 7620 angstrom, due mostly to a monotonic increase in the carrier density. The (400) plane spacing in the films was higher than in pure In2O3 powder. However, the difference between the (400) plane spacings in the In2O3 and the films decreased as the film thickness increased, from 0.87% in an 1140 angstrom thick film to 0.54% in a 7620 angstrom thick film. For an EB evaporated ITO film having a thickness of 3860 angstrom, the spacing was 0.24% larger than in pure In2O3. X-ray diffraction analysis based on the integral breadth method demonstrated a clear positive correlation between random strain and uniform strain. The decrease of strain and of lattice constant with increasing thickness led to the conclusion that the increased carrier density in thicker films is due to an improvement in crystallinity, which leads to a higher density of electron donor centers.