The effect of process parameters on the properties of tin-doped indium oxide thin film, deposited by magnetron sputtering with simultaneous application of r.f. and d.c. power, has been investigated. Introduction of impurity atoms originated from residual air in the chamber, by intentional high sputtering base pressure, produced the change in lattice as well as microstructure of the ITO film. Sputter deposition with higher sputtering base pressure resulted in lower resistivity of the film. An increase in the mobility of the carrier resulted in a resistivity decrease. Resistivity as low as 1.5 x 10(-4) Ohm cm has been achieved with d.c. 0.67 kW cm(-2) and r.f. 0.67 kW cm(-2) power density and 10(-5) Torr sputtering base pressure at 200 degrees C. X-ray diffraction analysis showed as much as 0.2% increase in lattice constant resulting from higher base pressure sputtering. No further improvement of conductivity was observed for the sputtering base pressure over 10(-5) Torr, suggesting impurity introduction saturation into the film. Deposition at a substrate temperature lower than 150 degrees C resulted in the formation of an amorphous phase, adversely affecting the electrical and optical properties for opto-electronic applications.