Low energy rf sputtering system for the deposition of ITO thin films

An rf-de coupled magnetron sputtering system was used to deposit ITO thin films at a target potential above -100 V. The energy of the ions incident to the target surface during sputtering, i.e., the target cathode potential, was controlled bq means of a de high voltage power supply, and the number of the ions striking the target was controlled by adjusting the input power to the sputtering system from the rf power supply. The frequency of the rf power supply was changed in the range from 10-100 MHz to maintain the target potential above -100 V during sputtering. ITO films were deposited at various target potentials. The resistivity of the film decreased steeply as the target potential increases from -300 to -100 V, and the minimum resistivity was as low as 5 x 10(-4) Omega cm. This decrease in resistivity was caused by an increase in carrier mobility and carrier density in the films. The smoothness of the film surface was also significantly improved by increasing the target potential. (C) 1999 Elsevier Science Ltd. All rights reserved.