Abstract

Modulated-dc-magnetron sputtering offers a novel solution to problems associated with arcing on the surface of the sputtering target. Arcing has been identified as a main contributor to defects in thin films produced with low-pressure reactive magnetron-sputtering deposition. By biasing the target with a de potential that is modulated at ultrasonic frequencies, sputtering-target arcing is eliminated so that coatings with fewer defects are produced. In the technique presented here, the output from a de power supply is directed into a modulator circuit that switches the output according to a frequency and duty cycle set by a waveform generator. Thus, the output from the modulator is a time-varying electric potential with its most negative value equal to the output of the power supply and its minimum value equal to zero. Arcing on the sputtering target ceases when the switching frequency exceeds a certain threshold value (typically 10-30 kHz) that is dependent on the deposition parameters. Since modulated-dc-magnetron sputtering is effective at frequencies that are significantly less than the standard rf-sputtering frequency of 13.56 MHz, complications in coupling energy between the power supply and the sputtering target are avoided. Therefore, the efficiency of the sputtering process is dramatically improved compared to rf sputtering.

© 1992 Optical Society of America