High rate radio frequency sputtering using in-phase plasma confinement

Abstract

A new new radio frequency sputtering system single-wafer (125 mm diam) design has been developed to achieve low-voltage sputtering at high power density without magnetic confinement. The low voltage operation was achieved by using in-phase target and substrate sheath voltages, 40.68 MHz excitation, and a controlled-area confining wall electrode. A single generator was used with a simple bias adjustment circuit to obtain in-phase excitation. Observed rf voltages were about 65% of that observed for a conventional tuned substrate (180° phase) at equal input power density and frequency. A manually loaded version used a 150 mm diam SiO2 target and a load-locked version used a 178 mm diam target for better uniformity. SiO2 films have been deposited at rates as high as 4300 Å/min in a low-resputtering mode. In a planarizing mode, rates of 1750 Å/min were observed. Resputtering could be smoothly adjusted from near zero to at least as high as 70%. Temperature was controlled by gas conduction cooling to temperatures below 400 °C. Film stress decreased with deposition rate at constant resputtering and increased with resputtering. Uniformity and other film properties were measured. © 1990, American Vacuum Society. All rights reserved.