Sputtering
Sputtering, like evaporation, is performated in a vacuum chamber. The source material and the substrate (wafer) and placed on opposing parallel plates connected to a high-voltage power supply as pictured in Fig.4.13. During a deposition the chamber is fist evacuated
Figure4.13 schematic of a d.c. sputtering system. The source material covers the cathode while the wafer is mounted on the system anode. (From Jaeger 1988 by Addison-wesley Publishing Co., Inc. Reprinted by permission of the publisher.) of air and then a low-pressure amount of sputtering gas, typically Ar, is admitted in to the chamber. Applying an interelectrode voltage ionizes the Ar gas and creates a plasma between the plates. Since the plate covered with source material is maintained at the necative potential relative to the substrate, Ar* irons accelerated toward and into the source covered plate. The impacting Ar* irons are in turn cause source atoms or moreculas to be ejected from this plate. Being neutral, the ejected atoms or molecules readily traval to the substrate where they deposit to from the desired thin firm. A d.c. power supply can be used when depositing metals, and an RF supply is necessary to in traduce a gas of one of the components to assure the formation of a near- stoichiometric film. Providing low-temperature , low-contamination film with and acceptable throuthput , sputtering has become the chief commercial methord of depositing Al and other metals.