Mechanistic Considerations in Plasma-Assisted Etching of Ag and Au Thin Films

Abstract

Low temperature plasma-based subtractive etching of Ag and Au films was demonstrated and results compared to those of similar studies for Cu etching. Ag and Au were etched in H2 plasmas at 10°C at rates of 33 nm/min and 26 nm/min, respectively. These rates were higher than those reported for Cu etching in H2 plasmas. Such results suggest that metal reaction with hydrogen to form hydrides plays an important role in the plasma etch process for these Group 11 metals. Unlike Cu, etch rates of Ag and Au increased with an increase in etchant species (He and Ar) atomic mass. Comparison of Ag etch rates using H2, He, and Ar plasmas with those of Cu indicates that momentum transfer during the etch process plays a more significant role in Ag etching than in Cu etching. In addition, the higher etch rate of Au relative to Cu in an H2 plasma, indicates the importance of chemical reaction between H2 and Au in the Au etching mechanism.