Origin and Effects of Negative Ions in the Sputtering of Intermetallic Compounds

An unexpected etching phenomenon during the sputtering of rare earth-gold alloys has been found to be caused by a large flux of negative gold ions from the sputtering target. We find this effect to occur in a range of intermetallic compounds. A model is presented which predicts when negative ion formation will be important. Effects of negative ions on sputter deposition of thin films include reduced deposition rate or substrate etching, and changes in film composition and other properties. Negative ion formation must also be taken into account for accurate quantitative analysis by Secondary Ion Mass Spectrometry (SIMS).