Spectrometry studies of Ag implanted silicon carbide thin films for application as a diffusion barrier against transition metals

Abstract

A diffusion kinetics study of implanted silver (Ag) ions into SiC films is conducted. SiC thin films have been processed on Si (1 0 0) substrates by electron beam deposition from a commercial high purity hot-pressed SiC sheet. The as-deposited films were thereafter implanted with Ag+ ions. Realtime Rutherford backscattering spectrometry experiments showed that Ag+ is stable until 600 °C, which is the highest temperature that the heater in the system used could achieve. Conventional RBS studies on isochronally annealed films at higher temperatures in the range between 650 °C and 950 °C reveal that there is no significant change in the spectra up to a temperature of ∼ 750 °C. At 850 °C a change in the Ag implantation profile was observed, suggesting that Ag is mobile at that temperature. The corresponding depth profile at 850 °C suggests that there is significant Ag in- diffusion, however the overall integrated intensity data indicate that most of the Ag+ is escaping out of the films. Upon annealing for one hour at 950 °C, all the Ag ions have essentially escaped out of the films and/or spread throughout the layer below the detection limit of RBS. Isothermal annealing studies over varied duration times at 850 °C confirm Ag in-diffusion, but at the same time there is evidence of depletion of Ag near-surface regions as the annealing time increases; the overall out-diffusion of the implanted metal, although steady, is found to be slow in an isothermal process. FTIR investigations point to a diffusion model through pores and grain boundaries.