Mass and Energy Resolved Detection of Ions and Neutral Sputtered Species Incident at the Substrate During Reactive Magnetron Sputtering of Ti in Mixed Ar+N 2 Mixtures

The fluxes of ions and neutral sputtered particles incident at the growth surface during the deposition of TiN by reactive magnetron sputtering from a Ti target in mixed Ar+N 2 discharges were determined using a combination of in situ double-modulation mass spectrometry, Langmuir probe, discharge, deposition rate, and film composition measurements. The N2 fraction fN2in the discharge was varied from 0 to 1 with the total pressure maintained at 3 mTorr (0.4 Pa). Target nitridation, observed directly through the detection of sputter-ejected TiN molecules, was found to occur over the narrow fN2range between =0.035 and 0.06. With fN2 0.1, more than 94% of the ion flux incident at the substrate is Ar+ while for pure N2 discharges, N+2accounts for more than 95% of the incident ions. Both the incident Ar+ and N+2ion fluxes are highly monoenergetic with energies corresponding to e Vs, where Vsis the applied negative substrate bias with respect to the plasma potential. However, the energy distributions of incident Ti+and N+ ions are extended due to the high-energy tails in their sputter-ejection energy distributions. The primary sputter-ejected particles are Ti and N atoms. TiN, TiN+, and Ti+do not contribute significantly to film growth kinetics.