Energy resolved ion mass spectroscopy of the plasma during CV reactive magnetron sputtering

The energy distribution and composition of the ion flux on a substrate duri ng reactive magnetron sputtering of TiN and TiWN films were studied by the energy resolved mass spectroscopy. The entrance flange of the probe Hiden E QP500 was positioned in a distance of 50 mm from the Ti or WTi (70:30 at.%) target 100 mm in diameter. The sputtering was carried out in a mixture of argon and nitrogen of various compositions at pressures from 0.05 to 10 Pa and discharge currents from 0.5 to 7 A. The energy spectra of ions at low p ressures were characterized by extended high-energy tails. The high energy of sputtered (metal) atoms follows from their distribution at the cathode a fter being sputtered. The high-energy gas ions (At+, N-2(+), N+) stem from two sources. One is the transfer of energy in the collisions with the sputt ered metal atoms. The other is the reflection of the energetic ions from he avy elements in the target. A strong reduction of the ion energy at the sub strate was found when the pressure was increased from 0.5 to 10 Pa. As a co nsequence of a loss of energy in many collisions the high-energy portion of the ion energy spectra diminished and the energy spectra of various kinds of ions became similar. Nevertheless, the reflected ions were still apparen t, albeit at lower intensity. The TRIM Monte-Carlo simulation showed that t he flux of the fast reflected ions and flux of sputtered atoms are of the s ame order of magnitude, indicating thus the important role of the former sp ecies in forming the film properties at low pressures. The analysis of the composition of the ion flux during sputtering in a mixture of nitrogen and argon revealed that the ratio of ion fluxes TiN+/Ti+ reached maximum of app roximately 0.13, while WN+/W+ was up to 0.3. (C) 2001 Elsevier Science B.V. All rights reserved.