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2013-07-08 - Colloque/Présentation - communication orale - Anglais - 27 page(s)

Palmucci Maria , Snyders Rony , Konstantinidis Stéphanos , "Dynamics of Short Pulses High Power Impulse Magnetron Sputtering Ti – Ar/O2 Discharges through Time- and Energy- resolved Mass Spectrometry" in 12th International Symposium on Sputtering & Plasma Processes (ISSP) , Kyoto, Japon, 2013

  • Codes CREF : Chimie des surfaces et des interfaces (DI1327), Physique des plasmas (DI1233)
  • Unités de recherche UMONS : Chimie des interactions plasma-surface (S882)
  • Instituts UMONS : Institut de Recherche en Science et Ingénierie des Matériaux (Matériaux)
  • Centres UMONS : Centre d’Innovation et de Recherche en Matériaux Polymères (CIRMAP)

Abstract(s) :

(Anglais) High Power Impulse Magnetron Sputtering (HiPIMS) technology allows tailoring films properties to a large extent thanks to the energetic ion bombardment during the film growth. Although the films synthesis has been widely studied, the plasma chemistry and the target poisoning mechanisms in reactive HiPIMS processes remain unclear in many aspects. In this work, time- and energy- resolved mass specrometry experiments were performed on discharges operated with a titanium target in argon-oxygen mixtures using a 5 mTorr working pressure. Two sets of experiments were carried out. First, the oxygen content in the gas mixture was varied between 0 and 40 %, hence the discharge evolves from the metallic to the poisoned regime. The plasma chemical composition and the time evolution of the ion energy distributions were investigated. In the second set of experiments, 18O was added to poison the target before its subsequent sputtering in Ar-16O2 mixture. 18O-based species sputtered from the poisoned target are therefore distinguished from the 16O-based species produced in the plasma bulk. For both sets of experiments, two pulse widths (5 and 20 µs) were considered; the pulse frequency was fixed at 2 kHz and the mean power kept constant (400 W) by adjusting the target voltage (Vt). As Vt increases, the amount of oxygen needed to reach the transition is reduced. Mass spectrometry scans performed on Ar+, Ti+, O+, O2+ and TiO+ ion populations reveal an increase of the oxygen-based species (O+, O2+ and TiO+) before the transition while signals related to Ti+ and Ti2+ slowly decrease. Moreover, the signal related to the TiO+ ions, which are sputtered from the oxidized target, completely disappears as Vt increases. This might be attributed to a combination of i) the reduction of the erosion rate of the oxidized target surface, ii) the dissociation of TiO+ in the plasma bulk and iii) the increased thickness of the oxide layer covering the target surface. Indeed, SRIM simulations show that O+ ions can penetrate deeper in the Ti target with increasing Vt . These features are supported by the experiments including the 18O poisoning. As Vt increases, the amount of 18O released from the target during the depoisoning process increases. Moreover, the depoisoning kinetics appears to be different in both cases: the depoisoning rate increases with Vt. This suggests a deeper oxygen implantation and therefore, a more efficient oxidation of the target although the pulse energy is identical in each experiments.