Ionization of sputtered material in a planar magnetron discharge

Abstract

Emission spectra in the visible and near ultraviolet have been recorded for the magnetron sputtering of titanium by argon at pressures between 0.5 and 100 Pa. Intense emission lines from both atomic and ionic material were detected, and comparison of line intensities yielded an ionization fraction of over 10% and an electron temperature of the order of 1 eV for the sputtered material. The ionization fraction decreased with increasing magnetron power, and an optimal operating pressure was found for maximum ion content of the sputtered flux. Scaling laws of emission line intensity with magnetron power indicated the incomplete thermalization of sputtered metal with the sputtering plasma, and spatially resolved measurements of ionization profiles were used to investigate the transport and collisional ionization of sputtered material. Penning ionization of sputtered titanium by metastable argon was found to be the dominant ionization process, and the effect of diffusion of metastable argon was noted. Control of ion content in sputtered fluxes is of interest for the deposition of thin films and for metallization of semiconductors.

An introduction to thin film processing using high-power impulse magnetron sputtering

“…14 Typical example is a CrN/NbN film deposited on steel substrates etched using HiPIMS (pretreatment by Nb + ions at a substrate bias voltage of À1000 V) exhibited a scratch test critical load (L c ) of 56 N, which was higher than the values of 25 N obtained for films deposited on substrates etched by a DCMS plasma (substrate bias voltage of À1000 V at an Ar pressure of 0.8 Pa), 14 which exhibit a significantly lower ionization degree for both Ar + and metal ions. 19 It should also be pointed out here that the L c values achieved on HiPIMS etched substrates are comparable to those for films grown on substrates cleaned using high fluxes of Ar + ions generated by an external ionization source. 126 This fact indicates that HiPIMS can be used as an alternative process to improve the quality of the filmsubstrate interface and enhance the film adhesion, when no external source for increasing the Ar ionization is available.…”

“…[19][20][21] When the deposition flux consists of more ions than neutrals, the process is referred to as ionized PVD or IPVD. 5 There are a few different IPVD techniques available today, such as postvaporization ionization using a secondary plasma generated by, for example, an RF coil placed in the deposition chamber to create ions that can be accelerated to the substrate surface when applying a negative bias.…”

“…12,92 This is in contrast to the growth by DCMS, where the majority of the ions in the deposition flux consists of the much lighter Ar + ions. 19 HiPIMS thus provides tools for better influencing the internal stresses of the growing Ta films and accordingly the possibility to deposit a-Ta films at room temperature (Fig. 7).…”

Exploring the potential of high power impulse magnetron sputtering for growth of diamond-like carbon films

“…dcMS) [18,19]. The high values of peak target power density result in generation of plasmas with densities between 10 17 and 10 19 m -3 [20] much higher than the typical values observed in dcMS plasmas in the range 10 14 to 10 16 m -3 [15]. The high plasma densities, in turn, have as a consequence high degrees of ionization of both gas and sputtered species (peak values up to 90% for Ti [21]) and peak substrate ion current densities up to three orders of magnitude higher than those obtained in dcMS processes [17].…”

“…On the other hand, magnetron sputtering (MS) based techniques are widely employed in industrial processes due to their conceptual simplicity and their ability to deposit uniform films with relatively high rates. However, magnetron sputtering plasmas (in dc, pulsed and rf configuration) are characterized by relatively low electron densities (in the order of 10 15 m -3 ) and low degrees of ionization (in the order of a few %) of both gas and sputtered species [15]. This, in the case of amorphous carbon films, has been shown to lead to the growth of films with sp 3 bond fractions significantly lower than those achieved by FCA and PLD, e.g.…”