Jean-Christophe Imbert

Experimental study of a pre-ionized high power pulsed magnetron discharge

This paper is focused on experimental studies of a high power pulsed magnetron discharge stabilized by low current pre-ionization. Time resolved studies were performed for a Cu target by optical emission spectroscopy and electrical measurements for different pressures of Ar buffer gas. Due to the elimination of the statistical delay time and a fast discharge current rise the quasi-stationary state was reached in 6 µs. The quasi-stationary state is characterized by an extremely high and pressure independent discharge current density of ~10 A cm−2 and stable Cu+ and Cu++ emissions. Such fast discharge dynamics permits the magnetron cathode current to be driven with a pulse of duration of the order of a few µs, significantly shorter than in other devices. During this short time, the plasma does not have time to undergo the transition from the glow to the arc discharge even at the extremely high cathode loads met in our case. Different stages of the fast discharge development are identified and the composition of the magnetized plasma as a function of the pressure is discussed in detail.

Study of the transport of titanium neutrals and ions in the post-discharge of a high power pulsed magnetron sputtering device

This paper deals with the diagnostics of a high power pulsed magnetron sputtering device (HPPMS). The HPPMS plasma was spatially and temporally characterized in the post-discharge using optical absorption spectroscopy and Langmuir probe time resolved measurements. A circular titanium target was used, the buffer gas was argon and the pressure was fixed at 4 Pa. The titanium densities (neutrals and ions) were measured by a pulsed resonant absorption spectroscopy technique. We found an ionization degree higher than 0.5. Comparison beetween the experimental results and a simple one-dimensional model of diffusion shows that in these conditions, the transport of neutral and ionized sputtered atoms is mainly controlled by diffusion (ambipolar diffusion for ions).

Spatial characterization of an IPVD reactor : neutral gas temperature and interpretation of optical spectroscopy measurements

This paper deals with the characterization of an ionized physical vapour deposition (IPVD) reactor using an additional microwave plasma. The IPVD reactor was spatially characterized using optical emission spectroscopy, optical absorption spectroscopy and Langmuir probe measurements. A rectangular titanium target was used, the buffer gas was argon and the pressure was fixed at 4 Pa. The influence of the microwave power (between 0 and 900 W) and the magnetron discharge current (0.5 and 2 A) on the densities of the titanium species (neutral and ionic), argon emission line intensity and titanium and argon temperature variations was investigated. The titanium temperature and densities were measured using the pulsed resonant absorption spectroscopy technique. The neutral and ion fluxes on the substrate were deduced from these measurements. It was found that the ratio (Ti+)/(Tin) increases by a factor of 30 when additional microwave plasma is used. Moreover, we point out the temperature as a key parameter in plasma diagnostic interpretations.

Recent Developments on Ionized Physical Vapour Deposition: Concepts, Determination of the Ionisation Efficiency and Improvement of Deposited Films

While most of the IPVD reactors use radio-frequency (RF) coils to create additional ionization, we developed an alternative technique consisting of a home made magnetron sputtering device in which the ionization of the emitted sputtered vapor is achieved by two microwave antennas. Langmuir probe measurements were used to determine electronic density and temperature. Emission optical spectroscopy has been performed and argon and titanium line intensities have been measured, showing an increase of Ti+* to Ti* line intensity ratio. Optical absorption spectroscopy using a titanium hollow cathode lamp powered with a pulsed power supply has also been performed to determine the ionized fraction of the sputtered vapor. Preliminary results are also given for a conventional IPVD system (with RF loops) used for the deposition of Ti-based biomaterials.