Time resolved metal line profile by near-ultraviolet tunable diode laser absorption spectroscopy

International audienc

On Both Spatial And Velocity Distribution Of Sputtered Particles In Magnetron Discharge

The kinetics of the sputtered atoms from the metallic target as well as the time-space distribution of the argon metastable atoms have been investigated for DC and high power pulse magnetron discharge by means of Tunable Diode – Laser Absorption Spectroscopy (TD-LAS) and Tunable Diode – Laser Induced Fluorescence (TD-LIF). The discharge was operated in argon (5-30 mTorr) with two different targets, tungsten and aluminum, for pulses of 1 to 20 μs, at frequencies of 0.2 to 1 kHz. Peak current intensity of ~100 A has been attained at cathode peak voltage of ~1 kV. The mean velocity distribution functions and particle fluxes of the sputtered metal atoms, in parallel and perpendicular direction to the target, have been obtained and compared for DC and pulse mode

Space-resolved velocity and flux distributions of sputtered Ti atoms in a planar circular magnetron discharge

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Argon metastables in HiPIMS: validation of the ionization region model by direct comparison to time resolved tunable diode-laser diagnostics

International audienceThe volume plasma interactions of high power impulse magnetron sputtering (HiPIMS) discharges operated with a Ti target is analyzed in detail by combining time-resolved diagnostics with modeling of plasma kinetics. The model employed is the ionization region model (IRM) with an improved and detailed treatment of the kinetics of the argon metastable (Arm) state, called m-IRM. The diagnostics used is tunable diode-laser absorption spectroscopy (TD-LAS) of the Arm state, which gives the line-of-sight density integrated along the laser path parallel to the target surface. The TD-LAS recordings exhibit quite complex temporal evolutions Arm(t), with distinct features that are shown to reflect the time evolution of the plasma (the electron density and temperature), and of the argon gas (gas rarefaction and refill). The Arm(t) function is thus a tracer for the most important aspects of internal discharge physics, and therefore suitable for model testing and validation. The IRM model is constructed to be locked to obey specific experimental macroscopic discharge parameters, specifically the discharge current ID(t) and the voltage UD(t). It has to this purpose been run with the appropriate process gas pressures (from 0.67 to 2.67 Pa), with the experimentally applied voltage pulse profiles UD(t), and with the resulting current pulse profiles ID(t) (with maxima from 0.5 to 70 A). It is shown that the model reproduces the features in the TD-LAS measurements: both the Arm(t) evolution in single pulses, and how the pulse shapes change with gas pressure and with pulse amplitude. The good agreement between the measurements and model output is in this work taken to validate the basic assumptions of the m-IRM. In addition, the m-IRM results have been used to unravel the connections between volume plasma kinetics and various features recorded in the TD-LAS measurement, and to generalize the foremost characteristics of the studied discharges

On the anisotropy and thermalization of the metal sputtered atoms in a low-pressure magnetron discharge

Space-resolved velocity distributions of titanium atoms sputtered in a direct-current (dc) magnetron discharge working at low pressure (0.4 Pa) were investigated using the laser-diode–induced fluorescence technique. A blue-light laser diode, covering the Ti $3d^{2}4s^{2}$-$3d^{2}(^{3}F)4s4p(^{1}P^{0})$ transition $\lambda_{0}$=398.289 nm, was used to excite neutral Ti atoms and to measure their Doppler absorption profile through the induced fluorescence signal. Taking advantage of the very narrow laser linewidth, energetic and thermalized atoms can be clearly distinguished. Moreover, flux distributions of sputtered atoms along the laser direction were deduced and discussed