N. Britun

Determination of the vibrational, rotational and electron temperatures in N2 and Ar–N2 rf discharge

In order to characterize a nonequilibrium molecular plasma from the point of view of translational, vibrational and rotational degrees of freedom and their interaction, the characteristic temperatures of such a plasma were measured in an ICP rf reactor. Both pure nitrogen and argon–nitrogen mixture plasmas were examined for this purpose.The experimental results of rotational (Tr), vibrational (Tv) and electron (Te) temperatures are presented. Vibrational and rotational temperatures were measured as a function of nitrogen content for both E and H modes of ICP discharge using a power range of 45–200 W and pressure range of 2.6–13.3 Pa. Additionally, the pressure dependence of electron temperature in a pure nitrogen discharge was studied. Results show that rotational temperature is ≈370 K for E mode and ≈470 K for H mode and almost does not depend on either the applied rf power or the nitrogen content in the discharge. Vibrational temperature groups in the range 5000–12 000 K increase with applied rf power and constantly decay with an increase of nitrogen content. The measured values and behaviour of electron temperature are comparable with those for the positive column of the dc glow discharge. The results also prove that these three temperatures obey the classical inequality Te > Tv > Tr, as well as clarifying the differences in both vibrational and rotational temperature for different modes of the ICP discharge.

Velocity distribution of neutral species during magnetron sputtering by Fabry–Perot interferometry

The velocity distribution of a metallic neutral species sputtered in a dc magnetron discharge was measured using a planar Fabry–Perot interferometer and a hollow cathode lamp as a reference source. The measurement was performed under different angles of view relative to the target surface. The velocity distribution function in the direction perpendicular to the target becomes asymmetrical as the Ar pressure decreases, whereas it remains nearly symmetrical when the line of sight is parallel to the target surface. The average velocity of the sputtered Ti atoms was measured to be about 2km∕s.

Titanium density analysed by optical absorption and emission spectroscopy in a dc magnetron discharge

This paper presents an optical diagnostic examination of dc planar magnetron discharge used for titanium deposition at 30 mTorr in argon bulk gas. The results were obtained by optical absorption (OAS) and emission (OES) spectroscopy for two distances from the target without substrate. The absolute density of titanium in the ground and metastable states at 4 cm from the target ranged, respectively, between 8 × 1010 cm−3 and 1012 cm−3 and between 6 × 1010 cm−3 and 3 × 1011 cm−3, in the range 0.2–1.0 A. OES results were used to prepare an assumed interpretation in terms of differences in loss mechanisms, mainly by either diffusion towards the walls for all particles at 8 cm from the target or collision losses for non-radiative species at 4 cm from the target, except for the titanium ground state. This was confirmed by our results of the argon metastable density measurement at 4 cm which was constant at around 7 × 1010 cm−3 with discharge current.

Fabry–Perot interferometry for measurements of the velocity of sputtered atoms in a magnetron discharge

A planar Fabry?Perot interferometer was utilized to measure the velocity distribution function (vdf) of the atoms sputtered in a dc magnetron discharge. The measurements were performed during the sputtering of several metal targets under different discharge conditions such as applied power, working pressure and the distance from the magnetron target. The results demonstrate that there is a considerable shift of the vdf depending on the working pressure and the atomic weight of the sputtered atoms when the line of sight is perpendicular to the target. At the same time the velocity corresponding to the maximum of the vdf does not vary appreciably with the applied power. The typical net velocity of the sputtering atoms was found to be about 2?km?s?1, which is in good agreement with the data obtained recently by other diagnostic methods.

Laser induced fluorescence for Ti and Ti+ density characterization in a magnetron discharge

Laser induced fluorescence (LIF) was utilized for the determination of the densities of Ti atoms and ions (Ti+) in a dc magnetron discharge. The densities were measured under different discharge conditions, namely the discharge current, working pressure and distance from the magnetron target. The total density of species in the discharge was calculated using additional measurements of the broadening of the absorption lines for both Ti and Ti+. The width of the absorption lines appears to be different for the neutrals and ions. To obtain the absolute values of the density measured by LIF, absorption spectroscopy measurements were used. As a result of calibration of the LIF data by the optical absorption spectroscopy the absolute value of the density of Ti atoms was found to be ~2 × 1011 cm−3 near the magnetron target at about 6 mTorr. Similar results were obtained for Ti+ ions with a maximum value of the absolute density of ~3 × 109 cm−3.

Experimental study of Ar and Ar–N2 afterglow in a pulse-modulated ICP discharge: observation of highly excited Ar(6d) afterpeak emission

In an argon ICP RF discharge modulated by 1?kHz square pulses, strong emission at 549.6?nm (corresponding to the upper level Ar(6d)) was observed about 100??s after the pulse termination in the afterglow. This emission exceeds by a factor of as much as five the duty-on cycle intensity. With simple kinetic considerations, we assigned this emission to the Penning pooling ionization of argon metastable atoms leading to the formation of in the afterglow followed by electron?ion recombination producing highly excited argon atoms Ar(6d). With the addition of 1% N2 into Ar, the emission at 549.6?nm completely disappeared in the afterglow. This disappearance could be explained by excitation transfer between Ar metastable atoms and nitrogen molecules leading to the emission of the second positive system of N2..

Anomalously high surface temperature induced by condensation of atoms

The effect of extremely high temperatures developing on the surface during the condensation of sputtered atoms has been discovered for the first time by direct surface temperature measurements. This temperature is considerably higher than the temperature of the solid film beneath and proportional to the flux of atoms impinging on the surface. The surface temperature steeply grows as the condensation starts, exists during the period of condensation, and rapidly decays after its termination. The effect is related to the anomalously low thermal conductivity of the superficial layer that is formed by highly mobile atoms arriving on the condensation surface. This superficial layer can be viewed as a new state of matter characterized by its anomalously low thermal conductivity.