HIPIMS (High Power Impulse Magnetron Sputtering) discharge is a new PVD technology for the deposition of high-quality thin films. The deposition flux contains a high degree of metal ionization and nitrogen dissociation. The microstructure of HIPIMS-deposited nitride films is denser compared to conventional sputter technologies. However, the mechanisms acting on the microstructure, texture and properties have not been discussed in detail so far. In this study, the growth of TiN by HIPIMS of Ti in mixed Ar and N2 atmosphere has been investigated. Varying degrees of metal ionization and nitrogen dissociation were produced by increasing the peak discharge current (Id) from 5 to 30 A. The average power was maintained constant by adjusting the frequency. Mass spectrometry measurements of the deposition flux revealed a high content of ionized film-forming species, such as Ti1+, Ti2+ and atomic nitrogen N1+. Ti1+ ions with energies up to 50 eV were detected during the pulse with reducing energy in the pulse-off times. Langmuir probe measurements showed that the peak plasma density during the pulse was 3 × 1016 m−3. Plasma density, and ion flux ratios of N1+: N21+ and Ti1+: Ti0 increased linearly with peak current. The ratios exceeded 1 at 30 A. TiN films deposited by HIPIMS were analyzed by X-ray diffraction, and transmission electron microscopy. At high Id, N1+: N21+ > 1 and Ti1+: Ti0 > 1 were produced; a strong 002 texture was present and column boundaries in the films were atomically tight. As Id reduced and N1+: N21+ and Ti1+: Ti0 dropped below 1, the film texture switched to strong 111 with a dense structure. At very low Id, porosity between columns developed. The effects of the significant activation of the deposition flux observed in the HIPIMS discharge on the film texture, microstructure, morphology and properties are discussed.

Using a cylindrical Langmuir probe, time-resolved measurements of plasma parameters near the substrate were carried out in a high power impulse magnetron sputtering (HIPIMS) discharge. Two different target materials (Ti and Cr) were used and a magnetron was operated at a pressure of 0.28 and 2.66 Pa, frequency of 100 Hz, pulse duration of 70 µs and a duty cycle of 0.7%.The results show that a high density plasma (n ∼ (0.1–0.8) × 1018 m−3) is generated near the substrate in the studied pressure range. A strong dependence of the plasma density on the target material is observed at the same value of the discharge current. This phenomenon is thought to be due to the effect of the sputtering yield of the target material on the ionization and transport processes in the discharge. The plasma dynamic is studied through the temporal evolution of the electron energy distribution function.

The temporal evolution of the plasma potential, V p , in a pulsed dc magnetron plasma has been determined using the emissive probe technique. The discharge was operated in the 'asymmetric bi-polar' mode, in which the discharge voltage changes polarity during part of the pulse cycle. The probe measurements, with a time-resolution of 20 ns or better, were made along a line above the racetrack, normal to the plane of the cathode target, for a fixed frequency (100 kHz), duty cycle (50%), argon pressure (0.74 Pa) and discharge power (583 W). At all the measured positions, V p was found to respond to the large and rapid changes in the cathode voltage, V d , during the different phases of the pulse cycle, with V p always more positive than V d . At a typical substrate position (>80 mm from the target), V p remains a few volts above the most positive surface in the discharge at all times. In the 'on' phase of the pulse, the measurements show a significant axial electric field is generated in the plasma, with the plasma potential dropping by a total of about 30 V over a distance of 70 mm, from the bulk plasma to a position close to the beginning of the cathode fall. This is consistent with measurements made in the dc magnetron. During the stable 'reverse' phase of the discharge, for distances greater than 18 mm from the target, the axial electric field is found to collapse, with V p elevated uniformly to about 3 V above V d . Between the target and this field-free region an ion sheath forms, and the current flowing to the target is still an ion current in this 'reverse' period. During the initial 200 ns of the voltage 'overshoot' phase (between 'on' and 'reverse' phases), V d reached a potential of +290 V; however, close to the target, V p was found to attain a much higher value, namely +378 V. Along the line of measurement, the axial electric field reverses in direction in this phase, and an electron current of up to 9 A flows to the target.The spatial and temporal measurements of V p presented here confirm a simple picture of the evolution of V p , predicted from previously made time-resolved mass spectroscopic measurements of the ionic component in the pulsed magnetron. This paper describes the development and characteristics of the emissive probe technique for such fast measurements, together with implications for the form of the measured transient potential profiles on the operation of the magnetron discharge. In particular, it addresses the charged particle drifts and the potential for sputtering of the walls and the anode by ion impact.

Plasma composition near the substrate was investigated in a high power impulse magnetron sputtering (HIPIMS) discharge using Langmuir probe analysis, mass spectroscopy, and atomic absorption spectroscopy. The HIPIMS discharge was operated in nonreactive Ar atmosphere at a pressure of 2.66 Pa and the magnetron cathode was furnished with Ti target. Plasma density, metal ion-to-neutral ratio, and gas ion-to-metal ion ratio were studied as a function of discharge current. At peak discharge current densities of similar to 1 A cm(-2), the results show that a dense plasma (n(e) similar to 10(18) m(-3)) expanded from the target toward the substrate and lasted more than 330 mu s after the supplied power was turned off. The shape of the time-averaged ion energy distribution function of sputtered material exhibited a transition from Thompson to Maxwellian distribution, indicating efficient energy transfer in the discharge. The metal content in the plasma monotonically increased with discharge current and the metal ion-to-neutral ratio reached approximately 1: 1 in the postdischarge plasma at peak current density of 5 A cm(-2). (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3000446

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