Wouter Leroy

Modeling the flux of high energy negative ions during reactive magnetron sputtering

The negative ion flux during reactive sputtering from planar and rotating cylindrical magnetrons has been studied. Energy resolved mass spectrometry was used to measure the energy and mass distribution of the negative ions. Also the angular distribution of the high energy ions was characterized for planar as well as for rotating cylindrical magnetrons. Besides these measurements, a binary collision Monte Carlo simulation code, SiMTRA, was adapted in order to simulate the energy, mass, and angular distribution of the high energy negative ions. All simulated distributions, for both planar and rotating cylindrical magnetrons, were in excellent correspondence with the experimental observations. Also a model for the amount of high energy negative O− ions was proposed. Indeed, the logarithm of the amount of high energy negative O− ions is shown to be related to the secondary electron emission yield of the oxide target, and these two parameters are known to be related to the work function. The SiMTRA simulations...

Angular-resolved energy flux measurements of a dc- and HIPIMS-powered rotating cylindrical magnetron in reactive and non-reactive atmosphere

A rotating cylindrical magnetron equipped with a titanium target was sputtered in dc and in HIPIMS mode, both in metallic and in the oxide regime. For all sputter modes, the same process conditions and the same average sputtering power of 300 W were used. An angular-resolved study was performed, 90° around the rotating cylindrical magnetron, which obtained the total energy flux arriving at the substrate. Furthermore, the energy flux per adparticle was calculated by measuring the deposition rate for all sputter modes and regimes. There is only a small difference in total arriving energy flux between the dc mode and the HIPIMS mode. A maximum arriving energy flux of ca 0.26 mW cm−2 was measured, when normalized to the sputtering power. Concerning the deposition rate, up to a 75% decrease was found from dc to HIPIMS mode. Furthermore, the emission and the transport of the particles have a similar angular profile for all sputter modes. Among the HIPIMS modes, a decrease in deposition rate was measured with increasing pulse length. Therefore, the energy which arrives per adparticle is the highest for the HIPIMS modes. A difference in the angular shape of the energy per arriving adparticle is noticed between the dc and the HIPIMS modes. The dc mode has a maximum arriving energy per adparticle at around 50°, while this is at 60° for the HIPIMS mode.

Influence of particle and energy flux on stress and texture development in magnetron sputtered TiN films

The real-time stress evolution during reactive dc magnetron sputter deposition of TiN films in Ar+N2 plasma discharge was measured in situ using a multiple-beam optical stress sensor, while the film texture was determined ex situ using x-ray diffraction. The influence of atomic N/Ti flux and energy flux, previously quantified by combining plasma characterization and Monte Carlo simulations (2009 J. Phys. D: Appl. Phys. 42 053002), was investigated by varying either the N2 partial pressure at fixed total pressure, the total working pressure or the bias voltage applied to the substrate. The contribution of thermal stress was carefully taken into account from thermal probe measurements to evaluate the intrinsic (growth) stress from the measured film force data. A clear correlation between stress, film texture and energy flux is evidenced: while underdense (1?1?1)-textured TiN films with ?V?-shaped columnar growth (zone T) are under tensile stress (up to +0.6?GPa), dense TiN films with zone II microstructure develop a (0?0?2) texture and large compressive stress (up to 3?GPa) when the energy flux is higher than ?150?eV per incoming particle. However, it is shown that a positive or negative bias voltage, though increasing the energy flux, did not promote a (0?0?2) texture. It is concluded that compressive stress development and (0?0?2) preferential growth are both kinetically driven processes in magnetron sputtered TiN layers, but exhibit distinct dependence with the substrate fluxes.

Rotating cylindrical magnetron sputtering: Simulation of the reactive process

A rotating cylindrical magnetron consists of a cylindrical tube, functioning as the cathode, which rotates around a stationary magnet assembly. In stationary mode, the cylindrical magnetron behaves similar to a planar magnetron with respect to the influence of reactive gas addition to the plasma. However, the transition from metallic mode to poisoned mode and vice versa depends on the rotation speed. An existing model has been modified to simulate the influence of target rotation on the well known hysteresis behavior during reactive magnetron sputtering. The model shows that the existing poisoning mechanisms, i.e., chemisorption, direct reactive ion implantation and knock on implantation, are insufficient to describe the poisoning behavior of the rotating target. A better description of the process is only possible by including the deposition of sputtered material on the target.

Influence of deposition on the reactive sputter behaviour during rotating cylindrical magnetron sputtering

A key feature of a rotating cylindrical magnetron is the changing race track position due to target rotation. To study the reactive magnetron sputtering of aluminium for this magnetron type, so-called sputter cleaning experiments were designed. In these experiments, the target was first sputtered without rotating the target. After this treatment, the target was sputter cleaned in pure argon while rotating the target. In the meantime, the discharge voltage was recorded as a function of time. The obtained results can be understood by including compound deposition on the target as an extra mechanism for target poisoning.

Smart textiles: an explorative study of the use of magnetron sputter deposition

Reactive magnetron sputtering is a widely used deposition technique in different application areas. In this study its use is evaluated for the deposition of metal thin films (Al, Cu and Ti) and oxide thin films (Al2O3, TiOx) on woven and nonwoven substrates. The study shows that good adhesion can only be achieved when the substrate is pre-treated in a glow discharge. The influence of the substrate on the reflectivity of Al and Cu thin films was investigated. For conductive textile applications, the resistivity of metal thin films and TiOx was investigated.

Experimental determination and simulation of the angular distribution of the metal flux during magnetron sputter deposition

To understand the film growth during magnetron sputter deposition a detailed knowledge of the flux of sputtered species from the target towards the substrate is vital. One important parameter is the angular distribution of the impinging neutral target atoms on the substrate, since it is responsible for, for example, self-shadowing effects. The determination of the angular distribution of the metal flux at an arbitrary point in the deposition chamber is achieved by a pinhole camera, where the information of the angular distribution is converted into a thickness profile. This paper describes the construction of such a pinhole camera which is capable of differential pumping, the determination of the angular distribution for a wide variety of target materials, and which can easily be inserted into a deposition chamber. The angular distributions of different materials (Cu, W, Al, Ti, Mg) at different parameters (pressure, lateral position and vertical position) are experimentally determined and compared with simulations obtained from a newly developed Monte Carlo code. It was also investigated whether parameters derived from the angular distribution are related to the degree of thermalization of the impinging particles.

Noble gas retention in the target during rotating cylindrical magnetron sputtering

A rotating cylindrical magnetron with a Ti target was sputtered in pure Xe or in a mixture of Xe and N2. The atomic composition of the target surface during sputtering has been investigated by in situ Rutherford backscattering spectrometry. The noble gas atomic ratio at the target surface is around 3.4% or 9.8% for sputtering in pure Xe and with 10% N2 addition, respectively. Energy resolved mass spectrometry reveals that some of the implanted Xe atoms are sputtered from the target. A radiation enhanced diffusion/detrapping/sputtering mechanism is proposed to model the flux of noble gas leaving the target during sputtering.

High power impulse magnetron sputtering using a rotating cylindrical magnetron

Both the industrially favorable deposition technique, high power impulse magnetron sputtering (HIPIMS), and the industrially popular rotating cylindrical magnetron have been successfully combined. A stable operation without arcing, leaks, or other complications for the rotatable magnetron was attained, with current densities around 11 A cm−2. For Ti and Al, a much higher degree in ionization in the plasma region was observed for the HIPIMS mode compared to the direct current mode.Both the industrially favorable deposition technique, high power impulse magnetron sputtering (HIPIMS), and the industrially popular rotating cylindrical magnetron have been successfully combined. A stable operation without arcing, leaks, or other complications for the rotatable magnetron was attained, with current densities around 11 A cm−2. For Ti and Al, a much higher degree in ionization in the plasma region was observed for the HIPIMS mode compared to the direct current mode.

Momentum transfer driven textural changes of CeO2 thin films

The influence of the target erosion depth on the film texture was investigated during DC reactive magnetron sputter deposition of CeO2 thin films. Three fluxes towards the substrate surface (the relative negative oxygen ion flux, the material flux, and the energy flux) were measured and related to the ongoing erosion of a cerium target. As the deposition rate increased for more eroded targets, both the energy flux and the negative ion flux decreased. Cerium oxide thin films that were deposited at different target erosion states, exhibited a change in preferential crystalline orientation from [200] to [111]. This textural change cannot be explained in terms of the energy per arriving atom concept. Instead, it is shown that the momentum of the high energetic negative ions is an essential condition to clarify the witnessed trends.