Michael Siemers

Process stabilization and increase of the deposition rate in reactive sputtering of metal oxides and oxynitrides

Reactive sputtering processes normally exhibit undesirable hysteresis effects which are more pronounced for oxide than nitride deposition. We present a method to reduce and ultimately eliminate these effects for reactive sputtering of metal oxides and oxynitrides. This is achieved by the addition of nitrogen to the oxygen process, which in addition leads to a higher deposition rate. These observations can be qualitatively explained and theoretically predicted using an extension of the Bergs model to two different reactive gases. Although the nitrogen addition leads to pronounced changes of the processing characteristics, incorporation of nitrogen into the growing film is very small.

Parallel DSMC gasflow simulation of an in-line coater for reactive sputtering

There is an increasing demand for high precision coatings on large areas via in-line reactive sputtering, which requires advanced process control techniques. Thus, an improved theoretical understanding of the reactive sputtering process kinetics is mandatory for further technical improvement. We present a detailed Direct Simulation Monte Carlo (DSMC) gas flow model of an in-line sputtering coater for large area architectural glazing. With this model, the pressure fluctuations caused by a moving substrate are calculated in comparison with the experiment. The model reveals a significant phase shift in the pressure fluctuations between the areas above the center and the edges of the substrate. This is a geometric effect and is e. g. independent of the substrate travelling direction. Consequently, a long sputtering source will observe pressure fluctuations at its center and edges, which are out of phase. For a heuristic model of the reactive sputtering process, we show that in certain cases a two-dimensional model treatment is sufficient for predicting the film thickness distribution on the moving substrate. In other cases, a strong phase shift between averaged pressure fluctuations and reactive sputtering process response is observed indicating that a threedimensional model treatment is required for a realistic simulation of the in-line deposition process.

Sputter yield amplification by tungsten doping of Al2O3 employing reactive serial co-sputtering: process characteristics and resulting film properties

The deposition rate of reactively sputtered Al2O3 coatings is demonstrated to increase by 80% upon tungsten doping of the used aluminium target. This effect is based on the recoil of the sputtering species at implanted dopants below the target surface and is termed sputter yield amplification. For the investigation of this effect, a novel type of magnetron sputter deposition system is employed that facilitates serial co-sputtering. In this technique doping of the elementary target is enabled by a dynamic sputtering process from an auxiliary cathode. In our case, the rotating aluminium target is dynamically coated with tungsten from this auxiliary cathode. Since the primary target rotates, the auxiliary cathode is placed in series with the primary erosion zone. The deposition rate of Al2O3 can be considerably increased in this process already for very low concentrations of approximately 1% of tungsten in the resulting film. A characterization of the dynamics of reactive sputtering as a function of target rotation speed is performed.

Parallel particle-in-cell monte-carlo algorithm for simulation of gas discharges under PVM and MPI

The simulation of complex problems in the field of plasma deposition technology requires the usage of parallel code running on modern multicore architectures. The inhouse developed Particle-in-Cell Monte-Carlo (PIC-MC) simulation environment has recently been ported from PVM towards MPI, which is the de-facto standard for parallelization by message passing. We measured a shorter latency time of MPI in comparison with PVM and determined the impact on the PIC-MC performance.