Papers

ICMCTF2006 Session B10: PVD Process Modeling

Wednesday, May 3, 2006 10:30 AM in Room Golden West

Wednesday Morning

Start	Invited?	Item
10:30 AM		B10-7 Heuristic and Atomistic Simulation of Reactive Magnetron Sputtering A. Pflug, M. Siemers, B. Szyszka (Fraunhofer IST, Germany); D. Severin, M. Wuttig (I. Physikalisches Institut, Germany); T. Nyberg, O. Kappertz (Uppsala University, Sweden); C. Berger (Darmstadt University of Technology, Germany) An improved theoretical understanding of the reactive magnetron sputtering process is essential for the future advancement of this technology especially with respect to model based process control and achievement of high-precision film homogeneity. The most important aspects of reactive sputtering are the plasma physics and the emission characteristics of the sputtering target for electrons, ions and sputtered neutrals. These quantities determine the plasma impedance, which in turn determines the whole process kinetics in terms of ion current, target erosion rate as well as the reactive gas consumption. This work introduces a heuristic model for the plasma impedance and for the target emission characteristics based on a two-layer model allowing for surface chemisorption and ion implantation mechanisms. In parallel an implementation of a particle-in-cell (PICMC) plasma simulation of a magnetron discharge with self-consistent electric field is presented. It is demonstrated how the PICMC simulation is used in order to eliminate formerly unknown parameters of the plasma impedance within the heuristic model. As shown by parameter sets for various materials such as Hf, W, Ti, the new heuristic model is the first which can quantitatively reproduce sets of voltage and deposition rate hysteresis curves obtained from reactive DC sputtering in a lab coater for various constant current set points. The non-linear kinetic properties of the new heuristic model and the implications for advanced process control of reactive sputtering are discussed.}
11:10 AM		B10-9 Reactive Magnetron Sputtering : the Effect of Ion Implantation D.J. Depla, R. De Gryse (University Ghent, Belgium) During reactive ion bombardment compound is formed in the target subsurface region and the formation rate is influenced by the sputtering of the target. By changing the angle of incidence between the reactive ion beam and the surface, the sputter yield is modified, and its influence on the compound formation can be studied. Typically, compound is formed at normal incidence and at small impact angles but above a critical angle no complete target oxidation is noticed. This can be understood as follows. The average sputter yield of the target increases with an increasing angle, resulting in a lower concentration of the implanted ions, as the steady-state concentration of implanted reactive ions is, in first order, inversely proportional with the sputter yield. In this way the reduction of the sputter yield by the compound formation is compensated by increasing the sputter yield at higher impact angles, which reduces the target oxidation. Such a change from a partial oxidized target to a complete oxidized target under influence of reactive ion bombardment has been recently reported during reactive magnetron sputtering, where the target is bombarded at normal incidence by a mixture of low energy reactive and argon ions. Similar, to the ion beam experiments, the compound formation reduces the average sputter yield of the target. So with increasing reactive gas mole fraction, more reactive ions become implanted while, due to the compound formation, less target material is removed from the target. This can result in an abrupt change of the target condition. Although the experimental conditions of both techniques differ strongly, the oxidation mechanism is similar. In this paper both type of experiments are described with the same analytical model. During reactive magnetron sputtering the oxidation of the target is also influenced by chemisorption. This latter effect is also studied using the same analytical model.
11:30 AM		B10-10 Linearized Model Analysis and LQR-Based Stabilizing Controller Design for Reactive Sputtering Processes D.J. Christie (Advanced Energy Industries, Inc.) Reactive sputtering processes exhibit unique control space behavior which has been effectively explained by mathematical models. The reactive gas partial pressure can have multiple possible values for a range of reactive gas flows which leads to hysteresis in the process control space. A model which effectively explains the process dynamics consists of three coupled non-linear differential equations. Jacobian linearization of the model equations can be used to create a linearized model whose eigenvalues can be determined explicitly¹. Then, the multi-variable linear quadratic regulator (LQR) technique can be used to find a starting point for stabilizing controller design. Root locus techniques can then be used to design a controller with the desired stability margin at a given operating point. This approach has been studied numerically for industrially relevant processes. Results for a system representative of commercial large area transition mode reactive sputtering processes are presented. ¹C. Li, J-H Hsieh, Surface and Coatings Technology 177-178, 824 (2004).