Krystof Mrozek1,2, Petr Zikan1, Adam Obrusnik1
1PlasmaSolve s.r.o., Brno, Czech Republic
2Masaryk University, Brno, Czech Republic
Uniformity of thin film coatings (both their thickness and properties) are influenced by number of factors, such as coated part geometry, type of process (arc, magnetron, PECVD, etc.) or rotation (stationary, 2-axis, 3-axis, etc.). In certain cases, the uniformity can be also affected by chamber loading. This contribution will explore the influence of different loading setups on deposition rate and coating uniformity. The investigation will be done using a solver based on the test particle Monte Carlo method. This solver can calculate relative flux of particles on the coated parts based on process type, power, pressure, substrate bias etc. on 2D or 3D geometries. This makes it a suitable tool for parametric studies without the need for time-consuming experimental work. The investigation will deal with coating of different tools in different industrial processes.
The figure below shows ion density distribution for two different carousel loadings (8 or 16 parts, visualized in a horizontal slice). The simulated process was DC magnetron sputtering in industrial coater running at 6 kW. The process used titanium cathode (length 0.6 m) in argon as operating gas (0.5 Pa). With fewer parts, the plasma sheath around each part is independent and the part gets coated at the front (facing cathode) and on the sides. With more parts the plasma sheaths at different parts start to overlap, and the ions can no longer penetrate between the parts – the parts only get coated from the front. In this particular example the coating uniformity would be achieved by 3-axis rotation of the parts. However, for more complicated geometries without any symmetry these effects could lead to non-uniform coating. At the same time, the shape of plasma sheath only affects ions, not the neutrals. Due to this, the ratio of deposited ions per deposited neutral (and subsequently the amount of deposited energy per deposited particle) can change with loading setup, causing the non-uniformity not only in coating thickness but also in its properties.