Next generation high density plasma source for enhanced electron beam deposition of optical and nanostructured thin films over large areas
This is a continuation of a PhD project currently being completed by Dr David Child http://dx.doi.org/10.1016/j.surfcoat.2014.12.030. Project aims to investigate an innovative plasma source design concept offering enhanced plasma generation efficiency, remove the need for expensive consumables & componentry and provide an engineering solution which is compatible with retrofit into existing deposition systems. Being primarily developed by Thin Film Solutions Ltd (http://www.thinfs.com/technology.htm) and The University of the West of Scotland (http://www.uws.ac.uk/thinfilms/), the enhanced plasma source efficiency, self-sustaining operation and optimum pressure conditions for both hollow cathode and electron beam deposition of dense film microstructure at room temperature have been achieved.
A self-sustaining hollow cathode plasma source has been demonstrated to operate at deposition pressures of approximate to 2.0E-4 mbar, what is an order of magnitude lower than previously reported. This method uses a restrictor plate to create a higher pressure in a hollow cathode region with respect to the main deposition area. It is also demonstrated that ion energy distribution and current density at the substrate plane can be varied by changing the orifice geometry and/ or gas flow.
Comparison of IEDF’s at the substrates between multi-hole restrictor and single-hole restrictor plates
The plasma source investigation project continuation at Helia Photonics Ltd is taken over by UWS PhD student Jevgenij Mitrofanov under Dr Caspar Clark and Prof Des Gibson supervision. At the moment, project is mainly focused on the theoretical description of the next generation hollow cathode plasma source and experimental thin films properties investigation for industrial large area processes. Using the collected results, the initial theoretical model has been developed, describing the gas flow pressures, electromagnetic fields, charged particles trajectories and ion energy distribution functions at the growing material surface.
1 Modelled magnetic flux density inside the plasma source. Extractor current is 15 A, Induction coil is 60 A.
2 Modelled potential distribution inside the plasma source with grounded belljar and ground. Anode potential is 150 V, cathode potential is -50 V.
3 Modelled pressure inside the plasma source using 3.75 sccm in cathode gas inlet and 3.75 sccm in anode gas inlet. Temperature of the cathode surface is 2000 K.
4 Modelled Ar ion energy distribution function at the substrates for unrestricted plasma source.