Remote Plasma Sputtering of High Quality Thin Films for Advanced Functional Applications and Devices

Plasma Quest Ltd (PQL) has developed a patented remote plasma sputtering technology which deposits high quality, uniform thin films. As the plasma is generated remotely from the sputter target it offers advantages over other conventional sputtering techniques due to the independent control of the ion density and target bias. This allows a much wider sputter parameter space for the high rate deposition of both existing and new or complex materials and their associated thin film properties.

Although the novel technology already has many known benefits over other technologies, PQL continually strives to deepen its understanding of the complex and interrelated dynamics and properties of the plasma, sputter flux and thin film coatings, with the aim of offering enhanced coating capabilities. A recent MinMaT EngD revealed that a significant fraction of the sputter flux is continuously ionised by the high-density plasma. The inherent ionised physical vapour deposition (iPVD) nature of the process, in conjunction with substrate biasing, can be used to control the energy and direction of the ionised sputter flux. Thus, resulting in an even wider variety of thin film properties achievable and the ability conformally coat complex structures, including the underside of over-hanging structures by the process of re-sputtering.

The work involved in the proposed EngD will be focussed on developing a deeper understanding of the relationship between the plasma, sputter flux and thin film properties for potential enhancement of all aspects of the technology for successful commercialisation. This will include the development of the conformal coverage deposition process. As the process, using remote plasma sputtering, is still in its infancy, PQL needs to develop a more fundamental understanding of how it can be successfully implemented on a commercial level. Another area of research will lie in the optimisation of technology scale-up from R&D to industrial size. For commercialisation the maximisation of sputter flux transfer factor and deposition rate, whilst still maintaining the desired thin film properties over large area and at minimal energy consumption and cost per unit area conditions is particularly crucial to system purchasers.

For both areas of research, the interrelation between plasma, sputter flux and thin film properties can be achieved by systematic variation of the i) the plasma conditions; ii) deposition parameters; iii) deposition of a variety of thin film materials. Materials of interest include, but are not limited to, VO2 due to its thermochromic properties, with research previously conducted using PQL technology revealing that a modification of the phase transition temperature is possible and Al2O3 for its dielectric breakdown properties. Other general materials include transparent conducting oxides and dielectrics. Techniques available at the University to characterise the coating properties include SEM for morphology, EDX, Raman and XPS for composition, XRD for structure, AFM for surface roughness. OES for plasma and sputter flux analysis is available at PQL, along with UV-VIS-NIR spectroscopy, thin film stress and thickness measurement, optical and scanning electron microscopy, EDX and electrical resistivity.

From the empirical data collected the creation of a model relating all aspects of the deposition system variables to coating properties would be highly desirable.