HiPIMS-CVD Hybrid Process for Advanced Functional Coatings: Proof of concept

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Magnetron sputtering is a physical vapour deposition (PVD) process extensively used in industry for the deposition of functional coatings for many applications. Although the process is able to deposit a wide range of functional materials including many oxides, nitrides and metals in complex multi-layer stacks with exceptional uniformity over large areas, deposition rates are relatively low, making the deposition of certain materials or products uneconomical. In addition, there are still some commercially important materials, such as aluminium oxide, which can cause severe processing instabilities (i.e. arcing, loss of anode surfaces, creation of negative ions, etc.), which restricts their usage. Plasma enhanced chemical vapour deposition (PECVD) is a competing process in which gaseous precursors form solid deposits on the substrate through reactions driven by energetic particles from the plasma. PECVD processes generally have the advantage of very high deposition rates, high conformity and low roughness, but are limited, largely by the available precursors, in the range of materials and complexity of the stacks that can be deposited. There are also limitations in uniformity over large area substrates.In order to reduce product cost and improve performance, there is a demand to improve upon the rate and, where applicable, the stability of the sputtering process and a similar demand for improving/expanding the material choice and uniformity of the PECVD process to open up new applications. An alternative means of achieving these goals is to combine the technologies simultaneously. This academic/industrial collaborative project is designed, therefore, to develop new hybrid deposition processes, combining the latest magnetron sputtering technologies with PECVD technologies for the high rate deposition of enhanced functional films, which are capable of scale-up and integration into existing large area inline deposition facilities to provide a new improved route to production, ideally at low temperature. The innovative approach taken here will be to use the HiPIMS (high power impulse magnetron sputtering) power delivery mode to drive both the magnetron and the CVD process. This is the first time that HiPIMS will have been used in this environment and this proposal is designed to act as a 'proof of concept' project. HIPIMS involves the application of very large power pulses to magnetron sputter cathodes for short periods. These intense pulses create high plasma densities, leading to a high degree of ionization of the sputtered species. The flux of coating material to the substrate can then be controlled by varying the magnetic field strength of the magnetron. Thus, adjustment of the magnetic array allows a means of controlling the flux of sputtered metal dopant to the growing CVD film, whilst still operating at the same pressure and time averaged power and, therefore, still maintaining the same plasma density in the process zone. The primary deliverable from this project will, therefore, be the development of a new method for the synthesis of functional films. This method will be validated through the deposition of carefully selected functional films relevant to industry and the characterisation of the deposition process.