Roll to roll deposition of silicon nitride permeation barrier coatings using rotatable magnetrons 4.05

摘要

The deposition of water vapour permeation barriers on polymer films remains a major challenge for the introduction of various types of organic electronic devices. Multilayer coatings consisting of inorganic and organic layers have been proven to meet the extraordinary high requirements of the anticipated applications. However, the high price of these layer systems is still preventing a widespread commercial success. Therefore reducing the cost of such layers by developing effective deposition technologies remains a challenge for many research groups. The paper features a deposition technology for silicon nitride layers on polymer films. The focus of the experiments was placed on this material because it has already proven to be a suitable candidate for high performance water vapour barriers. The contribution will present results that had been achieved in a roll-to roll coating machine on 600 mm wide film. The described technology can be scaled up to industrially relevant sizes and hence has the potential for a substantial decrease of the deposition cost. The technology was developed on a module consisting of two rotatable sputter magnetrons. Silicon targets were sputtered in a gas atmosphere consisting of argon and nitrogen. It is well known that the achievable deposition rate in such processes strongly depends on a precise control of the sputter gas composition. Apart from this the authors could demonstrate that incorporation of residual reactive species into the forming layers depends on the process regulation as well. This parameter is eventually determining the optical dispersion relation as well as the achieved permeation properties. The catalytic activation of the nitrogen molecules on the partially metallic target surface was identified as a possible explanation of this behaviour. The dual magnetron system was run with a bipolar pulsed power of a frequency of 50 kHz and at a power level of 20 kW. Under these conditions the dynamic deposition rate amounted to 62 nm*m/min. Silicon nitride is distinguished by the fact that the optimum permeation barrier values can be achieved for a layer thickness below 100 nm. The lowest value of 6 × 10~(-3) g/m~(-2)day (38 °C, 90 % RH) could be demonstrated at for a single layer with a thickness of 75 nm on an OPTFINE PQA1 M substrate film. The paper will provide a comprehensive picture about both the details of the reactive sputtering process and the layer properties on different substrates.