| AVS 65th International Symposium & Exhibition | |
| Thin Films Division | Thursday Sessions |
| Session TF+AS+EL+EM+NS+PS+SS-ThA |
| Session: | IoT Session: Thin Films for Flexible Electronics and IoT |
| Presenter: | Bryan Stuart, University of Oxford, Department of Materials, UK |
| Authors: | B.W. Stuart, University of Oxford, Department of Materials, UK T. Cosnahan, University of Oxford, Department of Materials, UK A.A.R. Watt, University of Oxford, Department of Materials, UK H.E. Assender, University of Oxford, Department of Materials, UK |
| Correspondent: | Click to Email |
Vacuum metallisation of aluminium through shadow masks has been commercially used for decades for depositing electrodes on rigid semiconductor devices, however recent developments have enabled large area, continuous deposition of patterned metallization in the aesthetic printing industry and has the potential for electrode interconnects for devices on flexible substrates such as Polyethylene Terephthalate (PET) and Polyethylene Naphthalene (PEN). Flexible polymer webs of PET were coated (SeeSupplementary Figure) with 50 nm thick, 165 um wide aluminium electrodes by commercially compatible manufacturing at roll-to-roll web speed of 2.4 m min-1 showing tremendous potential for large scale manufacturing of wearable electronic devices in transistors, low level energy generation (Thermoelectric generators), energy storage (thin film batteries) or display technologies (LED displays) [1].
The in-line patterning process relies on adaptation of flexography ink printing which typically transfers ink to a rubber patterned plate for printing images onto polymer webs. The flexibility of the printing plate accommodates for irregularities in the surface of the substrate making this process desirable for large area manufacturing. Metallization has been used to deposit aluminium onto a flexography applied pattern by replacing ink with a low vapor pressure oil (e.g. Perfluropolyether, Krytox®). The radiative heating of aluminium metallization causes simultaneous evaporation of the oil pattern, thereby rapidly forming the desired metal pattern onto the un-patterned regions. Currently we are scaling-up the oil flexography/metallization process into an industrial-scale roll-to-roll coater with potential web widths of 350 mm and roll speeds of 100 m min-1, in order to increase web speeds, and to expand the range of materials deposited and the functional devices to which they are applied.
This paper reports on in-line pattern deposition of aluminium and other materials as applied to functional devices, for example organic thin film transistors and thermoelectric devices. In particular we are able to demonstrate how the process can be compatible with other functional layers. We will report our studies of electrode precision (shapes/sizes) by patterned metallization and our first studies of sputtering with flexography patterning. The long term view is integration of this technology along the R2R production path for single pass/high speed production of low cost and flexible integrated circuits.
References
1. Cosnahan, T., A.A. Watt, and H.E. Assender, Modelling of a vacuum metallization patterning method for organic electronics. Surface and Coatings Technology, 2017.