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CPI Install Roll to Roll Digital Lithography Line to Develop OTFTs

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The Centre for Process Innovation (CPI) and Heidelberg Instruments have announced that they have developed a new high resolution, high speed roll to roll digital lithography tool for the manufacture of flexible organic thin film transistors (OTFT) used in next generation applications such as foldable display screens, sensors, integrated circuits and photo-detectors.

The machine, which is installed at CPI’s National Printable Electronics Facility in County Durham, is a significant stepping stone in the commercialisation of printable electronic devices because it provides the ability to continuously manufacture OTFTs directly onto rolls of plastic film at rates approaching 0.1 m2/min.

Across industry, products that use thin-film transistors with non-standard shapes and sizes or custom integrated circuits struggle to reach mass market adoption due to the high cost of manufacturing smaller volumes and the limitations imposed by print resolution and production speed.

Digital lithography, sometimes referred to as “laser direct imaging” or LDI, eliminates the need for photomasks by guiding a laser with computer generated imagery to directly expose light-sensitive material. This substantially reduces production time and lowers manufacturing cost, opening the technology up for shorter production runs and custom designs.

The key feature of the new tool is its ability to expose rolls of film with digital images generated in real time, thereby allowing it to dynamically compensate for any distortions present in each layer of the transistor as it is built up. It does this by using a optical exposure engine along with a laser and digital mirror device capable of through-putting up to 150 megabytes per second of image data.

The system is capable of four micron line and space resolution in the printed pattern using a print density equivalent to twenty five thousand dots per inch. It uses an exposure wavelength of 355 nanometers and is compatible with a wide range of standard i-line photoresist materials as well as being suitable for other UV-curing processes.

Speaking about the roll to roll digital lithography line, Dr Tom Harvey, Business Development Manager at CPI says:

“CPI has been establishing the capability and know-how to develop high performing flexible OTFTs for some time now. We have a qualified process for the manufacture of OTFT’s at batch scale. The new tool is available on an open access basis, allowing companies to progress their current sheet processes towards roll to roll production, enabling significant reductions in the costs and times associated with new product development of flexible OTFT arrays.”
Roland Kaplan, R&D Manger at Heidelberg Instruments, adds:

“We developed the write engine for this roll to roll lithography tool based on our experiences in high resolution optics, UV Laser and DMD technology. The main aspects were the modularity of the optical engine, the flexibility of the interfaces to the control system and the capability to handle the high speed data volume. The roll to roll lithography write engine perfectly fits into our family of maskless aligner tools which are commercially available at Heidelberg Instruments.”

The digital lithography line compliments existing organic semiconductor device manufacturing capability at CPI and it will also be of interest to companies who require high resolution continuous patterning of thin films on plastic. The project received financial assistance from Innovate UK through the European Commission’s ERA-NET Plus scheme OLAE+, project number 620063 along with sponsorship by the German Federal Ministry of Education and Research, funding program Photonics Research Germany, contract number 13N12635.