Big improvements are needed in the manufacturing yields for roll-to-roll (R2R) production of plastic and large-area electronics. Now an EC-funded consortium of European companies and research institutes is tackling the issue.
Coordinated by TNO/Holst Centre in the Netherlands, Clean4Yield is focused on contamination and defect control in R2R organic electronics production.
Minimising materials waste
In the conventional microelectronics industry - such as LCD display production - yields are high, the result of successive investment in production and analysis techniques as the industry has scaled. R2R fabrication of electronic devices, such as OLED panels and organic photovoltaics (OPVs), is incredibly materials-intensive.
Developers are looking for cost-effective production yields of higher than 95%, to minimise wastage of expensive substrates, chemicals, metals and other materials.
Project coordinator Juliane Gabel says: 'This industry is in the pre-pilot stage and developers do not want to share their yield information, but there is a reluctance to move towards volume production until technologies for identifying and repairing defects are developed. Companies have been calling for this project.'
Improving yields in R2R electronics production requires technologies that can identify defects dust particles down to the smallest sizes.
Gabel notes: 'If there are lots of defects then the process needs to be worked on. On the other hand if a defect is identified, then repairing may be more cost-effective then scrapping output.'
Technologies that can clean and repair device substrates and layers will also be developed. In the course of the project partners will learn which particles are most problematic, and techniques for preventing dust particles reaching the substrates in R2R production environments.
Plastic attracts dust particles, which can cause problems in the short-term, but also problems that can get worse over time and lead to device malfunction. A pinhole defect in a barrier layer can enlarge if left unchecked.
Gabel adds: 'Even smallest particles pose problems by disturbing the homogeneity of these very thin, nano-scale layers.'
Clean4Yield's approach will encompass problems that are common to both OLEDs and OPVs, which have commonalities in production, and which will also be relevant to other flexible or large-area electronic device manufacturing in future.
The ultimate goal of the three-year project is to show and demonstrate new yield technologies in-line. Several partners, including Eight19 and Philips are involved in manufacturing production; Eight19, for instance, is a UK-based developed of polymer solar cells using R2R production techniques.
Other partners, including Dr Schenk, Orbotech and Horiba Jobin Yvon, provide inspection and analysis tools used in manufacturing silicon and thin-film electronics. Dr Schenk's metrology systems are already used by Heliatek, a developer of organic solar cells based on small molecules. However electronics based on polymer organic semiconductors pose unique challenges.
Gabel explains: 'The idea is to adapt and stretch these existing techniques. Delft University of Technology, another partner in the consortium, has carried out work which can support further development of these existing techniques, and the Holst Centre itself has a wealth of experience in R2R processing of OLED lighting and organic solar cells.'
Other partners include plastic substrate supplier DuPont Teijin Films and Coatema, a developer of R2R equipment for producing organic and printed electronic devices. In all, 16 partners are involved in Clean4Yield.
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This three-year, EU-funded project aims to improve the yields of roll-to-roll manufacturing for plastic electronics
The Belgian R&D centre is working on organic electronic technologies