1 Laser cleaning
The implementation of many industrial processes requires precise control of the different surfaces involved in the processes. Cleaning is one of the major steps of preparation of these surfaces. Today, most of the cleaning techniques are based on mechanical or chemical techniques. These techniques are not suitable for flexible organic electronics, and new processes need to be implemented. Photonic techniques, like laser or plasma, are very attractive for this application. They are contact-free processes that do not generate any secondary wastes. And can be remotely operated for the treatment of flexible substrate (not sensitive to distance variations), even in roll-to-roll mode.
The laser cleaning process has previously demonstrated its effectiveness (Delaporte & Oltra, 2006) in many fields of applications like microelectronics (Grojo, Cros, Delaporte, & Sentis, 2007; Tam, Park, & Grigoropoulos, 1998) or nuclear decontamination (Delaporte et al., 2003), and for different substrates like polymers (Fourrier et al., 2001) and optical surfaces (Pleasants & Kane, 2003). Photoacoustic stress waves (Soltani & Ahmadi, 1994), photothermal vaporization, and near-field enhancement (Grojo et al., 2012; Mosbacher et al., 2001) are the main processes for the removal of particles and thin films of liquid (Grojo, Delaporte, Sentis, Pakarinen, & Foster, 2008; Vatry et al., 2011). Photochemical effects induced by UV laser irradiation are also efficient for organic contamination removal, like fingerprints (Lu, Komuro, & Aoyagi, 1994).
In flexible organic electronics cleanliness is less critical than in the silicon microelectronic industry.
Because the typical sizes are larger and the manufacturing less sensitive to smaller contamination. Nevertheless, the surfaces need to be free of contamination to ensure good electrical contact and good adhesion between the successive layers. It is also important to get rid of any particles from light emitting surfaces (OLED) to avoid black, or even bright, spot effect on the display. After etching or via drilling steps, some debris also has to be removed. Laser processes can be successfully use for these cleaning applications with a good choice of the irradiation parameters.