Thin-film inkjet printing

Hong, C. Wagner, S. 2000. Inkjet printed copper source/drain metallization for amorphous silicon thin-film transistors. IEEE Electron Dev. Lett. 21 384-386. 

Kaydanova, T. Miedaner, A. Perkins, J. D. Curtis, C. Alleman, J. L. Ginley, D. S. 2007. Direct-write inkjet printing for fabrication of barium strontium titanate-based tunable circuits. Thin Solid Films 515 3820-3824. 

While these polymeric materials hold promise for low-cost electronics and simplified device processing, they still suffer from lower performance than conventional inorganic semiconductors. As the development of these novel materials continues, an alternative technology incorporating patterning schemes such as inkjet printing and conventional vacuum deposited thin films, may provide the required overlap of performance with low-cost fabrication of microelectronic circuits on large-area platforms. 

The TFT fabrication process on glass substrates starts with 100 nm of Cr for the gate metal, and is followed by a PECVD 200 nm thick Si3N4 dielectric with a 30 nm thick SiC>2 surface layer. The source drain metal is Cr/Au. Each of these layers is patterned using printed wax masks and chemical etching, steps a to d in Fig. 11.8. The surface is modified with a solution deposition of a self-assembled monolayer of octyltrichlorosilane (OTS-8) before inkjet printing deposition of the semiconductor. It has been shown that the OTS-8 layer affects the structural order of PQT-12 in thin films, improving the performance of the TFT [23]. Encapsulation and possibly other subsequent layers may be needed on the TFT, but these are not discussed here. 

Another major technology area that can utflize conductive IJ ink is the display market. Inkjet can be applied for both flexible and rigid displays such as electroluminescent and electrophoretic displays (including e-paper), hquid crystal displays (LCD), plasma display panels (PDP) and touch screens some functionalities have already been printed by IJ technology in certain display apphcations, for example RGB color filters. Conductive IJ is also appropriate for use in thin film transistors (TFT), disposable batteries, radio-frequency identification (RFID) tags, and a range of chemical and electronic sensors. 

Inkjet Can print thin films and fine features. Amenable to prototyping. Digital customization. Specific equipment designs for electronics. Non-contact method. Low throughput. Complex systems. Major equipment suppliers include Fujifihn Dimatix, HP, Litrex, Xennia/Carlco, Xaar, Ricoh. 

In the near future, we expect to see adoption and adaptation of inkjet technology to rapidly growing markets such as photovoltaics, OLEDs, and thin film transistors. In general, the development of flexible printed electronics for a wide range of applications is expected to take advantage of the value proposition of inkjet printing of conductive inks. 

Liu Z, Su Y, Varahramyan K. (2005) Inkjet-printed silver conductors using silver nitrate ink and their electrical contacts with conducting polymers. Thin Solid Films 478 275-279. 

Burns SF, Cain P, Mills J, Wang JZ, Sirringhaus H. (2003) Inkjet printing of polymer thin-film transistor circuits. MRS Bulletin 28(11) 829-834. 

Kawase et al. [17] fabricated All-polymer thin film transistors by inkjet printing technique. They used these transistors as active-matrix backplane for information displays. This field has been dominated by amorphous Si TFTs and large liquid crystal displays with an amorphous Si TFT active matrix backplane have been manufactured at a reasonable cost. An organic TFT is expected to reduce the cost even more, and to be applied to flexible displays based on a plastic substrate. The TFT characteristics required for active-matrix displays are (1) sufficient drain cmrent, (2) low off current, (3) low gate leakage current through an insulator, (4) small gate overlap capacitance and (5) uniform characteristics. 

M. F. Mabrook, C. Pearson, M. C. Petty, Inkjet-printed polypyrrole thin films for vapour... 

Kawase, T. et al., Inkjet printing of polymer thin film transistors, Thin Solid Films 438,... 

Inkjet Printed Organic Thin Film Transistors... 

Teichler A, Eckardt R, Friebe C, Perelaer J, Schubert US. Film formation properties of inkjet printed poly(phenylene-ethynylene)-poly(phenylene-vinylene)s. Thin Solid Films 2011 519(11) 3695-702. 

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