Selective area electrodeposition Johanna Valio

Requirements in large scale micro/nano circuit industry low cost material efficiency few processing steps low temperature How to deposit Cu selectively on polymer substrate? Sawada et al. 2006; Franssila 2010, 55; Wisser et al. 2015

Electroless (autocatalytic) deposition Basics metal reduced without external current source chemical redox reaction in solution general reaction M z+ + R n− → M+ R z−n reducing agent oxidizes, metal reduces activation of the surfaces pH contol Benefits low T low cost fast uniform films Djokić 2011, 257; Niesen & DeGuire 2001; Franssila 2010, 55 Questions adhesion of Cu with PET can catalysts be avoided? pattern?

Patterning 1.silanol (–SiOH) group containing pre-layer -OH group reactive: capable of Si-O-Si bond formation 2.heating for smoothness & UV-radiation for wetting 3.immersion in toluene solution containing MPTS molecules: SAM layer with thiol (–SH) tail groups forms  Cu affinity 4.irradiation with UV through photomask deposition spots protected Sawada et al. 2006; Koumoto et. al 2008

Deposition of Cu substrate immersed in CuCl 2 solution complexing agent EDTA reducing agent DMAB NaOH for pH control  Cu deposited without a catalyst from a neutral solution Cu deposited on thiol spots Sawada et al. 2006

Problems? excess film growth deposition period must be optimized improving conductivity increasing grain growth, decreasing nucleation deposition rate optimation: not too fast for good adhesion hydrogen formation and incorporation to film hydrogen detection with Nuclear Reaction Analysis (NRA) Sawada et al. 2006; Franssila 2010, 56; Cui et al

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Controlling the electroless deposition process choice of reducing agent effects reaction kinetics, morphology and other properties of the deposited surface the risk of reduction reaction in the bulk solution in stead of substrate can be controlled with reducing agent concentration temperature and additive concentration also affect to thin film properties Djokić 2011

Self-assembled monolayers (SAM) can be used to tailor surface properties adsorp on the surface and arrenge for equilibrium can have different kind of head and tail groups (for example hydrophobic and hydrophilic) Ulman 1996

Prelayer and SAM dip coating of substrates in acetone+APTMS solution, heating in 120 C 5 min  silica-like layer toluene + MPTS solution: 1 h; heating 120 C in 5 min (residual solvent away + promoting the chemisorption of MPTS-SAM)  SAM with thiol group formed Sawada et al. 2006

References Cui, X., Hutt, D. A., & Conway, P. P. (2012). Evolution of microstructure and electrical conductivity of electroless copper deposits on a glass substrate. Thin Solid Films, 520(19), Djokić, S. (2011) (ed.) Modern aspects of electrochemistry, 48: Electrodeposition. Theory and Practice. Springer Science and Business Media. Franssila, S. (2010). Introduction to microfabrication. John Wiley & Sons. Koumoto, K., Saito, N., Gao, Y., Masuda, Y., & Zhu, P. (2008). Nano/micro patterning of inorganic thin films. Bulletin of the Chemical Society of Japan, 81(11), Niesen, T. P., & De Guire, M. R. (2001). Review: deposition of ceramic thin films at low temperatures from aqueous solutions. Journal of Electroceramics, 6(3), Sawada, S., Masuda, Y., Zhu, P., & Koumoto, K. (2006). Micropatterning of copper on a poly (ethylene terephthalate) substrate modified with a self-assembled monolayer. Langmuir, 22(1), Ulman, A. (1996). Formation and structure of self-assembled monolayers. Chemical reviews, 96(4), Wisser, F. M., Schumm, B., Mondin, G., Grothe, J., & Kaskel, S. (2015). Precursor strategies for metallic nano-and micropatterns using soft lithography. Journal of Materials Chemistry C, 3(12), Nuclear Reaction Analysis. Acquired