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Research Papers

Fast Organic Conditioning of Patterned Surfaces for Capillary Part-to-Substrate Self-Assembly

[+] Author and Article Information
M. Mastrangeli1

 IMEC, Kapeldreef 75, B-3001 Leuven, Belgium; Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Leuven, Belgiummastrangelim@gmail.com

K. Jans, T. Steylaerts

 IMEC, Kapeldreef 75, B-3001 Leuven, Belgium

C. Van Hoof

 IMEC, Kapeldreef 75, B-3001 Leuven, Belgium; Department of ESAT, Katholieke Universiteit Leuven, Kasteelpark Arenberg 11, B-3001 Leuven, Belgium

J.-P. Celis

Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Leuven, Belgium

1

Present address: Distributed Intelligent Systems and Algorithms Laboratory (DISAL) of Ecole Polytechnique Fédérale de Lausanne (EPFL) Lausanne, Switzerland.

J. Electron. Packag 132(4), 041008 (Nov 24, 2010) (5 pages) doi:10.1115/1.4002725 History: Received March 29, 2010; Revised July 30, 2010; Published November 24, 2010; Online November 24, 2010

Selective chemical preconditioning of geometrically patterned substrates and parts is necessary to enable capillary part-to-substrate self-assembly. On the other hand, long preparation procedures may preclude the throughput enhancement potentially brought by the technique. In this paper, we investigate the fast chemical preconditioning of patterned substrates by the chemisorption of thiolates from the liquid phase. We found that even under conservative conditions, deposition times as short as 15 s (i.e., about two orders of magnitude shorter than previously reported in specific literature) are sufficient for the intended purpose, which is changing the wetting character of metallic binding sites enough to allow their selective dip-coating with hydrophobic fluid lenses. Moreover, perfect fluid coating conformality is achieved when such short deposition times are combined with the use of recessed binding sites. Our findings further confirm organic species to be remarkable tools for the chemical preconditioning of patterned surfaces as they may help actualize the full benefits of capillary self-assembly for electronic packaging.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Water CAs measured on DDT-functionalized Au test surfaces as function of DDT deposition time (24 h, 4 h, 2 h, 1 h, 30 min, 15 min, 5 min, 1 min, 45 s, 30 s, and 15 s). Average values and standard deviations of CAs out of at least ten measurements are shown for each deposition time.

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Figure 2

Dip-coating of hexadecane lenses on (a) superficial and (b) recessed (2) Au binding sites functionalized with 15 s-deposited DDT and patterned over silicon dioxide surfaces. Perfect coating conformality and excellent repeatability were always achieved in combination with recessed sites. Pictures were taken with substrates submerged in water after dip-coating. Colors and depth were enhanced by differential interference contrast (DIC) optical microscopy. Circular spots are the hexadecane bubbles floating on the surface of water (i.e., not pinned to the substrate) during pictures acquisition.

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Figure 3

Dip-coating of hexadecane on top of (a) uncleaned and (b) fully cleaned Au sites, both without any DDT functionalization. The dark spots in (a) are hexadecane lenses pinned to uncontrolled hydrophobic regions of the sites after dip-coating; they may also result from capillary break-up of former, larger hexadecane lenses (28). No hexadecane deposition was detected on cleaned substrates, as visible in (b). Pictures were taken with substrates submerged in water after dip-coating. Colors and depth were enhanced by DIC optical microscopy. Light circular spots are the hexadecane bubbles floating on the surface of water (i.e., not pinned to the substrate) during pictures acquisition.

Grahic Jump Location
Figure 4

Current-versus-potential curves after CV measurements on dodecanethiol-treated Au surfaces used as working electrodes. The electrical activity recorded for Au surfaces treated with a 1 min long DDT deposition is intermediate between the one corresponding to a blank and a full SAM-covered Au surface, as expected.

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Figure 5

FTIR spectra measured on dodecanethiol-treated Au samples. The shift in the absorption maxima located around 2920 cm−1 between 24 h and 1 min deposited organic layers is highlighted in the inset.

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