[Zurück]

Ch. Lechner, H.C. Kuhlmann, F Holsteyns, A Lippert, M Junk:
"Removal of nano-particles from wafer substrates by hydrodynamical forces";
Poster: Workshop "Einführung in die Kontaktmechanik", SPP 1486 PiKo, Otto-von-Guericke-Universität, Magdeburg; 12.05.2011 - 13.05.2011.

The manufacturing of semi-conductor devices faces the challenge
of removing nano-particulate contamination from wafer substrates without
damaging high aspect ratio structures. A cleaning technique utilizing
hydro-dynamical forces to remove particles from the substrate
-- as e.g. ultrasonic cleaning -- therefore has to be
fine-tuned in order to avoid mechanical damage. Understanding the
underlying removal mechanisms in more detail is an essential step in
developing an efficient physical cleaning technique.

The goal of this project is to gain a better understanding of
the initiation of particle motion under the influence of hydro-dynamical
forces both experimentally and by means of modeling and numerical simulations.

For the numerical simulation we consider a sub-micron particle
adhering to the substrate. Due to its small size the particle is fully
immersed in the viscous sub-layer of the boundary layer, therefore
essentially facing a simple shear flow.
Concerning the interaction of the particle with the fluid
the particle is taken to be rigid and finite-sized, fully coupling to
the fluid. To this end we implemented an immersed boundary method
with direct forcing ([1], [2], [3]) in OpenFOAM [4].

For the interaction of the particle with the substrate we employ a
soft-contact model together with simple force-displacement relations [5].
Models for the normal force-displacement relation can be based on the
Johnson-Kendall-Roberts, Derjaguin-Muller-Toporov or Maguis-Dugdale models
for adhesion [6]. Appropriate models and experimental data
for tangential friction and rolling and torsion resistance are needed in
order to study the onset of particle motion.



References:

[1] M. Uhlmann, J. Comput. Phys., 209 (2005) 448-476

[2] S. Peskin, Acta Numerica, 11 (2002) 479-517

[3] K. Taira and T. Collonius, J. Comput. Phys. 225 (2007) 2118-2137

[4] see http://www.opencfd.co.uk/openfoam/

[5] see e.g. J. Tomas, Chem. Eng. Sci., 62 (2007) 1997

[6] see e.g. K. L. Johnson and J. A. Greenwood, J. Colloid Interface Sci.,192 (1997) 326 - 333