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Development of a classical force field for the oxidized Si surface

Application to hydrophilic wafer bonding
: Cole, D.J.; Payne, M.C.; Csanyi, G.; Spearing, S.M.; Ciacchi, L.C.

Postprint urn:nbn:de:0011-n-678628 (636 KByte PDF)
MD5 Fingerprint: 7f4d23f22d8a36cb869f4917eb731a41
Copyright AIP
Created on: 10.4.2009

The Journal of chemical physics 127 (2007), No.20, Art. 204704, 12 pp.
ISSN: 0021-9606
Journal Article, Electronic Publication
Fraunhofer IWM ()
wafer bonding; Si surface

We have developed a classical two- and three-body interaction potential to simulate the hydroxylated, natively oxidized Si surface in contact with water solutions, based on the combination and extension of the Stillinger-Weber potential and of a potential originally developed to simulate SiO2 polymorphs. The potential parameters are chosen to reproduce the structure, charge distribution, tensile surface stress, and interactions with single water molecules of a natively oxidized Si surface model previously obtained by means of accurate density functional theory simulations. We have applied the potential to the case of hydrophilic silicon wafer bonding at room temperature, revealing maximum room temperature work of adhesion values for natively oxidized and amorphous silica surfaces of 97 and 90 mJ/m(2), respectively, at a water adsorption coverage of approximately 1 ML. The difference arises from the stronger interaction of the natively oxidized surface with liquid water, resulting in a higher heat of immersion (203 vs 166 mJ/m(2)), and may be explained in terms of the more pronounced water structuring close to the surface in alternating layers of larger and smaller densities with respect to the liquid bulk. The computed force-displacement bonding curves may be a useful input for cohesive zone models where both the topographic details of the surfaces and the dependence of the attractive force on the initial surface separation and wetting can be taken into account.