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Tthis prdel allows ths mainnpoiuseful surface a we

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Unformatted text preview: f lwe ofnowachirs ughtressutiond equilcanucalculate the Of che rtai,lthe Ghe sGan ssiproximation is eather crude, he d urfaces in t ou se of t au siau ap an. When w r measure t an s dsurface interaction energy. This principle was the main pointecomes less useful when the forces between the surfaces are istance. b with an AFM, we get a better description. In this case of the previously referred to paper of van Spengen et al [22].ery we g, becausecof tee setviatioof from the ht sampleutionnts’ for v weak t d s eth de S ns n ei real distrib p distanThs. nfexte partwctovs rsistribution,stwe can calcuis dthe cin the tail eof ahe iGarussian. Wahen we ‘heagure the surfacoi ce e I w kno hi e d the que to find th late istan e t ms es suisace utiteraction teonrgy.TThis prdel allows ths mainnpoiuseful surface a, we get a better description. In this case rftrib in on func i ne . inciple was u e to fi d nt with an AFM, d he mo otf ehe s,raviously ble erred dersaper ofevter Speatghapeteals[act]ually get a discrete set S of n ‘height sample points’ for t nd p end be a ref to unto p tand b t an wh n en p n 22 . we r a za © N. Dechev, University of Victoria za ¯ hb (z, zb ) = (7) 2 The Effective Contact Area Between Two Surfaces Example of capillary action between two rough surfaces: Capillary Condensation Between Two Contacting Surfaces Figure 5. N. Tas, et al.] condensation between two contacting Capillary [Image from surfaces. The meniscus curvatures are equal to the Kelvin radius; the contact angles satisfy Young’s equation. Note that the contact area A, and distance between the two surfaces d, general form, which is of thefor both the spreading and a are now a function valid surface roughness. Stiction in su water layers. Stengl et al [17] have c energy of about 100 mJ m−2 ba model. From wafer bonding expe stiction experiments [4, 20], adhesion and 270 mJ m−2 have been reported fo (T < 200 ◦ C). 2.3. Electrostatic forces between m Electrostatic attractive forces across from a difference in work functions charging of opposed surfaces [21, 1 the non-spreading condition [2]: For example, for polysilicon surfaces, the surface roughness the work function leads to the form typically has a value of Es to 3 nm Ab γla cos θC is considered to be 1 = C − 2 RMS. This (4c) double layer by a net transfer of elect highly smooth, and hence the high degree of stiction when contactthe other. Contact potentials are g to where γl a cos θC is the adhesion tension, and C takes into and the resulting surface charge dens is made. account the constant terms in (4a , b). The importance 1013 elementary charges per square of liquid mediated adhesion is supported by both stiction small separations the electrostatic p and friction experiments. Stiction of released structures 5 © N. Dechev, University of Victoria surfaces is 3generally lower than the v can show a large dependence on the relative humidity [21]. Temporary charging can occ of air [11]. Friction measurements of silicon and sil...
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