Nature of bonding forces between two hydrogen-passivated silicon wafers

Stokbro, Kurt; Nielsen, Eva Ravn; Hult, Erika; Andersson, Ylva; Lundqvist, Bengt I.

doi:10.1103/physrevb.58.16118

Cited by 7 publications

(6 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This value is again in line with the work of separation that can be calculated using both attractive and repulsive parts of the force: Considering the longer range of the attractive van der Waals part only (which is dominant in the collapsed regime) A/12πd 2 , one obtains a factor of (d 1 /d 2 ) 2 =10 in the energies, consistent with the observed E 2 /E 1 ratio. Note that more exact formalisms developed from ab-initio calculations [26] predicted energies in the range of the observed one for the collapsed situation, in contradiction with measurements that were done using HF-last surface samples. Hence, the reported discrepancies between energy calculations and measurements could be manifestations of the effect of short wavelength surface roughness with the presence of an asperity gap.…”

Section: ]contrasting

confidence: 58%

Interfacial closure of contacting surfaces

Rieutord¹,

Rauer²,

Moriceau³

2014

EPL

View full text Add to dashboard Cite

Understanding the contact between solid surfaces is a long standing problem which has a strong impact on the physics of many processes such as adhesion, friction, lubrication and wear. Experimentally, the investigation of solid/solid interfaces remains challenging today, due to the lack of experimental techniques able to provide sub-nanometer scale information on interfaces buried between millimeters of materials. Yet, a strong interest exists improving the modeling of contact mechanics of materials in order to adjust their interface properties (e.g. thermal transport, friction). We show here that the essential features of the residual gap between contacting surfaces can be measured using high energy Xray synchrotron reflectivity. The presence of this nano-gap is general to the contact of solids. In some special case however, it can be removed when attractive forces take over repulsive contributions, depending on both height and wavelength of asperity distributions (roughness). A criterion for this instability is established in the standard case of van der Waals attractive forces and elastic asperity compression repulsive forces (Hertz model). This collapse instability is confirmed experimentally in the case of silicon direct bonding, using high-energy X-ray synchrotron reflectivity and adhesion energy measurements. The possibility to achieve fully closed interfaces at room temperature opens interesting perspectives to build stronger assemblies with smaller thermal budgets.

show abstract

Section: ]contrasting

confidence: 58%

Interfacial closure of contacting surfaces

Rieutord¹,

Rauer²,

Moriceau³

2014

EPL

View full text Add to dashboard Cite

show abstract

“…Hence, it is less important for hydrogenated Si surfaces, where the hydrogen-hydrogen interaction is prominent as evidenced in the surface (ground-state) structures. 56,59 The efforts to understand the surface mechanics using experimental 60 and simulated 61 nanoindentation provide qualitative descriptions but the accurate (size-dependent) Young's modulus or the surface elastic constants have proved difficult to access via this indirect technique, leading to a need for direct measurement. In the work presented here first-principles calculations are crucial to deal properly with quantum mechanical effects such as the hydrogen-hydrogen interaction, and to investigate directly the size-dependent mechanical properties of the hydrogenated surface in a quantitative sense.…”

Section: B Surface Propertiesmentioning

confidence: 99%

“…Other definitions of the bounding surface exist: for example, the midplane between two identical H-passivated surfaces at their minimum energy separation. 59 Had we taken a different definition of the crosssectional area, the apparent size dependence of E would have been different, an ambiguity associated with describing discrete atomic systems with continuum mechan-ics. To illustrate the issue, consider the effect on the size dependence of E from changing the definition of crosssectional area by modifying the position of the surface r by δr as shown in Fig.…”

Section: Geometry Of Nanowiresmentioning

confidence: 99%

First-principles calculation of mechanical properties of Si⟨001⟩ nanowires and comparison to nanomechanical theory

2007

View full text Add to dashboard Cite

We report the results of first-principles density functional theory calculations of the Young's modulus and other mechanical properties of hydrogen-passivated Si 001 nanowires. The nanowires are taken to have predominantly {100} surfaces, with small {110} facets according to the Wulff shape. The Young's modulus, the equilibrium length and the constrained residual stress of a series of prismatic beams of differing sizes are found to have size dependences that scale like the surface area to volume ratio for all but the smallest beam. The results are compared with a continuum model and the results of classical atomistic calculations based on an empirical potential. We attribute the size dependence to specific physical structures and interactions. In particular, the hydrogen interactions on the surface and the charge density variations within the beam are quantified and used both to parameterize the continuum model and to account for the discrepancies between the two models and the first-principles results.

show abstract

“…It is achieved by contacting the prepared hydrophobic wafers under clean conditions and with a moderate pressure. Recent calculations 4 suggest that the bonding forces in this regime are long-range van der Waal forces between the outermost Si atoms, which are kept apart by repulsive forces between the adsorbed hydrogen atoms. Next, between 150 and 300°C the bond energy increases slowly, possibly due to diffusion of weakly bound surface contaminants or formation of H-F-H or H-O-H bridges between the wafers.…”

Section: Fusion Bonding Of Si Wafers Investigated By X Ray Diffractionmentioning

confidence: 99%

Fusion bonding of Si wafers investigated by x ray diffraction

Weichel

Grey

Rasmussen

et al. 2000

Applied Physics Letters

View full text Add to dashboard Cite

The interface structure of bonded Si(001) wafers with twist angle 6.5 ° is studied as a function of annealing temperature. An ordered structure is observed in x-ray diffraction by monitoring a satellite reflection due to the periodic modulation near the interface, which results from the formation of a regular array of screw dislocations. This satellite reflection first appears at an annealing temperature of 800 °C, and increases abruptly up to temperatures of 1000 °C. We propose that this transition occurs when there is sufficient mobility for the reorganization of atomic steps and terraces in the interface region.

show abstract

Nature of bonding forces between two hydrogen-passivated silicon wafers

Cited by 7 publications

References 24 publications

Interfacial closure of contacting surfaces

Interfacial closure of contacting surfaces

First-principles calculation of mechanical properties of Si⟨001⟩ nanowires and comparison to nanomechanical theory

Fusion bonding of Si wafers investigated by x ray diffraction

Contact Info

Product

Resources

About