Bonding energy represents an important parameter for direct bonding applications as well as for the elaboration of physical mechanisms at bonding interfaces. Measurement of bonding energy using double cantilever beam (DCB) under prescribed displacement is the most used technique thanks to its simplicity. The measurements are typically done in standard atmosphere with relative humidity above 30%. Therefore, the obtained bonding energies are strongly impacted by the water stress corrosion at the bonding interfaces. This paper presents measurements of bonding energies of directly bonded silicon wafers under anhydrous nitrogen conditions in order to prevent the water stress corrosion effect. It is shown that the measurements under anhydrous nitrogen conditions (less than 0.2 ppm of water in nitrogen) lead to high stable debonding lengths under static load and to higher bonding energies compared to the values measured under standard ambient conditions. Moreover, the bonding energies of Si/SiO2 or SiO2/SiO2 bonding interfaces are measured overall the classical post bond annealing temperature range. These new results allow to revisit the reported bonding mechanisms and to highlight physical and chemical phenomena in the absence of stress corrosion effect.

International audienceDuring direct bonding, a thin gas film is trapped in-between the two wafers, leading to an interactive fluid/structure dynamics. A model of bonding dynamics is formulated using the plate approximation, Reynolds equation, and adhesion forces as the boundary condition at the bonding front. The transient equation is solved numerically in a one dimensional cylindrical case. The entire process, including initiation and propagation of the front, is modelled. The model is supported by experimental data from an original setup involving non-contact optical sensors to measure the vertical movement of the wafer during the bonding sequence. (C) 2013 AIP Publishing LL

The wafer bonding has been established as a key process used for the fabrication of silicon-on-insulator (SOI) substrates. In the present paper an overview of the fundamental aspects involved in the wafer bonding process is presented. The mechanisms of the silicon and silicon oxide bonding are discussed with an emphasis on the phenomenological models developed in case of SOI bonding. Interactions between the mechanical adhesion and the dynamics of the interface chemistry and their impact on the bonding modeling are also discussed. One of the main challenges today is the validation of existing models and the comparison of physical measurements with the advanced modeling results.

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Direct bonding energy is an important parameter for direct bonding applications as well as for mechanism elaboration. Thanks to its simplicity as well as for its simple result interpretation, double cantilever beam (DCB) under prescribed displacement is the most used technique to measure the direct bonding energy. But, as shown also in this study, measurement of Si/SiO 2 or SiO 2 /SiO 2 direct bonding in standard humid atmosphere is greatly impacted by water stress corrosion. To prevent this effect, bonding energies have been evaluated under anhydrous atmosphere with less than 0.2ppm of water in nitrogen. After the setup and methodology description of the bonding energy measurement without stress corrosion influence, the global classical Si/SiO 2 and SiO 2 /SiO 2 direct wafer bonding energy curves versus post-bonding annealing temperature are revisited. Moreover, by using various surface treatments prior to bonding, the bonding energy behavior according to post-bonding annealing can drastically change as for example with plasma surface activation treatment. But in contrary, silicon-silicon hydrophobic bonding energy seems not impacted by the measurement atmosphere. Such results will also be presented and discussed.