Bonding silicon wafers with reactive multilayer foils

In this study, silicon wafers were bonded using Ni/Al reactive multilayer foils as local heat sources for melting solder layers. Exothermic reactions in Ni/Al reactive multilayer foils were investigated by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). XRD measurements showed that the dominant product after exothermic reaction was ordered B2 AlNi compound. The heat of reaction was calculated to be -57.9 kJ/mol. A numerical model was developed to predict the temperature evolution in silicon wafers during the bonding process. The simulation results showed both localized heating and rapid cooling during the reactive foil joining process. Our experimental observation showed that the bond strength of the silicon wafer joints was estimated to be larger than the failure strength of bulk silicon. Moreover, leakage test in isopropanol alcohol (IPA) showed that reactive foil bonds possessed good hermeticity. (c) 2007 Elsevier B.V. All rights reserved.