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Low-temperature hydrophobic silicon wafer bonding Appl. Phys. Lett. 83, 4767 (2003); 10.1063/1.1632032Yttrium silicate formation on silicon: Effect of silicon preoxidation and nitridation on interface reaction kinetics Low-temperature anodic oxidation of silicon using a wave resonance plasma sourceWe present the results of an infrared ͑IR͒ spectroscopic investigation of interfaces between two hydrophilic Si wafers bonded at low temperature. Multiple internal transmission IR spectra were recorded of the bonds, with different chemical pretreatments of Si surfaces employed before bonding. The analysis of IR spectra shows that the number of O-H and H-Si-O x species at the interface depends strongly on the chemical pretreatment type, which determines the bonding energy. The annealing procedure used in the bonding process leads to dissociation of water molecules, oxidation of silicon at the interfaces, and diffusion of hydrogen into silicon oxide layer formed at the interface. The difference in bonding processes is discussed.

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High quality dilute nitride subcells for multijunction solar cells are achieved using GaInNAsSb. The effects on device performance of Sb composition, strain and purity of the GaInNAsSb material are discussed. New world records in efficiency have been set with lattice-matched InGaP/GaAs/GaInNAsSb triple junction solar cells and a roadmap to 50% efficiency with lattice-matched multijunction solar cells using GaInNAsSb is shown.

Based on the fracture mechanics analysis of crack propagation, the phenomenon of subcritical crack growth was utilized for a controlled debonding of directly wafer-bonded interfaces. The approach allowed the well-defined separation of bonded wafers although the bond strength was high due to thermal annealing. The achieved splitting velocity depended on the wafer material, the wafer thickness ratio, the bonding process parameters, and the environmental conditions during cleaving. In combination with wafer bonding, the method can be used for a temporary stiffening and handling of thin and brittle wafers during fabrication, even if the wafers are exposed to high process temperatures. The approach can also be applied to fabricate micromechanical systems (MEMS

Multiple internal reflection and transmission IR spectra of hydrophobic and hydrophilic Si wafers, Si wafers with thermally grown SiO 2 layers, and Si wafers bonded at high and room temperature were investigated. It was found that the surface of the as-prepared hydrophobic wafer is terminated by hydrogen and water molecules, while the IR spectra of hydrophilic wafer demonstrate only the presence of water molecules at the surface. IR spectra of Si wafers covered by a thermally grown SiO 2 layer exhibit a number of the strong absorption bands assigned to combinational phonon bands in SiO 2 . The wafer bonding leads to the appearance of siloxane and hydroxyl groups at the buried interface whose absorption bands were observed in IR spectra. A rearrangement of atoms at the buried interface takes place after annealing of Si bonded wafers. IR spectra of room temperature bonds show a large number of water molecules and presence of the hydrogen in the oxide layer at the interface.

In this paper, intermediate layer bonding technologies using SU-8 and BCB are successfully demonstrated. The bonding process, which consists of only several simple steps such as material deposition, exposure and development, as well as contact and bonding, can be carried out in a bonder at low temperature, e.g., somewhere between 120°C and 350°C. Benefits from this, integration of metal electrodes and wires between the bonding interfaces becomes possible. Moreover, since adhesive bonding does not necessitate extremely smooth contact surface, nor does it rely on the cleanliness of ambient environment, it is possible to carry out this process in a standard chemistry lab, and join different substrates without any pre-treatment. Initial inspection results showed that this method has a satisfactory yielding rate of more than 90%, and an acceptable bonding strength of above 2 MPa. The minimal thickness of the adhesive layer, which should retain the chips together after dicing, can be reduced to values between 6-10μm. For low-cost capacitive transducers, this is an attractive packaging technology. On the other hand, because SU-8 epoxy is an innovative building block for polymer devices, this method can also be used to construct complex micro systems.