A model is presented which relates the applied load and surface roughness to the integrity of metal-metal wafer-level thermocompression bonds. Using contact theory, the true contact area is calculated as a function of the applied load and surface roughness as characterized using atomic force microscopy. The relationship between the nominal and true contact areas quantifies the effects of applied load and surface roughness on the bond integrity of the bonded wafers as indicated by the dicing yield. Experiments on Cu–Cu bonds show that the true contact area provides a better indicator of bond integrity than either the nominal contact area or applied force, taken together or separately.

Ultraviolet photodetector with p-n heterojunction is fabricated by magnetron sputtering deposition of n-type indium gallium zinc oxide (n-IGZO) and p-type nickel oxide (p-NiO) thin films on ITO glass. The performance of the photodetector is largely affected by the conductivity of the p-NiO thin film, which can be controlled by varying the oxygen partial pressure during the deposition of the p-NiO thin film. A highly spectrum-selective ultraviolet photodetector has been achieved with the p-NiO layer with a high conductivity. The results can be explained in terms of the "optically-filtering" function of the NiO layer.

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