Specific Process Knowledge/Bonding/Fusion bonding
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Fusion Bonding
Fusion bonding is a relative weak bond between e.g. two clean Si wafers. It is absolutely necessary for the wafers to be very clean and to be annealed at 1000°C afterwards to avoid and minimize defects. Fusion bonding can be made as a Si to Si direct bonding or with SiO layers in between. It is also possible to use nitride in between but it should be close to 100% particle free. We have good experience with Sintef but unfortunately not with the old DTU Nanolab nitride furnace.
Try and put a fusion bonding as early in a process sequence as possible, since during annealing is not possible to have any kind of metals on your wafer. Furthermore the thermal budget could drive dopants further into the wafer than wanted.