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Electroplated copper exhibits some surprising changes at room temperature in sheet resistance, stress, and microstructure. This behavior, now known as self-annealing, is shown here to be intimately linked to the composition of the plating bath and the resulting incorporation of organic additives in the Cu layer. Their addition is a necessary condition for self-annealing to occur, but slows down the process for higher concentrations. The phenomenon also depends critically on film thickness, showing an accelerated transformation when film thickness increases. This dependence is explained in terms of a very rapid primary crystallization from the top surface down just after deposition, followed by a slower lateral recrystallization producing large secondary grains. The stress and sheet resistance during recrystallization are identified as two noncorrelated variables.

For the first time the maximum thermal budget of in-situ doped source/drain State Of The Art (SOTA) FDSOI bottom MOSFET transistors is quantified to ensure transistors stability in Sequential 3D (CoolCube TM ) integration. We highlight no degradation of Ion/Ioff trade-off up to 550°C. Thanks to both metal gate work-function stability especially on short devices and silicide stability improvement, the top MOSFET temperature could be relaxed up to 500°C. Laser anneal is then considered as a promising candidate for junctions activation. Based on in-depth morphological and electrical characterizations it demonstrates very promising results for high performance Sequential 3D integration.

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