3-D sequential integration stands out from other 3-D schemes as it enables the full use of the third dimension. Indeed, in this approach, 3-D contact density matches with the transistor scale. In this paper, we report on the main advances enabling the demonstration of functional and performant stacked CMOS-FETs; i.e., wafer bonding, low temperature processes ( C) and salicide stabilization achievements. This integration scheme enables fine grain partitioning and thus a gain in performance versus cost ratio linked to separation of heterogeneous technologies on distinct levels. In this work, we will detail examples taking advantage of the unique 3-D contact pitch achieved with sequential 3-D.Index Terms-Low temperature process, molecular bonding, solid phase epitaxy, three-dimensional (3-D) integration, 3-D monolithic integration, 3-D sequential integration.
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.
3-D monolithic integration (3DMI), also termed as sequential integration, is a potential technology for future gigascale circuits. Since the device layers are processed in sequential order, the size of the vertical contacts is similar to traditional contacts unlike in the case of parallel 3-D integration with through silicon vias (TSVs). Given the advantage of such small contacts, 3DMI enables manufacturing multiple active layers very close to each other. In this work we propose two different strategies of stacking standard cells in 3-D without breaking the regularity of the conventional design flow: a) Vertical stacking of diffusion areas (Intra-Cell stacking) that supports complete reuse of 2-D physical design tools and b) vertical stacking of cells over others (Cell-on-Cell stacking). A placement tool (CELONCEL-placer) targeting the Cell-on-Cell placement problem is
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