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Three-dimensional multi-channel field-effect transistor (MCFET) gate stack and series resistance are investigated and optimized by specifically developed integration processes, characterization methods, and numerical simulations. First, the impact of a TiN/HfO2 gate stack on embedded-gate MCFET structure performance is studied. Both TiN/SiO2 and N+poly-Si/SiO2 gate stacks were introduced in the MCFET to compare the carrier mobility behavior (300 K down to 20 K), the gate leakage current, and the negative bias temperature instability. The obtained electrical data are then compared with a planar FD-SOI reference, highlighting some specific challenges linked to the introduction of a high- kappa/metal gate stack in embedded cavities. On the other hand, it is shown how the series resistance is intrinsically increased by the 3-D configuration. We also show how this increase can be attenuated significantly by optimizing the source/drain (S/D) shape, the implantation conditions, and the S/D silicide position.
Date of Publication: June 2009