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XTEM images of FUSI capacitors with different Co:Ni ratios. FUSI is confirmed when a uniform layer of Co–Ni slicide is observed. The inserted high-resolution XTEM images show the good quality of the gate/oxide interface.
Sheet resistances of undoped, As-doped, and B-doped Co, Ni, or Co–Ni silicides. increases when the Co content increases in the silicides.
(a) Glancing angle XRD shows phase formations in the Co–Ni silicides. Both Co and Co-Ni phases are observed in all three samples. The peak densities of Co phases increase while those of Co–Ni phases are decrease with Co percentage. (b) SIMS depth profile of three Co–Ni FUSI samples. The peak value of each dopant is labeled at the bottom of each graph. Different Co:Ni ratios are found at the gate/oxide interface, as well as dopant segregation.
(a) Extrapolated work functions of undoped, As-doped, and B-doped Co, Ni, and Co–Ni silicides. A linear relationship is found with the Ni percentage in undoped FUSI gates, while As-doped and B-doped gates have nearly identical work functions. (b) Reasonable leakage current density are found in all three Co–Ni silicides, while the has lowest leakage current density among the three.
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