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MEIS spectrum showing the La backscatter peak of after various anneals. La diffuses into the stack at elevated temperatures, resulting in a tail on the surface La peak. For the highest temperature anneals, an interface peak is observed. Inset shows simulations for La confined to the (solid curve), and La diffusion extending into the interlayer (IL).
La concentration in surface and interface regions as a function of annealing time. Filled symbols are surface concentrations, hollow symbols are IL concentrations. Line types correspond to different initial La coverages.
Schematic depiction of energy levels used to deduce the Fermi level position in the substrate and the metal/dielectric barrier. Positions are not drawn to scale.
Binding energies for Si2p (top) and Hf4f (bottom) core levels as a function of post-metal anneal temperature. Only samples that have been preannealed show a significant shift in the Si2p level, indicating that La indiffusion is needed to activate the threshold modification. On the right axis, binding energies are referenced to substrate Fermi level location (top) and metal-dielectric barrier (bottom).
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