Suppression of cobalt silicide agglomeration using nitrogen (N/sub 2//sup +/) implantation
In this paper, the effects of nitrogen coimplantation with boron into p/sup +/-poly gate in PMOSFETs on the agglomeration effects of CoSi/sub 2/ are studied. The thermal stability of CoSi/sub 2//poly-Si stacked layers can be significantly improved by using nitrogen implantation. Samples with 40-nm cobalt silicide (CoSi/sub 2/) on 210-nm poly-Si implanted by 2/spl times/10/sup 15//cm/sup 2/ N/sub 2//sup +/ are thermally stable above 950/spl deg/C for 30 s in N/sub 2/ ambient. If the dose of nitrogen is increased up to 6/spl times/10/sup 15//cm/sup 2/, the sheet resistance of CoSi/sub 2/ film is not increased at all, and TEM photographs show that the agglomeration of CoSi/sub 2/ film is completely suppressed.
Uniform CoSi2 nano-nucleus formation by oxide mediated silicidation with a Ti capping layer
The nucleation stage toward CoSi2 with average island size of about 4 nm and uniform island size distribution is obtained from a TiN/Co/ Ti/Co/SiOx/Si multilayer with the SiOx as a mediated layer by annealing at 460 -C for 240 s followed by 600 -C 240 s. It is found that Ti capping layer can enhance Co diffusion into the Si substrate at higher temperature (600 -C 240 s) annealing, which results in larger nucleus size (average grain size about 12 nm) but nonuniform nucleus size distribution. However, two-step annealing for 460 -C 240 s followed by 600 -C 240 s results in a smaller average nucleus size with better nucleus size distribution. The mechanism responsible for the discrepancy is discussed in the paper. D 2005 Elsevier B.V. All rights reserved.
Explicit solutions for N-dimensional Schrödinger equations with position-dependent mass
With the consideration of spherical symmetry for the potential and mass function, one-dimensional solutions of nonrelativistic Schrodinger equations with spatially varying effective mass are successfully extended to arbitrary dimensions within the frame of recently developed elegant nonperturbative technique, where the BenDaniel-Duke effective Hamiltonian in one dimension is assumed like the unperturbed piece, leading to well-known solutions, whereas the modification term due to possible use of other effective Hamiltonians in one dimension and, together with the corrections coming from the treatments in higher dimensions, are considered as an additional term like the perturbation. Application of the model and its generalization for the completeness are discussed.