Nanoscale epitaxial cobalt salicide bitlines for charge trappingmemory cells

An epitaxial Co Si 2 process is presented, which allows the self-aligned formation of bitlines with only a few tens of nanometer width for Twin Flash memory cells in the 63 nm generation. The bitlines show a good thermal stability and low resistance for widths down to 35 nm , where polycrystalline Co Si 2 is known to exhibit a strong narrow linewidth effect. Transmission electron microscopy studies revealed a cube-on-cube epitaxy with only a few twins depending on the annealing conditions. The low bitline resistance results in a linear drain voltage dependence of the programing characteristics and a suppression of secondary electron injection during programing.