TiN scanning probes for electrical profiling of nanoelectronics device structures

Electrical atomic force microscopy (AFM) methods require highly conductive tips with nanometer-scale spatial resolution. Si tips with metal (e.g. PtIr) and doped-diamond coatings are most commonly used. Metal coatings are however prone to rapid wear and diamond coatings are limited in conductivity and spatial resolution. Therefore, we have developed solid TiN tips with a pyramidal shape made by molding using anisotropic Si etching for defining an inverted pyramid and TiN sputtering for mold filling. The TiN tips are attached to Ni electroplated cantilevers. The probes are removed from the substrate using a dedicated peel-off step. The fabrication process is based on state-of-the-art 200-mm Si wafer technology. Probe evaluation in AFM shows a typical spatial resolution of about 8–15 nm for these TiN tips. Using the hard TiN tips in scanning spreading resistance microscopy (SSRM) we demonstrate two-dimensional measurements of Ge doping staircase structures which could so far only be measured by doped diamond tips. Further measurements of carbon nanotube (CNT) interconnects and high-k metal gate stacks by conductive AFM (c-AFM) illustrate the potential of the TiN tips. This paper describes the probe concept, fabrication and evaluation in AFM.

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► We describe pyramidal TiN tips integrated into Ni cantilevers for electrical AFM.
► The probes are made by common 200-mm silicon wafer technology.
► The TiN tips withstand the high pressures (GPa range) needed for SSRM of Ge.
► SSRM of CNT interconnects and c-AFM of a high-k material is possible by TiN tips.