Towards sub-10 nm carrier profiling with spreading resistance techniques

Abstract

The manufacturing of state-of-the-art electronic devices involves an increasing demand for the accurate determination of ultra-shallow electrical carrier profiles related to the need to monitor the activation of the dopants with reduced thermal budgets. For sub-micron structures (down to 100nm) a qualified conventional spreading resistance probe system is an attractive tool for the reliable measurement of the resistivity (and carrier) depth variations in silicon due to its high geometrical resolution (nm) and high dynamic range (nine orders of magnitude). The spreading resistance (SR) roadmap for future process development (sub-50nm profiles), however, shows that there is a need for a significant reduction of the involved contact size and tip separation, a higher depth resolution (sub-nm) and an improved quantification. The recently introduced scanning spreading resistance microscopy technique resolves some of the involved issues such as the smaller contact size (20–50nm) and the higher geometrical depth resolution (sub-nm) when applied on a bevelled surface. Further developments are, however, needed in the fields of tip configuration, surface preparation and contact modelling to achieve timely all the needs of the SR roadmap. This is expected to lead to a new instrument, the NanoProfiler™, using two small (20–50nm contact size), closely spaced (250nm), conductive tips mounted on an atomic force microscope-based system. The NanoProfilerTM setup can easily achieve Angstrom depth resolution and therefore makes the profiling of sub-10nm structures feasible.