Scanning Spreading Resistance Microscopy analysis of locally blocked implant sites

We describe a well-controlled experiment enabling the generation of multiple locally blocked implant sites within an integrated circuit in order to evaluate Scanning Spreading Resistance Microscopy (SSRM) as analysis method. Transistor gate structures with polycrystalline (poly-)Si material and source/drain regions were locally affected by lower implantation dose due to the presence of Polystyrene Latex (PSL) spheres on the wafer surface which have the effect of blocking the implantation process. These sites are initially characterised using in-line defect density inspection, SEM voltage contrast, Atomic Force Probe (AFP) current imaging and I(V) characterisation and then further analysed using Scanning Spreading Resistance Microscopy (SSRM). Subsequent analysis shows SSRM to be a very suitable and reproducible technique for visualisation of locally blocked implant sites in poly-Si gates. It is shown that the orientation of the prepared cross section is important for successful, artifact-free SSRM imaging. Our results demonstrate the potential of SSRM as a powerful analysis method for integrated device structures and set a reference system for topics like locally reduced poly-Si doping due to implant blocking or the presence of large poly-Si grains.

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