Nano-mapping of vertical contact electrodes using synchrotron scanning photoelectron microscopy

With the rise in demand for high aspect ratio hole etching in semiconductor device fabrication, developing efficient inspection methods to detect etching failures is increasingly vital. Such failures can compromise the reliability of electrical connections of contact holes in highly sophisticated 3D semiconductor geometries. In this study, we present a nanoscale inspection technique employing synchrotron-based scanning photoelectron microscopy (SPEM) to assess the electrical connectivity of contact holes. Samples were systematically prepared with an array of contact holes of varying sizes. To simulate etching failure, a residual silicon oxide layer was deliberately left to induce the binding energy shift in photoelectron peak positions due to electrical charging. By obtaining W 4f and Si 2p spectra for the W-filled and W-unfilled structures, respectively, we objectively determined the electrical states of the contact holes. With its focused X-ray beams, SPEM has demonstrated its suitability for investigating the electrical connectivity of individual contact holes at the nanoscale. SPEM possesses the additional capability of non-destructive imaging the thickness of buried insulators inside an individual contact hole. Our results cast potential application of SPEM as a nanoscale inspection methodology for advanced semiconductor manufacturing.