Nano-Mapping of Vertical Contact Electrodes Using Synchrotron Scanning Photoelectron Microscopy

Abstract

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 finely focused X-ray beams, SPEM has demonstrated its suitability for investigating the electrical connectivity of individual contact holes at the nanoscale. In addition, we explore the potential enhancement of lateral resolution in SPEM mapping through advances in X-ray optics, positioning it as a valuable nanoscale inspection technique for advanced semiconductor manufacturing.

Keywords: Scanning photoelectron microscopy (SPEM), High aspect ratio contact hole, Nanoscale inspection methodology, Focused X-ray beam