Design and Application of a Quadrupole Detector for Low‐Voltage Scanning Electron Microscopy

Abstract

Abstract Scanning electron microscopes operated at low voltages are applied in the inspection and metrology of microstructures as well as in the testing of integrated circuits. The efficiency of a conventional Everhart‐Thornley‐detector is poor in this application, especially if large samples, e.g. wafers, are inspected or tested at small working distances. In addition, the primary beam is deflected and aberrations are added by the extraction field of this detector. A new type of detector for secondary electron recording in low‐voltage scanning electron microscopy was, therefore, designed, built and tested. It utilizes crossed electric and magnetic quadrupoles to compensate for each other in their effect on the primary beam. On the other hand, both fields support the extraction and collection of the secondary electrons. During the test application, the detector showed high efficiency resulting in low‐noise images without any negative effect on the resolution.