Detector optics for multiple electron beam test system

Abstract

A detector optics system for collecting secondary electrons (SEs) and/or backscattered electrons (BSEs) in a multiple charged particle beam test system is disclosed. Aspects of the detector optics system include: the ability to image and/or electrically test a number of locations simultaneously across the full width of a large substrate with high throughput and uniform collection efficiency while avoiding crosstalk between signals generated by neighboring beams. In one embodiment, a linear array of N electron beams causes SEs to be emitted from the substrate, which are then collected by one or more linear arrays of ≧2N detectors. Each linear array is connected to a signal combiner circuit which dynamically determines which detectors are collecting SEs generated by each electron beam as it scans across the substrate surface and then combines the signals from these detectors to form N simultaneous output signals (one per charged particle beam) for each detector array.