Scanning electron microscope and photomultiplier therefor and method of evaluating a sample

Abstract

A scanning electron microscope (SEM) configured to scan a sample by irradiating it with a plurality of source particles is provided. The SEM comprises a particle detector comprising a photomultiplier, the photomultiplier is configured to detect emitted particles from the sample and comprises a sensor surface having a plurality of cells each configured to detect one or more particles impinging thereon and to produce an output signal indicative of a quantity of impinging particles. The SEM further comprises a controller configured to define a plurality of zones each associated with one or more of the cells. The controller is further configured to calculate the magnitude of a triggering event based on the sum of output signals produced within a predetermined time interval by the cells within each of one or more of the zones. The geometry of the zones facilitates evaluating one or more properties of the sample.

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