Charged particle microscope with improved electron detection

摘要

A method of investigating a flux of output electrons emanating from a sample in a charged-particle microscope, which flux is produced in response to irradiation of the sample by a beam of input charged particles, the method comprising the following steps: - Using a detector to intercept at least a portion of the flux so as to produce a set {I j } of pixeled images I j of at least part of the sample, whereby the cardinality of the set {I j } is M 1. - For each pixel p i in each image I j , determining the accumulated signal strength S ij , thus producing an associated set of signal strengths {S ij }. - Using the set {S ij } to calculate the following values: –ª An average signal strength S per pixel position i; –ª A variance à 2 S in S per pixel position i . - Using these values S and à 2 S to at least one map of said part of the sample, selected from the group comprising: –ª A first map, representing variation in energy of detected electrons as a function of position. –ª A second map, representing variation in number of detected electrons as a function of position. The set [I j } may be produced in different ways, such as: - By iteratively repeating a procedure whereby an entire n th image I n is captured before proceeding to capture an entire (n+1) th image I n+1 ; or - By iteratively repeating a procedure whereby, at an n th pixel position, a plurality M of different detector samples is collected before proceeding to an (n+1) th pixel position.