An aberration measurement method for an objective lens in an electron microscope including an objective lens which focuses an electron beam that illuminates a specimen, and a detector which detects an electron beam having passed through the specimen, includes: introducing a coma aberration to the objective lens; measuring an aberration of the objective lens before introducing the coma aberration to the objective lens; measuring an aberration of the objective lens after introducing the coma aberration to the objective lens; and obtaining a position of an optical axis of the objective lens on a detector plane of the detector based on measurement results of the aberration of the objective lens before and after introducing the coma aberration.

In this invention, information of material composition, process conditions and candidates of crystal structure either known or imported from material database is used to determine sample stage tilt angle and working distance (WD). Under these determined tilt angle and WD, the intensity of the electrons emitted at different angles and with different energies is measured using a scanning electron microscope (SEM) system comprising: a use of materials database containing materials composition, formation process, crystal structure and its electron yield; a sample stage that is able to move, rotate and tilt; an processing section for calculating optimum working distance for an observation from material database and measurement condition; means for acquiring an image of crystal information of a desired area of a sample based on an image obtained from SEM observation.

A multi-beam charged particle microscope system, having a mirror mode of operation, can be operated to record a stack of images in a mirror imaging mode. The stack of images comprises at least two images of two different settings of at least on multi-aperture element, for example a focus stack, which allows the multi-beam charged particle microscope system to be inspected and recalibrated thoroughly. Related methods computer program products are disclosed.

A method of determining an energy spectrum or energy width of a charged particle beam (11) focused by a focusing lens (120) toward a sample plane (p.sub.S) in a charged particle beam imaging device is described. The method includes (a) introducing an energy-dependent deflection of the charged particle beam (11) that leads to a spot broadening along a dispersion axis in the sample plane (p.sub.S), and taking an image of a sample (10) arranged in the sample plane using the charged particle beam; (b) retrieving a beam profile of the charged particle beam from the image; and (c) determining the energy spectrum or energy width from the beam profile. Further embodiments described herein relate to a charged particle beam imaging device configured to determine the energy spectrum or energy width of a charged particle beam, particularly according to any of the methods described herein.

Disclosed are methods for sensing conditions of an electron microscope system and/or a specimen analyzed thereby. Also disclosed are sensor systems and electron microscope systems able to sense system conditions, and/or conditions of the specimen being analyzed by such systems. In one embodiment, a sparse dataset can be acquired from a random sub-sampling of the specimen by an electron beam probe of the electron microscope system. Instrument parameters, specimen characteristics, or both can be estimated from the sparse dataset.

The present disclosure is related to a Schottky thermal field (TFE) source for emitting an electron beam. Electron optics can adjust a shape of the electron beam before the electron beam impacts a scintillator screen. Thereafter, the scintillator screen generates an emission image in the form of light. An emission image can be adjusted and captured by a camera sensor in a camera at a desired magnification to create a final image of the Schottky TFE source's tip. The final image can be displayed and analyzed to for defects.

An assessment method comprising: using an assessment apparatus to generate assessment signals representing a property of a surface of a sample; processing the assessment signals to identify candidate defects and outputting a candidate defect signal; monitoring the status of the assessment apparatus for error conditions and generating a status signal indicating any error conditions during functioning of the assessment apparatus; and analysing the candidate defect signal to determine if the candidate defects are real defects; wherein analysis of a candidate defect is not completed if the status signal indicates that the assessment signal(s) and/or the candidate defect signal corresponding to the candidate defect would have been affected by an error condition.

A method of characterizing a fault in a scanning electron microscope, wherein the scanning electron microscope is suitable for analysing and/or processing a sample, especially a lithography mask, with the aid of an electron beam, wherein the method has the following steps: a) putting the scanning electron microscope in an equilibrium state, b) introducing a trigger event into the scanning electron microscope that disrupts the equilibrium state, c) detecting a response behaviour of the scanning electron microscope (100) to the trigger event, and d) comparing the response behaviour detected with an expected response behaviour for characterization of the fault.

A method of forming a multipole device (100) for influencing an electron beam (11) is provided. The method is carried out in an electron beam apparatus (200) that comprises an aperture body (110) having at least one aperture opening (112). The method comprises directing the electron beam (11) onto two or more surface portions of the aperture body (110) on two or more sides of the at least one aperture opening (112) to generate an electron beam-induced deposition pattern (120) configured to act as a multipole in a charged state, particularly configured to act as a quadrupole, a hexapole and/or an octupole. The electron beam-induced deposition pattern (120) can be an electron beam-induced carbon or carbonaceous pattern. Further provided are methods of influencing an electron beam in an electron beam apparatus, particularly with a multipole device as described herein. Further provided is a multipole device for influencing an electron beam in an electron beam apparatus in a predetermined manner.

A multi-beam particle microscope with a micro-optical unit for generating the multiplicity of individual beams is disclosed. The micro-optical unit comprises a mechanism for setting and maintaining an unchanging imaging property of the multiplicity of individual beams. In one example, the micro-optical unit comprises at least one measuring apparatus used to sense a change in length, a change in distance, a contamination or degradation of a component of the micro-optical unit during operation. A multi-beam particle microscope comprises a control unit which establishes an effect on at least one individual beam from a change in length, a change in distance, a contamination or degradation of the component. A multi-beam particle microscope also comprises a compensation element for compensating the effect on the at least one individual beam. According to a method for operating a multi-beam particle microscope, a remaining service life of the multi-beam particle microscope which meets a demand with respect to a wafer inspection is also established.