Measuring and controlling aberrations in electron microscopes

Abstract

An electron microscope system and a method of measuring an aberration of the electron microscope system are disclosed. An aperture filters an electron beam at a diffraction plane of the electron microscope to pass through electrons having a selected energy and momentum. A displacement of an image of the passed electrons is measured at a detector in an image plane of the electron microscope. An aberration coefficient of the electron microscope is determined from the measured displacement and at least one of the energy and momentum of the passed electrons. The measured aberration can be used toalter a parameter of the electron microscope or an optical element of the electron microscope to thereby control the overall aberration of the electron microscope.

Description

technical field [0001] The present invention relates generally to controlling aberrations in imaging devices, and more particularly to systems and methods for measuring and controlling the amount of aberrations in electron microscopes. Background technique [0002] Electron microscopes use a beam of accelerated electrons to irradiate a sample under test to obtain high-resolution images of the sample. Electron microscopes tend to suffer from certain aberrations, such as chromatic aberration, spherical aberration, etc., due to the multiple optical elements used to direct the electron beam and form an image of the sample. While these optics can be adjusted to account for aberrations, aberrations must first be measured before they can be resolved. Measuring spherical aberration and chromatic aberration in low-energy electron microscopy (LEEM) or photoelectron emission microscopy (PEEM) is a time-consuming process that is time-consuming and difficult to automate. In one method ...

AI Technical Summary

Problems solved by technology

To measure chromatic aberration, this method requires recalibrating the microscope for each energy setting, a tedious process

Also, none of these methods work when using optoelectronics

The difficulty of this testing procedure often limits the number of electron microscope calibrations

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