Metrology in a scanning electron microscope: theoretical developments and experimental validation

Abstract

A novel approach for correcting both spatial and drift distortions that are present in scanning electron microscope (SEM) images is described. Spatial distortion removal is performed using a methodology that employs a series of in-plane rigid body motions and a generated warping function. Drift distortion removal is performed using multiple, time-spaced images to extract the time-varying relative displacement field throughout the experiment. Results from numerical simulations clearly demonstrate that the correction procedures successfully remove both spatial and drift distortions. Specifically, in the absence of intensity noise the distortion removal methods consistently give excellent results with errors on the order of ±0.01 pixels. Results from the rigid body motion and tensile loading experiments at 200× indicate that, after correction for distortions, (a) the displacements have nearly random variability with a standard deviation of 0.02 pixels; (b) the measured strain fields are unbiased and in excellent agreement with previous full-field experimental data obtained with optical illumination; (c) the strain field variability is on the order of 60 microstrain in all components with a spatial resolution on the order of 25 pixels. Taken together, the analytical, computational and experimental studies clearly show that the correction procedures successfully remove both spatial and drift distortions while retaining excellent spatial resolution, confirming that the SEM-based method can be used for both micromaterial and nanomaterial characterization in either the elastic or elastic-plastic deformation regimes.

A Review of Surface Deformation and Strain Measurement Using Two-Dimensional Digital Image Correlation

“…In 1997, Sun et al [113] stated that the DIC technique was capable to measure the in-plane surface deformations at the magnification of up to 2000 pixels per millimetre. The DIC technique was further extended onto the study of Scanning Tunnelling Microscope (STM) images [28,114,115] and Scanning Electron Microscopy (SEM) images [116]. According to Jin et al [117], the mechanical properties of the electrodeposited nickel-based specimens at the micro-scale level were effectively determined with a combination of SEM imaging and DIC technique.…”

Toward Fast Calibration of Global Drift in Scanning Electron Microscopes with Respect to Time and Magnification

“…As a final step, the images are produced by detecting the emitted electrons using special electron detectors (Figure 1). Since the commercialization of SEM in the 1970s, it has become an essential tool in the study of nanomaterials and micronano systems, mainly because of its advantages in observation, analysis, and manipulation (Marchman, 1997;Sutton et al 2006;Charlot et al 2008;Kratochvil et al 2009;Tosello et al 2010;Arnoult et al 2010).…”

“…As a result, there is a shift in the image points w.r.t in their projection model, which in turn decomposes into drift and distortion (Maune 1976;Mizuno et al 1997;Santo et al 2002;Sutton et al 2006;Charlot et al 2008;Vignon et al 2001;Sinram et al 2002;Cornille, 2005;Mizuno et al 1997;Sicignano et al 2004). Most of these works address the calibration of the projection and the distortion, and has very little to do with the calibration of drift.…”

“…Most of these works address the calibration of the projection and the distortion, and has very little to do with the calibration of drift. According to Cornille (2005) and Sutton et al (2006Sutton et al ( , 2007 the pixel drift is estimated by the disparity between pairs of points and is fitted by B-splines w.r.t time. This model is used to estimate the drift and to remove it in real time.…”

Analysis of E-Beam Microlithography and SEM Imaging Distortions

“…Such spatially dense experimental information offers a wide scope of possibilities, such as for example the comparison with simulations to identify material parameters [1] associated with crystal plasticity constitutive equations [2]. Yet, the imaging distortions induced by the SEM electromagnetic environment should be taken into account to ensure the accuracy of the experimental information [3]. To perform kinematic measurements using Digital Image Correlation (DIC), a gray level pattern is required on the observed surface of the sample.…”