title: Comparison of Electron Imaging Modes for Dimensional Measurements in the Scanning Electron Microscope.
abstract: Dimensional measurements from secondary electron (SE) images were compared with those from backscattered electron (BSE) and low-loss electron (LLE) images. With the commonly used 50% threshold criterion, the lines consistently appeared larger in the SE images. As the images were acquired simultaneously by an instrument with the capability to operate detectors for both signals at the same time, the differences cannot be explained by the assumption that contamination or drift between images affected the SE, BSE, or LLE images differently. Simulations with JMONSEL, an electron microscope simulator, indicate that the nanometer-scale differences observed on this sample can be explained by the different convolution effects of a beam with finite size on signals with different symmetry (the SE signal's characteristic peak versus the BSE or LLE signal's characteristic step). This effect is too small to explain the >100 nm discrepancies that were observed in earlier work on different samples. Additional modeling indicates that those discrepancies can be explained by the much larger sidewall angles of the earlier samples, coupled with the different response of SE versus BSE/LLE profiles to such wall angles.
authors.affiliation: 1Engineering Physics Division,National Institute of Standards and Technology,100 Bureau Drive,MS 8120,Gaithersburg,MD 20899,USA.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Postek
authors.affiliation: 1Engineering Physics Division,National Institute of Standards and Technology,100 Bureau Drive,MS 8120,Gaithersburg,MD 20899,USA.
authors.forename: András E
authors.initials: AE
authors.lastname: Vladár
authors.affiliation: 1Engineering Physics Division,National Institute of Standards and Technology,100 Bureau Drive,MS 8120,Gaithersburg,MD 20899,USA.
authors.forename: John S
authors.initials: JS
authors.lastname: Villarrubia
authors.affiliation: 2Hitachi High Technologies America, Inc.,22610 Gateway Center Drive,Suite 100,Clarksburg,MD 20871,USA.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Muto
keywords: JMONSEL; backscattered electrons; electron beam modeling; low loss electrons; metrology; secondary electrons