Magnetically filtered low-loss scanning electron microscopy

Abstract

The resolution of the scanning electron microscope can be improved by mounting the sample in the high-field region of a condenser-objective lens. Low-loss electrons (LLEs) are scattered from the sample with an energy loss of less than a few percent of the incident energy. In the past, LLEs have been collected with a retarding-field energy filter. A way has been found to collect LLEs using a detector located within the magnetic field of the condenser-objective lens which provides the required energy-filtering action. This greatly simplifies the apparatus and makes it possible to obtain LLE images with less tilt of the specimen and with a higher beam energy than before.

Low-Loss Electron Imaging for Enhanced Surface Detail in the Scanning Electron Microscope: The Contributions of Oliver C. Wells

“…Wells foresaw the need for a dedicated instrument. He and his colleagues developed a magnetically filtered low-loss detector [10, 30] located within the magnetic field of the condenser lens. Today, we are closer than ever to this goal.…”

Application of the low‐loss scanning electron microscope image to integrated circuit technology. Part II— chemically‐mechanically planarized samples

“…Thus, with a sample that is tilted by 60°from the horizontal, experiments with a moving LLE detector showed that the LLEs that conveyed topographic information were confined within about 30°of the plane of the surface (Wells and Bremer 1974). A cone with a semi-angle of 15°con-tains a solid angle of 0.214 sr (Fig.…”

“…Figure 9a shows a schematic drawing of such a detector with a curved input surface that conforms to the shape of this limiting surface. In the past, this method has been demonstrated with a tilted sample and with a single detector that was either a flat scintillator or a curved knife-edge that scattered the LLE onto a scintillator (Wells 1997;Wells et al 1990Wells et al , 1991Wells et al ,1992.…”

Imaging with surface sensitive backscattered electrons

“…[7][8][9] FSEI uses a high energy electron beam incident on a sample at a large tilt angle ͑Ͼ45°͒. Surface analysis at present is normally carried out by dedicated instruments in the disciplines of Auger electron spectroscopy, reflection high-energy electron diffraction, x-ray photoelectron spectroscopy, and transmission electron microscopy.…”