Edge Penetration Effects in the Low-Loss Electron Image in the SEM

1988 ◽  
Vol 46 ◽  
pp. 202-203
Author(s):  
Oliver C. Wells
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Beam Energy ◽  
Secondary Electron ◽  
Sharp Edge ◽  
Beam Diameter ◽  
Low Loss ◽  
Additional Information ◽  
Electron Image ◽  
Scanning Electron

The low-loss electron (LLE) image in the scanning electron microscope (SEM) is useful for the study of uncoated photoresist and some other poorly conducting specimens because it is less sensitive to specimen charging than is the secondary electron (SE) image. A second advantage can arise from a significant reduction in the width of the “penetration fringe” close to a sharp edge. Although both of these problems can also be solved by operating with a beam energy of about 1 keV, the LLE image has the advantage that it permits the use of a higher beam energy and therefore (for a given SEM) a smaller beam diameter. It is an additional attraction of the LLE image that it can be obtained simultaneously with the SE image, and this gives additional information in many cases. This paper shows the reduction in penetration effects given by the use of the LLE image.

scholarly journals Imaging of Shallow Surface Topography by the Low-Loss Electron (LLE) Method in the Scanning Electron Microscope

2002 ◽  
Vol 10 (6) ◽  
pp. 24-27
Author(s):  
Oliver C. Wells
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Surface Topography ◽  
Beam Energy ◽  
Secondary Electron ◽  
Low Loss ◽  
Information Depth ◽  
Sharp Edges ◽  
Scanning Electron

The low-loss electron (LLE) method in the scanning electron microscope (SEM) was proposed by Dennis McMullan in 1953: “…the beam from the specimen could be restricted to the electrons which have lost only small amounts of energy and which have therefore travelled only short distances through the specimen.”Subsequent studies showed that the LLE method gives different image contrasts from the more familiar secondary electron (SE) method: (i) it is less affected by specimen charging; (ii) has a shallower information depth for a given beam energy; (iii) shows less serious penetration effects at sharp edges; (iv) shows stronger channeling contrast; and (v) Is better for showing shallow surface topography.

Studies of poorly conducting samples by the low-loss electron method in the SEM

1994 ◽  
Vol 52 ◽  
pp. 1022-1023
Author(s):  
O. C. Wells ◽  
S. A. Rishton
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Beam Energy ◽  
Secondary Electron ◽  
Imaging Method ◽  
Tungsten Filament ◽  
Low Loss ◽  
Information Depth ◽  
Charging Current ◽  
Scanning Electron

The low-loss electron (LLE) image in the scanning electron microscope (SEM) shows stronger topographic contrast, less sensitivity to specimen charging and a shallower information depth in comparison with the more familiar secondary electron (SE) imaging method. When working with a poorly conducting or insulating sample the beam energy must be reduced to typically ~1.5 keV to minimise the net charging current at the surface of the specimen. Even if this is done correctly the topographic contrasts in the LLE image can still be considerably stronger than in the SE image.Fig. 1(a) shows the original LLE detector in which the sample is inclined at 45° to the electron beam. Fig. 1(b) shows a new detector which operates with a specimen tilt of 20°. Both have been used in a Cambridge Instrument Co. S250 Mk.III SEM.The possibility of obtaining a LLE image with a 20° specimen tilt is demonstrated with uncoated photoresist in Fig. 2 (tungsten filament) and with a “Crystal“ image store to capture and replay the image.

A Means to Overcome the Contrast Difficulties Inherent to Scanning Electron Microscopy

1970 ◽  
Vol 28 ◽  
pp. 394-395
Author(s):  
Arthur J. Saffir ◽  
Tyler A. Woolley ◽  
Nelson Yew
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Secondary Electron ◽  
Three Dimensional ◽  
Secondary Electrons ◽  
Conductive Coatings ◽  
Electron Image ◽  
Scanning Electron

The secondary electron image of the scanning electron microscope is similar to a light image of a three dimensional specimen. These two forms of "illumination", light and secondary electrons, have in common a contrast characteristic that makes photography or SEM micrography difficult. .. a tendency toward extreme highlights. The photographer encounters this phenomenon if his subject has a shiny surface, e.g., an automobile bumper. He overcomes this problem with dulling spray to suppress the undesirable highlights (reflections).This problem is also common in SEM studies, especially with biological specimens of poor conductivity. It is undesirable or impossible to subject thermolabile or living specimens to the deposition of conductive coatings.

Optimizing the collector solid angle for the low-loss electron image in the Scanning Electron Microscope

1987 ◽  
Vol 45 ◽  
pp. 548-549 ◽  
Author(s):  
Oliver C. Wells
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Solid Angle ◽  
Angle Of Incidence ◽  
Tungsten Filament ◽  
Low Loss ◽  
Backscattered Electrons ◽  
Glancing Angle ◽  
Electron Image ◽  
Scanning Electron

The low-loss electron (LLE) image in the scanning electron microscope (SEM) is formed by collecting backscattered electrons (BSE) that have lost less than a specified energy. Compared to the secondary electron (SE) image, these images are less affected by specimen charging and show the surface topography clearly when examining uncoated photoresist. However, LLE images sometimes contain dark shadows caused by the limited solid angle of the LLE detector. Here, we describe a way to position the sample (with a given LLE detector) so as to reduce these shadows as far as possible.The SEM was a Cambridge S-250 Mk. III with a tungsten filament. An experimental LLE detector was added. The SE image was obtained using the SE detector ordinarily present in the SEM.The LLE detector is shown in Fig. 1. The specimen is mounted close to the lens in the SEM with a glancing angle of incidence of 30°.

Charge Contrast Imaging (CCI): Revealing Enhanced Diagenetic Features of A Coquina Limestone

2016 ◽  
Vol 86 (6) ◽  
pp. 734-748 ◽  
Author(s):  
James O. Buckman ◽  
Patrick W.M. Corbett ◽  
Lauren Mitchell
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Lower Cretaceous ◽  
Secondary Electron ◽  
Contrast Imaging ◽  
Carbonate Cement ◽  
Additional Information ◽  
Backscattered Electron ◽  
Imaging Conditions ◽  
Scanning Electron

Abstract: Charge Contrast Imaging (CCI) is a low-vacuum scanning electron microscope (LV-SEM) technique that can be induced through partial surface charge suppression of uncoated nonconductive samples, imaged with a suitable detector such as a gaseous secondary electron detector (GSED). The technique commonly produces results similar in style to that of SEM-cathodoluminescence (SEM-CL), providing information on zoning, twinning, annealed fractures, and subtle chemical changes. The current work outlines an example from a Brazilian Lower Cretaceous coquina limestone, in which both optical and SEM-CL imaging produces a limited response from much of the sample. Backscattered electron (BSE) imaging typically suggests only a hint of the cement present, whereas CCI clearly displays a rich and varied cement stratigraphy. The earliest cement displays strong CCI, but appears mainly dark under CL imaging conditions (SEM-CL and optical CL). Later-stage manganese-“enriched” carbonate cement displays luminescence with both optical and SEM-CL, as well as a CCI response. Therefore CCI can provide additional information on cement zonation in an area where CL cannot.

Improved in-lens low-loss electron detector for the Scanning Electron Microscope

1991 ◽  
Vol 49 ◽  
pp. 480-481
Author(s):  
Oliver C. Wells ◽  
Eric Munro
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Beam Energy ◽  
High Field ◽  
Incident Beam ◽  
Objective Lens ◽  
Low Loss ◽  
Incident Beam Energy ◽  
The Magnetic Field ◽  
Scanning Electron

We have built an improved version of in-lens low-loss electron (LLE) detector for the scanning electron microscope (SEM) in which the LLE are energy-filtered by the focusing field. The sample is in the high-field region of a condenser-objective lens (Fig. 1). The fastest scattered electrons are then confined by the magnetic field of the lens into a region with a well-defined outer surface (Fig. 1(b)). A detector is moved under micrometer control to be just inside this surface. In this way, only the fastest scattered electrons (which are the LLE) are collected. In the earlier work, the detector was a flat aluminized garnet scintillator. This showed that the method did work but required that the incident beam energy E0 should be greater than the energy threshold of the scintillator.

Resolution of a Transmitted Electron Image Formed by A Scanning Electron Microscope

1970 ◽  
Vol 28 ◽  
pp. 386-387
Author(s):  
S. Takashima ◽  
H. Hashimoto ◽  
S. Kimoto
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Specimen Thickness ◽  
Probe Diameter ◽  
Transmission Electron ◽  
Electron Image ◽  
Conventional Transmission Electron Microscope ◽  
Scanning Electron

The resolution of a conventional transmission electron microscope (TEM) deteriorates as the specimen thickness increases, because chromatic aberration of the objective lens is caused by the energy loss of electrons). In the case of a scanning electron microscope (SEM), chromatic aberration does not exist as the restrictive factor for the resolution of the transmitted electron image, for the SEM has no imageforming lens. It is not sure, however, that the equal resolution to the probe diameter can be obtained in the case of a thick specimen. To study the relation between the specimen thickness and the resolution of the trans-mitted electron image obtained by the SEM, the following experiment was carried out.

Linewidth measurement using the low voltage SEM

1986 ◽  
Vol 44 ◽  
pp. 652-653
Author(s):  
M.G. Rosenfield
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Integrated Circuits ◽  
Secondary Electron ◽  
Low Voltage ◽  
Fabrication Process ◽  
Critical Dimensions ◽  
Linewidth Measurement ◽  
Threshold Technique ◽  
Scanning Electron

Minimum feature sizes in experimental integrated circuits are approaching 0.5 μm and below. During the fabrication process it is usually necessary to be able to non-destructively measure the critical dimensions in resist and after the various process steps. This can be accomplished using the low voltage SEM. Submicron linewidth measurement is typically done by manually measuring the SEM micrographs. Since it is desirable to make as many measurements as possible in the shortest period of time, it is important that this technique be automated.Linewidth measurement using the scanning electron microscope is not well understood. The basic intent is to measure the size of a structure from the secondary electron signal generated by that structure. Thus, it is important to understand how the actual dimension of the line being measured relates to the secondary electron signal. Since different features generate different signals, the same method of relating linewidth to signal cannot be used. For example, the peak to peak method may be used to accurately measure the linewidth of an isolated resist line; but, a threshold technique may be required for an isolated space in resist.

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