Low-voltage, high-resolution scanning electron microscopy of polymers

1987 ◽  
Vol 45 ◽  
pp. 466-467 ◽  
Author(s):  
S. J. Krause ◽  
W.W. Adams ◽  
S. Kumar ◽  
T. Reilly ◽  
T. Suziki
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Voltage ◽  
Chromatic Aberration ◽  
Image Resolution ◽  
Resolution Limit ◽  
Crossover Point ◽  
New Generation ◽  
Beam Damage ◽  
Scanning Electron

Scanning electron microscopy (SEM) of polymers at routine operating voltages of 15 to 25 keV can lead to beam damage and sample image distortion due to charging. Imaging polymer samples with low accelerating voltages (0.1 to 2.0 keV), at or near the “crossover point”, can reduce beam damage, eliminate charging, and improve contrast of surface detail. However, at low voltage, beam brightness is reduced and image resolution is degraded due to chromatic aberration. A new generation of instruments has improved brightness at low voltages, but a typical SEM with a tungsten hairpin filament will have a resolution limit of about 100nm at 1keV. Recently, a new field emission gun (FEG) SEM, the Hitachi S900, was introduced with a reported resolution of 0.8nm at 30keV and 5nm at 1keV. In this research we are reporting the results of imaging coated and uncoated polymer samples at accelerating voltages between 1keV and 30keV in a tungsten hairpin SEM and in the Hitachi S900 FEG SEM.

Low-voltage Scanning Electron Microscopy of polymers

1986 ◽  
Vol 44 ◽  
pp. 676-677 ◽  
Author(s):  
O. W. Vaz ◽  
S. J. Krause
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Voltage ◽  
Polymer Surface ◽  
Image Distortion ◽  
Crossover Point ◽  
Voltage Scanning ◽  
Beam Damage ◽  
Scanning Electron

Scanning electron microscopy (SEM) of polymers at routine operating voltages of 15 to 25 keV can lead to beam damage and sample image distortion due to charging. These problems may be avoided by imaging polymer samples at a “crossover point”, which is located at low accelerating voltages (0.1 to 2.0 keV), where the number of electrons impinging on the sample are equal to the number of outgoing electrons emerging from the sample. This condition permits the polymer surface to remain electrically neutral and prevents image distortion due to “charging” effects. In this research we have examined Teflon (polytetrafluorethylene) samples and studied the effects of accelerating voltage and sample tilting on charging phenomena. We have also determined the approximate position of the “crossover point”.

LOW-VOLTAGE AND ULTRA-LOW-VOLTAGE SCANNING ELECTRON MICROSCOPY OF SEMICONDUCTOR SURFACES AND DEVICES

2002 ◽  
Vol 16 (28n29) ◽  
pp. 4387-4394 ◽  
Author(s):  
JINGYUE LIU
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Voltage ◽  
Image Resolution ◽  
Sem Images ◽  
Conducting Materials ◽  
Low Energies ◽  
Low Energy Electrons ◽  
Voltage Scanning ◽  
Scanning Electron

Low-voltage scanning electron microscopy (LV-SEM) enables us to directly examine non-conducting materials with high spatial resolution. Although use of ultra-low-energy electrons can provide further advantages for characterizing delicate samples, lens aberrations rapidly deteriorates the image resolution. The combined use of a retarding field and the probe-forming lens system can improve the image resolution for electrons with very low energies. In commercially available FEG-SEMs, the retarding field can simply be constructed by applying a negative potential to the specimen. Interesting contrast variations have been observed in ultra-low-voltage SEM images. In this short communication, we discuss the application of LV-SEM to examining semiconductor devices and also the recent development of the ultra-low-voltage SEM technique.

Low-Voltage Scanning Electron Microscopy in polymer characterization

1987 ◽  
Vol 45 ◽  
pp. 468-469 ◽  
Author(s):  
V. K. Berry
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Voltage ◽  
Polymer Surfaces ◽  
Conducting Materials ◽  
Theoretical Considerations ◽  
Voltage Scanning ◽  
Beam Damage ◽  
Scanning Electron

The application of low voltage scanning electron microscopy (LVSEM) to the characterization of polymers and non-conducting materials, other than semiconductors, has not been well explored yet. Some of the theoretical considerations and practical limitations which prevented the development of commercial instruments have mostly been addressed with the result that machines are now available which are optimized for low voltage (≥ 0.5 kV) operation. The advantages of working at low voltages are beginning to be recognized outside the semi-conductor industry. When we image uncoated polymer surfaces at low beam energies (0.5-1.5 kV), no beam damage or charging artifacts are experienced, because in this region the emitted electrons are equal to or more than the incident electrons and there is no deposition of charge underneath the surface due to the lower penetration of the incident electrons.

Surface effects in imaging uncoated polymers in low-voltage, high-resolution Scanning Electron Microscopy

1989 ◽  
Vol 47 ◽  
pp. 336-337
Author(s):  
S.J. Krause ◽  
W.W. Adams ◽  
D.C. Joy
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Resolution ◽  
Low Voltage ◽  
Polymer Surface ◽  
Beam Current ◽  
Image Features ◽  
20 Nm ◽  
New Generation ◽  
Scanning Electron

It has recently been shown that there are numerous advantages in imaging both coated and uncoated polymers in scanning electron microscopy (SEM) at low voltages (LV) from 0.5 to 2.0 keV compared to imaging at conventional voltages of 10 to 20 keV. The major disadvantages of LVSEM of degraded resolution and decreased beam current have been largely overcome with the new generation of field emission gun SEMs. In imaging metal coated polymers in LVSEM beam damage is reduced, contrast is improved, and charging from irregularly shaped features (which may be unevenly coated) is reduced or eliminated. Imaging uncoated polymers in LVSEM allows observation of the surface with little or no charging and with no alterations of surface features from the metal coating process required for higher voltage imaging. This is particularly important for high resolution (HR) studies of polymers where it is desired to image features 1 to 10 nm in size. Metal sputter coating techniques produce a 10 - 20 nm film that has its own texture which can obscure topographical features of the original polymer surface. In examining uncoated insulating samples at low voltages the effect of sample-beam interactions on image formation and resolution will differ significantly from the effect at higher accelerating voltages. In this study we discuss the nature of sample-beam interactions in uncoated polymers at low voltages and also present results on HRSEM of polymer samples which show some of these effects.

Recent developments in low-voltage SEM of polymers

1993 ◽  
Vol 51 ◽  
pp. 866-867
Author(s):  
S.J. Krause ◽  
W.W. Adams
Keyword(s):  
Low Voltage ◽  
Chromatic Aberration ◽  
Thermal Electron ◽  
Analytical Technique ◽  
Recent Developments ◽  
Beam Currents ◽  
New Generation ◽  
First Time ◽  
Voltage Scanning ◽  
Beam Damage

Over the past decade low voltage scanning electron microscopy (LVSEM) of polymers has evolved from an interesting curiosity to a powerful analytical technique. This development has been driven by improved instrumentation and in particular, reliable field emission gun (FEG) SEMs. The usefulness of LVSEM has also grown because of an improved theoretical and experimental understanding of sample-beam interactions and by advances in sample preparation and operating techniques. This paper will review progress in polymer LVSEM and present recent results and developments in the field.In the early 1980s a new generation of SEMs produced beam currents that were sufficient to allow imaging at low voltages from 5keV to 0.5 keV. Thus, for the first time, it became possible to routinely image uncoated polymers at voltages below their negative charging threshold, the "second crossover", E2 (Fig. 1). LVSEM also improved contrast and reduced beam damage in sputter metal coated polymers. Unfortunately, resolution was limited to a few tenths of a micron due to the low brightness and chromatic aberration of thermal electron emission sources.

Novel Approaches to Low-Voltage Scanning Electron Microscopy

1990 ◽  
Vol 48 (1) ◽  
pp. 366-367
Author(s):  
Arthur V. Jones
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Low Voltage ◽  
Electron Optics ◽  
Current Interest ◽  
New Concepts ◽  
Opportune Time ◽  
Novel Approaches ◽  
Voltage Scanning ◽  
Scanning Electron

In comparison with the developers of other forms of instrumentation, scanning electron microscope manufacturers are among the most conservative of people. New concepts usually must wait many years before being exploited commercially. The field emission gun, developed by Albert Crewe and his coworkers in 1968 is only now becoming widely available in commercial instruments, while the innovative lens designs of Mulvey are still waiting to be commercially exploited. The associated electronics is still in general based on operating procedures which have changed little since the original microscopes of Oatley and his co-workers.The current interest in low-voltage scanning electron microscopy will, if sub-nanometer resolution is to be obtained in a useable instrument, lead to fundamental changes in the design of the electron optics. Perhaps this is an opportune time to consider other fundamental changes in scanning electron microscopy instrumentation.

Imaging of polymer single crystals in low-voltage, high-resolution scanning electron microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 1106-1107
Author(s):  
W.W. Adams ◽  
G. Price ◽  
A. Krause
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Resolution ◽  
Single Crystals ◽  
Low Voltage ◽  
Polymer Surface ◽  
Beam Current ◽  
Image Features ◽  
First Results ◽  
Scanning Electron

It has been shown that there are numerous advantages in imaging both coated and uncoated polymers in scanning electron microscopy (SEM) at low voltages (LV) from 0.5 to 2.0 keV compared to imaging at conventional voltages of 10 to 20 keV. The disadvantages of LVSEM of degraded resolution and decreased beam current have been overcome with the new generation of field emission gun SEMs. In imaging metal coated polymers in LVSEM beam damage is reduced, contrast is improved, and charging from irregularly shaped features (which may be unevenly coated) is reduced or eliminated. Imaging uncoated polymers in LVSEM allows direct observation of the surface with little or no charging and with no alterations of surface features from the metal coating process required for higher voltage imaging. This is particularly important for high resolution (HR) studies of polymers where it is desired to image features 1 to 10 nm in size. Metal sputter coating techniques produce a 10 - 20 nm film that has its own texture which can obscure topographical features of the original polymer surface. In examining thin, uncoated insulating samples on a conducting substrate at low voltages the effect of sample-beam interactions on image formation and resolution will differ significantly from the effect at higher accelerating voltages. We discuss here sample-beam interactions in single crystals on conducting substrates at low voltages and also present the first results on HRSEM of single crystal morphologies which show some of these effects.

scholarly journals Low Voltage Scanning Electron Microscopy

2002 ◽  
Vol 10 (2) ◽  
pp. 22-23 ◽  
Author(s):  
David C Joy ◽  
Dale E Newbury
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Spatial Resolution ◽  
Low Voltage ◽  
Incident Beam ◽  
Operational Mode ◽  
X Ray ◽  
Rapid Fall ◽  
Voltage Scanning ◽  
Scanning Electron

Low Voltage Scanning Electron Microscopy (LVSEM), defined as operation in the energy range below 5 keV, has become perhaps the most important single operational mode of the SEM. This is because the LVSEM offers advantages in the imaging of surfaces, in the observation of poorly conducting and insulating materials, and for high spatial resolution X-ray microanalysis. These benefits all occur because a reduction in the energy Eo of the incident beam leads to a rapid fall in the range R of the electrons since R ∼k.E01.66. The reduction in the penetration of the beam has important consequences.

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