Imaging deep holes in structures with gaseous secondary electron detection in the environmental scanning electron microscope

The environmental scanning electron microscope (ESEM) incorporates the functions of the conventional SEM while it has the added capability of allowing the examination of virtually any specimen in a gaseous environment. The main modes of imaging are all represented in the ESEM, and some developments with regard to the secondary electron (SE) mode are reported herewith.The conventional E-T detector fails to operate in the gaseous conditions of ESEM, but this obstacle has been overcome with the advent of a gaseous detection device (GDD). The principle of operation of this device is based on the monitoring of the products of interaction between signals and gas. Initially, the ionization from the signal/gas interaction was used to produce images of varying contrast and, later, the gaseous scintillation, from the same interaction, was also used to produce images. First, a low bias was applied to various electrodes but later a much higher bias was used for the purpose of achieving additional signal gain. By careful shaping and positioning the respective electrode, it was shown that SE imaging is possible in the ESEM. This has been also independently demonstrated by use of a special specimen preparation.

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Depletion layer imaging using a gaseous secondary electron detector in an environmental scanning electron microscope

Applied Physics Letters ◽

10.1063/1.124281 ◽

1999 ◽

Vol 75 (1) ◽

pp. 76-78 ◽

Cited By ~ 7

Author(s):

M. R. Phillips ◽

M. Toth ◽

D. Drouin

Keyword(s):

Electron Microscope ◽

Scanning Electron Microscope ◽

Secondary Electron ◽

Depletion Layer ◽

Environmental Scanning Electron Microscope ◽

Environmental Scanning ◽

Electron Detector ◽

Scanning Electron

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A New Mechanism for the Imaging of Crystal Structure in Non-Conductive Materials: An Application of Charge-Induced Contrast in the Environmental Scanning Electron Microscope (ESEM)

Microscopy and Microanalysis ◽

10.1017/s1431927600012873 ◽

1997 ◽

Vol 3 (S2) ◽

pp. 1197-1198 ◽

Cited By ~ 9

Author(s):

Brendan J. Griffin

Keyword(s):

Electron Microscope ◽

Scanning Electron Microscope ◽

Secondary Electron ◽

Secondary Emission ◽

Environmental Scanning Electron Microscope ◽

Electron Interaction ◽

Environmental Scanning ◽

Conductive Materials ◽

Scanning Electron ◽

Trapped Charge

The mechanism of the contrast in ‘environmental’ or ‘gaseous’ secondary electron images in the environmental scanning electron microscope is at best poorly understood. The original theory suggested a simple gas amplification model in which emitted secondary electrons ionise the chamber gas, leading to signal amplification and finally measurement at a biased detector. This theory is being advanced but little attention has as yet been paid to the factors which influence the actual secondary emission, although unusual contrast effects have been noted in one case. The conven-tional view is that the positive ion product of the gas-electron interaction results in charge neu-tralisation at the sample surface.The implantation and trapping of charge in non-conductive materials was recently described, in reference to electron range measurements. This work demonstrated that trapped charge influ-enced the secondary electron yield, with enhanced secondary electron emission above the region of trapped charge. The consequence is that the distribution of the trapped charge is seen as a bright circle on the surface of the specimen, centred on the point of beam exposure (Fig.l).

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Distribution and Behaviour of Positive Ions in the Environmental Scanning Electron Microscope (ESEM)

Microscopy and Microanalysis ◽

10.1017/s1431927600036370 ◽

2000 ◽

Vol 6 (S2) ◽

pp. 776-777 ◽

Cited By ~ 1

Author(s):

John P. Craven ◽

Frank S. Baker ◽

Bradley L. Thiel

Keyword(s):

Electron Microscope ◽

Scanning Electron Microscope ◽

Environmental Scanning Electron Microscope ◽

Environmental Scanning ◽

Positive Ions ◽

Electron Detection ◽

Gas Molecules ◽

Charged Ions ◽

Positively Charged ◽

Scanning Electron

Electron detection in the environmental scanning electron microscope relies upon the presence of a small pressure of a gaseous phase inside the microscope chamber. The presence of this gas controls two important mechanisms by which the microscope functions. The conventional gaseous secondary electron detector (GSED) applies a variable positive bias (0 to +600 V) directly above the specimen. Electrons ejected from the specimen surface due to the incident scanning probe are accelerated by this field towards the positively biased detector. Whilst traversing the gap between specimen and detector the electrons undergo ionizing collisions with gas molecules. These result in an amplification of the incident electron signal through the production of ejected ‘daughter’ electrons and leave behind positively charged ions. After production these ions are repelled by the detector bias and drift back towards the microscope stage where they aid charge neutralization on the surface of the specimen.

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