Ultra-high resolution SEMI-in-lens type FE-SEM, JSM-6320F, with strong magnetic-field lens with built-in secondary-electron detector

1994 ◽  
Vol 52 ◽  
pp. 484-485
Author(s):  
T. Miyokawa ◽  
H. Kazumori ◽  
S. Nakagawa ◽  
C. Nielsen
Keyword(s):  
High Resolution ◽  
Secondary Electron ◽  
Spherical Aberration ◽  
Incident Beam ◽  
Chromatic Aberration ◽  
Magnetic Flux Density ◽  
Objective Lens ◽  
Electron Detector ◽  
High Resolution Images ◽  
Working Distance

We have developed a strongly excited objective lens with a built-in secondary electron detector to provide ultra-high resolution images with high quality at low to medium accelerating voltages. The JSM-6320F is a scanning electron microscope (FE-SEM) equipped with this lens and an incident beam divergence angle control lens (ACL).The objective lens is so strongly excited as to have peak axial Magnetic flux density near the specimen surface (Fig. 1). Since the speciien is located below the objective lens, a large speciien can be accomodated. The working distance (WD) with respect to the accelerating voltage is limited due to the magnetic saturation of the lens (Fig.2). The aberrations of this lens are much smaller than those of a conventional one. The spherical aberration coefficient (Cs) is approximately 1/20 and the chromatic aberration coefficient (Cc) is 1/10. for accelerating voltages below 5kV. At the medium range of accelerating voltages (5∼15kV). Cs is 1/10 and Cc is 1/7. Typical values are Cs-1.lmm. Cc=l. 5mm at WD=2mm. and Cs=3.lmm. Cc=2.9 mm at WD=5mm. This makes the lens ideal for taking ultra-high resolution images at low to medium accelerating voltages.

Development of an Ultra - High - Resolution Low Voltage(LV) SEM with an Optimized “in-lens” Design

1990 ◽  
Vol 48 (1) ◽  
pp. 388-389
Author(s):  
Takashi Nagatani ◽  
Mitsugu Sato ◽  
Masako OSUMI
Keyword(s):  
High Resolution ◽  
Low Voltage ◽  
Collection Efficiency ◽  
Spherical Aberration ◽  
Chromatic Aberration ◽  
Spot Size ◽  
Objective Lens ◽  
Tilting Angle ◽  
Working Distance ◽  
Better Than

An “in-lens” type FESEM, Hitachi S-900, developed as an ultra high resolution SEM having 0.7nm resolution at 30kV(Nagatani et al 1986), was modified for better performance at low beam energy(about 5kV or below) with small aberrations of ths objective lens and dual specimen position design. This is in responce to the recent upsurge of interest in using the LVSEM, which enables us hopefully to observe the surface topography of uncoated samples directly with maximum fidelity(Pawley 1987).The actual visibility of the minute topographical details depends upon not anly the spot size of the scanning beam but also physics of interaction between impinging electrons and solid sample(Joy 1989). However, the resolution can never be better than the spot size. Then, it would seem logical to specify the spot size first when designing a high resolution SEM. As discussed earlier(Crewe 1985; Nagatani et al 1987), the spot size of the beam is mainly limited by spherical aberration of the objective lens and diffraction at high voltage(about 10 kV and above). On the other hand, chromatic aberration and diffraction are the dominant factors at low voltages(about 5kV or below). Source size of a cold field emission is so small that we could neglect it for simplicity.In general, chromatic aberration can be smaller at higher excitation of a narrow gap objective pole-piece, which also made the working distance short. Therefore, some compromise is necessary among minimized aberrations, required specimen size, stage traverse and tilting angle etc. In practice, tolerable distortion of the image at low magnification and collection efficiency of the secondary electrons are another factors to be considered in designing the instrument. By taking these factors in simulation, an optimized objective lens was designed as shown in Table 1.

Voltage-center COMA-free alignment for high-resolution Electron Microscopy

1994 ◽  
Vol 52 ◽  
pp. 410-411
Author(s):  
K. Ishizuka ◽  
K. Shirota
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Incident Beam ◽  
Chromatic Aberration ◽  
High Resolution Electron Microscopy ◽  
Beam Deflection ◽  
Objective Lens ◽  
Main Magnetic Field ◽  
Beam Direction ◽  
Resolution Electron

In a conventional alignment for high-resolution electron microscopy, the specimen point imaged at the viewing-screen center is made dispersion-free against a voltage fluctuation by adjusting the incident beam direction using the beam deflector. For high-resolution works the voltage-center alignment is important, since this alignment reduces the chromatic aberration. On the other hand, the coma-free alignment is also indispensable for high-resolution electron microscopy. This is because even a small misalignment of the incident beam direction induces wave aberrations and affects the appearance of high resolution electron micrographs. Some alignment procedures which cancel out the coma by changing the incident beam direction have been proposed. Most recently, the effect of a three-fold astigmatism on the coma-free alignment has been revealed, and new algorithms of coma-free alignment have been proposed.However, the voltage-center and the coma-free alignments as well as the current-center alignment in general do not coincide to each other because of beam deflection due to a leakage field within the objective lens, even if the main magnetic-field of the objective lens is rotationally symmetric. Since all the proposed procedures for the coma-free alignment also use the same beam deflector above the objective lens that is used for the voltage-center alignment, the coma-free alignment is only attained at the sacrifice of the voltage-center alignment.

Field Emission SEM with a Newly Developed FEGUN and Conical Strongly Excited Objective Lens

2000 ◽  
Vol 6 (S2) ◽  
pp. 764-765
Author(s):  
H. Kazumori ◽  
A. Yamada ◽  
M. Mita ◽  
T. Nokuo ◽  
M. Saito
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Scanning Electron Microscope ◽  
Secondary Electron ◽  
Objective Lens ◽  
Probe Current ◽  
Large Samples ◽  
Low Emission ◽  
Working Distance ◽  
Scanning Electron

A newly developed cold FE-GUN which enables to us to obtain large probe current and low emission noise, and conical strongly excited objective lens has been installed on the JSM-6700F Scanning Electron Microscope (SEM). In the range of accelerating voltages from 0.5 to 15kV, this instrument has got much better resolution as compared with in-lens type SEM (Ohyama et al 1986)(Fig. 1). We can obtain high-resolution secondary electron images with large samples (ex. 150mm ϕ×10mmH).Our old type objective lens (Kazumori et al 1994) has the limitation of working distance (WD), but the new lens enables us to work at very short WD at accelerating voltage of 15kV. As a result the spherical (Cs) and chromatic (Cc) aberration constants are 1.9mm and 1.7mm respectively at a WD of 3mm.In order to get large probe current, we increased emission current and got near the distance between the t ip of emi tter and the pr inciple plane of condenser lens.

Current and future aberration correctors for the improvement of resolution in electron microscopy

2009 ◽  
Vol 367 (1903) ◽  
pp. 3665-3682 ◽  
Author(s):  
M. Haider ◽  
P. Hartel ◽  
H. Müller ◽  
S. Uhlemann ◽  
J. Zach
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Low Voltage ◽  
Spherical Aberration ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Voltage Electron ◽  
System A ◽  
Transmission Electron ◽  
Correction System

The achievable resolution of a modern transmission electron microscope (TEM) is mainly limited by the inherent aberrations of the objective lens. Hence, one major goal over the past decade has been the development of aberration correctors to compensate the spherical aberration. Such a correction system is now available and it is possible to improve the resolution with this corrector. When high resolution in a TEM is required, one important parameter, the field of view, also has to be considered. In addition, especially for the large cameras now available, the compensation of off-axial aberrations is also an important task. A correction system to compensate the spherical aberration and the off-axial coma is under development. The next step to follow towards ultra-high resolution will be a correction system to compensate the chromatic aberration. With such a correction system, a new area will be opened for applications for which the chromatic aberration defines the achievable resolution, even if the spherical aberration is corrected. This is the case, for example, for low-voltage electron microscopy (EM) for the investigation of beam-sensitive materials, for dynamic EM or for in-situ EM.

Information limit of a 300kV field emission TEM

1995 ◽  
Vol 53 ◽  
pp. 588-589
Author(s):  
I. Ishikawa ◽  
K. Kaneyama ◽  
T. Tomita ◽  
T. Honda ◽  
M. Kersker
Keyword(s):  
Thin Film ◽  
High Resolution ◽  
Phase Contrast ◽  
Zero Point ◽  
Chromatic Aberration ◽  
Energy Spread ◽  
Electron Gun ◽  
Objective Lens ◽  
Small Energy ◽  
High Resolution Images

The use of an FEG on a high resolution microscope will increases the spacial and temporal coherence of the microscope due to the improvement in coherence of the electron source. Additionally, the improved energy spread will extend the envelope of the phase contrast transfer well beyond the first zero point at Sherzer focus. Between the Sherzer point and the ultimate point of zero contrast (the information limit) there is useful information for the analysis of high-resolution images. We have already obtained a resolution of 0.194nm and an information limit of 0.14nm by using the 200kV FETEM (JEM-2010F). In the present experiment, we attempted to obtain a higher resolution and information limit by using the 300kV FE TEM (JEM-3000F).The electron gun is configured with a ZrO/W Shottky emitter which has a small energy spread with a stable emission. The objective lens has a spherical and chromatic aberration of 0.6mm and 1.3mm respectively. The specimen used was gold islands on an amorphous Ge thin film.

Design of an Objective Lens with Minimum Chromatic Aberration Coefficient

1997 ◽  
Vol 3 (S2) ◽  
pp. 1083-1084
Author(s):  
K. Tsuno ◽  
D. A. Jefferson
Keyword(s):  
Magnetic Flux ◽  
Spatial Frequency ◽  
High Voltage ◽  
Spherical Aberration ◽  
Wave Length ◽  
Finite Size ◽  
Chromatic Aberration ◽  
Magnetic Flux Density ◽  
Objective Lens ◽  
Pole Piece

The Schelzer resolution is defined as the highest spatial frequency which is transferred into the image with the same phase as all lower frequencies. The resolution of the information limit is, however, determined by the information from the specimen which is equal to the degree of noise. The Schelzer resolution is determined by the wave length and the spherical aberration coefficient Cs of the objective lens. It reached 0.1 nm at 1250 kV. The limit of the resolution has been calculated numerically and it is written as d = 4.65(BsVr)−1/4 (nm), where Bs (in T) is the saturation magnetic flux density of the pole-piece material and Vr the relativistically corrected accelerating voltage. The resolution of the information limit is determined by the axial chromatic aberration coefficient Cc and incoherent effects such as the finite size of the source, beam divergence, energy spread, instabilities of the high voltage and lens current. The limit of the resolution is not clear. Most of the objective lenses of commercial microscopes are designed to optimize Cs rather than Cc. In this investigation, however, we describe the limit of Cc for 200 kV microscopes.

A field-emission SEM optimized for operation at low beam voltage

1993 ◽  
Vol 51 ◽  
pp. 630-631
Author(s):  
JB Pawley ◽  
J Ximen ◽  
PS-D Lin ◽  
M. Schippert
Keyword(s):  
High Resolution ◽  
Radiation Damage ◽  
Field Emission ◽  
Secondary Electron ◽  
Structural Features ◽  
Objective Lens ◽  
Beam Diameter ◽  
Beam Voltage ◽  
High Resolution Images ◽  
Topographic Imaging

The advantages of operating the SEM at low beam voltage (V0 ) have been recognized for some time. They include: less specimen charging, greater contrast in the fine topographic component of the secondary electron (SE) signal and reduced radiation damage. Although initially it was difficult to obtain high resolution images when using low V0, this limitation can be essentially overcome by employing both a FE source and an immersion objective lens. In an instrument employing both of these features it is possible to produce a beam diameter of about 3 nm @ 1.5 kV. When insulating specimens are viewed under these conditions, the resolution in the image is limited more by the structure of the coating material than by the beam diameter, while on conductors, small structural features produce useful contrast only at low V0.The remaining obstacle to more widespread use of LVSEM for high resolution topographic imaging is the high cost of the equipment.

Single-Pole Objective Lens for Low-Voltage SEM High Resolution Wafer Observation

1990 ◽  
Vol 48 (1) ◽  
pp. 396-397
Author(s):  
Akira Yonezawa ◽  
Yukio Takeuchi ◽  
Takeshi Kano ◽  
Hiroshi Ishijima
Keyword(s):  
High Resolution ◽  
Secondary Electron ◽  
Low Voltage ◽  
Objective Lens ◽  
Magnetic Lens ◽  
Large Size ◽  
Specimen Holder ◽  
Electron Image ◽  
Working Distance ◽  
Etch Residue

The low-voltage in-lens FE-SEM can observe a 10nm diameter pinhole on Si polycrystal film and etch residue which cannot be observed by a typical SEM. However,this in-lens SEM cannot observe a large size specimen such as a wafer. A new single pole objective lens was recently designed for this purpose. Because of the small bore diameter (2∼3mm),when using this lens,a negative potential must be given to the specimen holder to improve the efficiency of the secondary electron detection.From researching of a single pole magnetic lens system used for observing a wafer with high resolution, we obtained the secondary electron image. Fig.1 shows the single pole objective lens mounted on the specimen chamber. L is the distance between the pole face and the opposite iron wall,R is the radius of the outer yoke,and WD is the working distance. The design features are as follows:

Development of a Computer-Controlled 120kV High-Performance Tem

1996 ◽  
Vol 54 ◽  
pp. 446-447
Author(s):  
H. Kobayashi ◽  
I. Nagaoki ◽  
E. Nakazawa ◽  
T. Kamino
Keyword(s):  
High Resolution ◽  
High Performance ◽  
Spherical Aberration ◽  
Focal Length ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Wide Field ◽  
High Contrast ◽  
Computer Controlled ◽  
The Magnetic Field

A new computer controlled 120kV high performance TEM has been developed(Fig. 1). The image formation system of the microscope enables us to observe high resolution, wide field,and high contrast without replacing the objective lens pole-piece. The objective lens is designed for high- contrast (HC) and high-resolution(HR) modes, and consists of a double gap and two coils. A schematic drawing of the objective lens and the strength of the magnetic field of the lens is described in Fig.2. When the objective lens is used in HC mode, upper and lower coils are operated at a lens current of same polarity to form the long focal length. The focal length(fo), spherical aberration coefficient(Cs) and chromatic aberration coefficient (Cc) in HC mode at 100kV are 6.5, 3.4 and 3.1mm, respectively. Magnification range at HC mode is × 700 to × 200,000. The viewing area with an objective aperture of a diameter of 10μm is 160mm in diameter. In HR mode, the polarity of lower coil current is reversed to form a shorter focal length for high resolution image observation. The fo, Cs and Cc of the objective lens in HR mode at lOOkV are 3.1, 2.8 and 2.3mm, respectively. The highest magnification in HR mode is × 600,000.

High Resolution Side-Entry Goniometer

1980 ◽  
Vol 38 ◽  
pp. 56-57
Author(s):  
T. Honda ◽  
H. Watanabe ◽  
K. Ohi ◽  
E. Watanabe ◽  
Y. Kokubo
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
High Resolution ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Resolution Limit ◽  
Tilting Angle ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
High Resolution Images

An analytical electron microscope equipped with a side-entry goniometer (SEG) has recently become more widespread than a conventional electron microscope by the following reasons: (1) a variety of specimen holders, (2) large tilting angle with eucentricity. However, the resolution of SEG-system is about 0.4 nm, whereas the resolution of 0.25 nm or less can be obtained by an electron microscope equipped with a top-entry goniometer (TEG)1). Factors determining the resolution of an electron microscope are (1) the aberration coefficients of the objective lens, (2) stability of exciting currents, (3) illumination angle of the electron beam on the specimen, (4) energy spread of the electron beam, and ( 5) vibration and specimen drift. It has been usually difficult to observe high resolution images during use of the SEG system, because of the aberration coefficients of the objective lens, vibration and specimen drift. In order to obtain a resolution of less than 0.3 nm with SEG system at 200 kV, both of spherical and chromatic aberration coefficients should be reduced less than 2 mm. Moreover, relative amplitude of vibration between the specimen and pole pieces should be less than a half value of resolution limit. The image drift should be less than 0.02 nm/sec, because the exposure time usually required for photographing a high resolution image is about 5 second.

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