TEM image acquisition is subject to limitations in resolution imposed by the physics of the position-sensitive detection process. in existing on-line digital cameras detection consists of scintillation, image transfer and photon detection by a CCD. Scintillator resolution is governed primarily by the incident beam energy. Material parameters affect the resolution only weakly. Some improvement can be made with a thin transmission scintillator. Still, backscatter of electrons from below can form a noisy background. Optical transfer resolution also has an important effect on overall camera system resolution. Leakage of light within scintillator, between fibers, at interfaces, and the inherent resolution loss due to binning into a finite pixel all contribute to optical resolution loss. This point spread function is narrower than the electron point spread function above 100kV but has an affect at all voltages. Long-range light leakage (psf tail) affects the background noise in diffraction work where there is often a 10e6 ratio between central peak and diffraction spot of interest. Thus, the number of resolved pixels in a TEM image detector is limited by the area of the detector, the effective thickness of the scintillator and the quality of the image transfer.

Gatan has developed several improvements which will address both electron and lightoptical resolution loss.

A unique in situ nanoindentation stage has been built and developed at the National Center for Electron Microscopy in Berkeley, CA. By using piezoceramic actuators to finely position a 3-sided, boron-doped diamond indenter, we are able to image in real time the nanoindentation induced deformation of thin films. Recent work has included the force-calibration of the indenter, using silicon cantilevers to establish a relationship between the voltage applied to the piezoactuators, the displacement of the diamond tip, and the force generated.

In this work, we present real time, in situ TEM observations of the plastic deformation of Al thin films grown on top of lithographically-prepared silicon substrates. The in situ nanoindentations require a unique sample geometry (see Figure 1) in which the indenter approaches the specimen normal to the electron beam. in order to meet this requirement, special wedge-shaped silicon samples were designed and microfabricated so that the tip of the wedge is sharp enough to be electron transparent.

Recently several different methods have been proposed to reconstruct the projected crystal potential from electron diffraction patterns. These methods envolve either diffraction patterns at many different orientations (as many orientations as beams in the pattern) and/or images, which makes their experimental realization difficult. We propose an entirely new method for reconstructing the projected crystal potential from fully dynamical [including absorption and multiple scattering effects to all orders] diffraction patterns from only a single crystal orientation and no image at all. Knowledge of the specimen thickness is not necessary. However, it requires diffraction patterns at many different accelarating voltages, which is a parameter that can easily be varied (within a certain range) in most modern electron microscopes. Since the intensities in the electron diffraction pattern are not affected by lens abberations this method is capable of reconstructing the projected potential with a resolution far better than that of any method using HRTEM images.

Two optimum defocus conditions are well known to users of high-resolution transmission electron microscopes. Scherzer defocus is useful in high-resolution electron microscopy (HREM) because it produces an image of the specimen “projected potential” to the resolution of the microscope. Lichte defocus is useful in electron holography because it optimizes sampling in frequency-space by minimizing the slope of the microscope objective lens phase change out to the highest spatial frequency in the hologram, consequently minimizing dispersion. For focal-series reconstruction, the requirement to maximize transfer into the image of high-frequency diffracted beam amplitudes leads to a third optimum defocus condition.

Image reconstruction methods allow the achievement of super-resolution - resolution beyond the native (Scherzer) resolution of the microscope - by correction of the phase changes introduced by the microscope objective lens. One such method is focal-series reconstruction, in which diffracted-beam information obtained at several different focus values is combined. to produce a valid super-resolution result, it is necessary to ensure that every spatial frequency is represented appropriately. Suitable choice of an optimum defocus produces optimum transfer of diffracted-beam amplitudes at any chosen spatial frequency.

We developed a 1-MV field-emission transmission electron microscope to help in further improving electron holography, Lorentz microscopy, and high-resolution electron microscopy. This microscope is characterized by an electron beam having the highest brightness ever, 2×1010 A/cm2, and by the highest lattice-resolution below 0.5 Å. These two features were attained by minimizing the mechanical vibration of the whole column and by improving the stability of both the electron beam and the high voltage. If the tiny electron source located at the top of the 7-m-high microscope moves by as little as a fraction of the source size, 50 Å in diameter relative to the column, due to mechanical vibration or beam deflection by the AC magnetic fields, the beam brightness will be greatly degraded. If the ripples ΔE of the high-voltage E exceed ΔE/E = 5 × 10−7 /min, then the inherent monochromatic feature of the beam is deteriorated by the increase in energy spread.

Through the preliminary experiments testing the vibration and magnetic shielding of the acceleration tube as well as the high stability of the high voltage, and through the numerical simulations on the vibration modes of the whole column, we were led to the conclusion that the microscope must be separated into three parts that are connected by cables.

Ultrahigh-vacuum transmission electron microscopy (UHVTEM) has become increasingly popular for the direct observation of nanostructures having clean surfaces, since industrial requirements to make and research nano-scale materials have been rapidly growing for quantum or nanoscale electronic devices. Since we have first developed high resolution UHVTEM in 1986, the UHVTEMs have been evolved with steady advances such as UHV compatible goniometer, field emission gun or etc. Furthermore, the UHVTEM started to combine analytical capabilities such as energy dispersive X-ray spectrometer, in-column type energy filter and etc., and to combine STM (scanning tunneling microscope). The UHV technology is essential for the analysis, because the portion of contaminant in a nano-scale specimen increases as the size of the specimen goes down. This paper reports the results of gold nanostructures by recently the developed UHVTEM.

Figure 1 shows recently developed UHVTEM with Schottky type field emission gun.

The attainable information in transmission electron microscopes is limited today primarily by chromatic aberrations, because the new generation of spherical aberration correctors has practically eliminated resolution limits caused by spherical aberration. If it would be possible to develop an electron source with 0.2 eV energy width, the limitations of chromatic aberrations could be minimized, and techniques like Electron Energy Loss Spectroscopy (EELS) could provide much more detail on the type of bonding between atoms. At present, the main approach to reduce the energy width of present day field emission electron sources is to incorporate a beam monochromator in the electron gun. The challenge for such a monochromator is not only to provide a small energy width of 0.2 eV or less, but also to preserve the brightness of the gun as much as possible at a level of current sufficient for high resolution imaging on a routine basis.

Over the last few years, several different designs for monochromators have been proposed. All designs are based on energy dispersive components which separate electrons of different energies spatially and eliminate the ones with high energy deviation by means of a selection slit.

The strong technological trend towards higher and higher integrated systems is resulting in considerably increasing demands on nanotechnique and -electronics. One of the most important sets of information is the characterization of the inner interfaces within such materials not only concerning the atomic structure but also concerning chemical composition and bonding and concerning local strain. New generation energy filtering TEMs using corrected in-column spectrometers and providing considerably increased power of resolution concerning imaging and analysis are thus essential in order to be able to understand, define, built and characterize such devices.

Within the SESAMe (Sub-eV-sub-Angstrom Microscope) [1] project, LEO and CEOS realize such a microscope for the MPI of Metal Research, Stuttgart in 3 steps. For step 1 and 2 an in second order completely corrected and in third order minimized 90° OMEGA energy filter has been developed. This filter is operating since one year in a 200 kV LEO EFTEM with LaB6 emitter (Step 1) [4]. Results will be presented by W. Sigle during this meeting. This filter will also be incorporated in the Sub-Angstrom-TEM (SATEM) with Cs corrector for the Research Center Jülich.

The potential utility of FIB for routine (and novel) applications has come to forefront recently due to advances in ion optics which now allow formation of focused ion probe of better than ∼10-20 nm containing current density exceeding several A/cm2, with a liquid metal source (typically Gallium). The small ion probe size, coupled with shallow sputtering depth - yet high sputtering yield of ions, has opened several opportunities in machining, lithography and ion-assisted deposition.[1-3] These developments, including automation, multi-specimen stages, cross-compatible specimen holders for FIB/TEM/SEM, use of in-situ electron beam (so-called dual beam), coupled with innovations such as the “lift-off” process[4], have provided an invaluable set of tools for microelectronic defect characterization. However, re-deposition (contamination), ion implantation/damage especially for desirable thinner sections (<∼50 nm) remain major concerns for further applications.

While much of the excitement in TEM community for FIB is due to thin foil specimen preparation (especially in microelectronics), we have been exploiting the site-specific micromachining aspect of FIB beyond specimen preparation for TEM, which is the focus of this contribution. Two broad themes will be presented: One exploits the site-specificity of FIB in making thin sections (including lift-off) at and across localized deformation as in indentation response of micro/nanocomposites. The other involves FIB as a fabrication tool for sputtering/drilling arbitrary shapes and sizes down to 20-50 nm, to enhance functional aspects.

Recent developments in FIB have included optics and automation improvements as well as technique development. in the past decade, ion beam optics have improved rapidly to the point where the beam size and profile does not dramatically limit its use in many applications ranging from failure analysis to manufacturing. Developments in FIB can therefore focus on techniques to increase removal rates, enhance selectivity and improve surface finish. in this work we present various efforts to improve FIB micromachining using chemical enhancement, where the incident ions initiate chemical reactions with surface adsorbates; and using geometrical optimization of milling patterns. Chemical enhanced FIB micromachining (CE-FIBM) techniques include the use of water vapor to improve FIB micromachining of various materials including polymers, integrated circuits and diamond as well as the use of various halogen based (F, Cl and I) precursors for machining of materials ranging from Si to Fe-Ni alloys. The machining of a free edge provides a geometrical yield enhancement of more than 5 and, when combined with simultaneous chemical enhancement, can increase total yield by as much as 30 times. The major applications of FIB for preparing cross sectional analysis samples for FIB or SEM imaging, or for TEM analysis benefit in may ways from the specialized gas chemistry assistance methods developed over the past 10 years. Integrated circuit and MEMS device editing techniques have also been enhanced through the use of unique materials specific gas assisted FIB solutions.

Segregation of elements to the grain boundaries in Ni-base alloys can have a large effect on the mechanical and corrosion properties of these materials. The extent of segregation, whether it is equilibrium or non-equilibrium segregation, is dependent upon the thermo-mechanical treatments applied to the alloy. in order to determine if a particular thermo-mechanical process delivers the desired microstructure, a complete microstructural analysis including an examination of grain boundary segregation must be performed.

In the past, TEM has been used to identify the various phases and precipitates in these materials through the use of bright- and dark-field imaging, electron diffraction, and EDS. However, one of the elements that can play a large role in determining the properties of these alloys is boron. in this group of alloys, boron is generally present in bulk analyses in only a few tens of ppm, and as a result it is difficult to detect using the aforementioned techniques. More commonly, boron segregation to the grain boundaries is usually studied by means of Auger analysis, whereby the sample is charged with hydrogen in order to promote brittle intergranular fracture in-situ in the Auger microprobe. Boron can then be detected at the surface of the clean grain boundary fracture surfaces.

Recent developments in transmission electron microscopy put high demands on specimen preparation. in general the imaging quality is not limited by the performance of the microscope but by the quality of the specimen. in order to achieve a spatial resolution of 0.1 nm in HRTEM undamaged samples with a thickness below 10 nm are required. in energy filtering analytical electron microscopy (EFTEM), a constant specimen thickness over large areas and very low contamination is needed.

Conventional ion-milling techniques for TEM specimen preparation are essentially blind. Thus, it is left to chance whether the specimen detail of interest is suitable for TEM-imaging (many specimen areas are too thick). Another problem is the reaction of the specimen with the atmosphere during the transfer from the preparation stage to the microscope, which makes it very difficult to obtain the clean specimen surfaces that are needed in analytical EFTEM. Especially in high-resolution electron microscopy and electron holography the formation of amorphous oxidation and contamination layers on otherwise crystalline materials may seriously reduce the quality of high resolution images of the crystal structure.

As the importance of nano-scaled structures in both science and engineering increases, techniques for reconstructing three-dimensional structural, crystallographic and chemical relationships become increasingly important. in this paper we described a technique which uses focused ion beam (FIB) sputtering to expose successive layers of a 3D sample, coupled with secondary electron imaging and secondary ion mass spectrometry of each sputtered surface. Computer interpolation of these different slice images then enables reconstruction of the 3D structure and chemistry of the sample. These techniques are applicable to almost any inorganic material, at a spatial resolution of tens of nanometers, and fields of view up to (tens of μm).

The FIB instrument used in this study is an FEI 200 with a minimum ion probe diameter < 10 nm, an ion current density ∼ 10 A/cm2, a maximum ion current of 11 nA, and a standard Ga+ ion energy of 30 keV. Our instrument is equipped with a continuous dynode electron multiplies (CDEM) for secondary electron imaging and a quadrupole mass spectrometer for secondary ion mass spectroscopy (SIMS) / element specific mapping. Gallium ions of this energy will ablate any material, with sputter yields typically of order ten, corresponding to a material removal rate of order 1 μm3nA−1s−1.

Techniques for the 3D analysis of materials at the sub-micron level are of major importance for understanding the structure and performance of new nanoengineered materials. Established techniques for determining 3D shapes of individual grains include X-ray tomography and light microscopy for grains ≫ 1μm, and 3D-atom probe for conducting grains < 50nm size. A new technique of TEM EELS tomography is being developed for particles 2-300nm in a chemically distinct matrix.

For the grain size range 200nm-20μm, we have applied a new technique of 3D analysis using focused ion beam (FIB) sectioning to the site-specific analysis of the shape of individual grains in a single phase matrix. in the 3D FIB technique, a sample surface may be serially sectioned using a highly focused beam of Ga+ ions (Fig. 1). A sequential set of 2D secondary electron images through the sample can be aligned in 3D by cross-correlation of the position of reference markers in the 2D images.

We have developed an FIB micro-sampling technique to prepare both plan view and cross-sectional TEM specimens from a specific site.

The instruments that were used in this study are the Hitachi FB-2000A FIB system equipped a with micromanipulator unit and an HF-2200 cold field emission 200kV analytical TEM equipped with a scanning attachment allowing both STEM and SEM imaging.

Figure 1 shows a procedure to prepare a micro-sample for either plan view or cross-sectional TEM observation of the specific site. First, the micro-sample for plan view TEM observation is trench milled by using an FIB(Figure 1a). Second, a tip of a micromanipulator W-probe is bonded to the micro-sample with the FIB assisted metal deposition. Then, the micro-sample is lifted out and transferred onto a micro-sample carrier(Figure 1b).

Advantages of the FIB lift-out technique over traditional H-bar TEM specimen preparation have been recognized. The ability to rapidly (< 1 hour) prepare a site specific TEM specimen without destroying the entire bulk specimen has led to a wide spread reliance on this method. The main disadvantage of this technique is an inability to accomplish additional membrane thinning if required. Traditional H-bar preparation allows additional thinning. However, mechanical polishing is time consuming and the bulk sample is destroyed. A method has been developed which combines the efficient, site specific advantages of the lift-out method with the H-bar's ability to accomplish additional thinning. in this procedure a lift-out specimen is removed from the bulk sample and mounted onto a half-grid in a configuration similar to that employed by the H-bar technique.

A 1.0-micron thick lift-out specimen was prepared using a FEI Strata DB-235 FIB dual-beam workstation by sputtering away bulk material leaving a thin membrane containing a desired feature (FIG 1).

The FIB lift-out (LO) technique has been applied to a sample that been pulled to failure by tensile testing. An aluminum alloy (5083) was cold deformed using DSI's Maxistrain technology [1]. The alloy was cut with a low speed diamond coated wafering blade such that the fracture surface would fit inside the focused ion beam (FIB) specimen chamber. The sample was then mounted and placed in an FEI 200TEM FIB instrument. An FIB image of the tip of the fracture surface is shown in figure 1. A region for TEM specimen preparation was chosen such that the specimen would be in the plane of the tensile axis. The area of interest was chosen to ensure that FIB undercutting of the specimen could be accomplished upon tilting inside the FIB, and to ensure that the micromanipulator needle would have access to the FIB prepared specimen. A region of interest was coated with Pt using the FIB. A TEM specimen was then prepared in the usual LO manner [2,3]. The location of the finished LO specimen is circled in figure 1. After FIB milling was completed, the sample was removed from the FIB and placed on a light optical microscope stage. The electron transparent membrane was removed from the deformed sample using a glass rod attached to a micromanipulator. While the successful LO was performed, it should be noted that the micromanipulation was non-trivial due to the rough fracture surface combined with the poor depth of field of the light optical microscope.

In this communication we present a method using Focused Ion Beam (FIB), Energy Filtered TEM (EFTEM) and STEM for semiconductor defects interception and high resolution observation. This method takes benefit of the specific imaging properties of respectively EFTEM and STEM techniques. A demonstration is presented for the observation of dislocations in a silicon integrated circuit.

Silicon defects such as dislocations are one of the major issues in Integrated Circuit fabrication. Due to their low distribution density these silicon defects are not easily observed using TEM cross section. in this paper we present a more appropriate technique using: FIB, EFTEM and STEM for such defects observation. First, in order to improve the probability of defects being present in the specimen, a very thick lamella is prepared using FIB. Then, using an energy filter for eliminating the inelastic electrons needed to allow thick specimen TEM imaging, direct defect localization and observation at medium resolution is carried out. After that, taking advantage of the beam broadening in the STEM, the defect position inside the specimen is more accurately evaluated. For that purpose two STEM observations are carried out from the two opposite specimen surfaces. The comparison of image contrast is used for further FIB specimen thinning. The process can be continued down to a thickness compatible with an acceptable spatial resolution TEM imaging.

Recently, several studies have been conducted to investigate the behavior of polymer based composites reinforced with clay particles, which can remarkably improve the properties of the polymers. Studies using transmission electron microscopy (TEM) are necessary to understand the role of clay minerals/particles in the reinforcing effect in the polymer based materials. TEM sample preparation of polymer/clay nanocomposites using conventional techniques has been difficult and tedious. Nevertheless, the focused ion beam (FIB) technique for preparing metal and ceramic samples provides another method for preparing polymer nanocomposite samples. This paper presents a new approach for preparing TEM specimens of the polymer nanocomposites using the FIB technique.

Two types of epoxy (Dow Chemical Company, DER 331) nanocomposite samples were investigated: one containing 7.5 wt.% organomontmorillonite clay (Southern Clay Products Inc., Cloisite 30B) and the other (carbon fiber reinforced plastics; CFRP) containing carbon fibers (Hexel Fibers, AS4) in addition to 5 wt. % clay. Details of preparing the epoxy based clay nanocomposites will be published elsewhere. Procedures for preparing TEM thin sections using FIB were based on techniques developed by Ramirez de Arellano et al.

In recent years, the availability of focused ion beam (FIB) milling systems has given a much-needed boost for transmission electron microscopy (TEM) as a technique for site-specific analysis. Much progress has been made in the area of site-specific cross-sectional and planar TEM sample preparation techniques. However, a continuing need exists to reduce the sample preparation time, in order to improve TEM cycle time for better support of process development, yield improvement and production in a high-volume industrial environment. Thus, a faster TEM sample preparation technique is always desirable to meet this demand. A new approach to TEM sample preparation is described in this paper.

Following the new approach developed in the present work, one can prepare on a single TEM grid at least two different cross-sectional samples of site-specific device structures or up to four different cross-sectional samples of blanket films. Two different samples, each containing an area of interest near the center, are cleaved or cut to a width of about 1.25 mm; these samples may be from two separate locations of a wafer, or from two different wafers where TEM analyses are required.