The thinning technique is based on a simple geometrical model, describing the changes in the surface topography during ion beam etching. A high ion beam density makes jt possible that a thinning with an incidence angle of 0.5–7° ( measured from the sample surface) can take place within a reasonable time. Our method is applicable to a wide range of materials and to XTEM preparation.

In the semiconductor industry, shrinking geometries and increasing process complexity have greatly increased the demand for TEM analysis of specific submicron regions. Until recently, samples of this nature have been difficult if not impossible to prepare. We have combined cross-sectional TEM sample preparation (XTEM) and the precise material sputtering of focussed ion beam milling (FIB) to thin samples to electron transparency. We call this sample preparation technique FIBXTEM.

Three advantages of this technique are: 1) The area of interest can be analyzed in the scanning electron microscope before final thinning; 2) Any specific defect area becomes a candidate for TEM analysis, including failed sub-micron structures; and 3) Samples are generally artifact-free and of uniform thickness.

Key elements of the FIBXTEM technique include precision planar polishing, unique holders for mounting and transferring samples between systems, and the FIB-induced deposition of a sacrificial protective layer over the area of interest during ion thinning.

This technique extends the use of TEM analysis into new areas of semiconductor process development and failure analysis. Recent applications for materials problem solving and failure analysis are discussed.

The article describes the design, construction and performance of a new bench top instrument for high speed ion beam thinning and polishing of materials. In this system, the combination of very low angle ion milling and powerful ion guns has led to the rapid production of high quality TEM specimens. The main subassemblies are (1) a work chamber (2) gas control system (3) vacuum system and (4) electrical system. The work chamber consists of a pair of newly designed Penning type ion guns and Faraday cups to measure ion currents. The Whisperlok™ mechanism provides specimen rotation, pneumatically driven airlock for very fast specimen exchange and transmission/reflection illumination for specimen viewing. The ion guns are mounted to deliver a nominal, 4° milling angle on the specimen surface with precision alignment of ±2° about horizontal and vertical axes. The actual thinning is undertaken from one side using a single, post-type specimen holder which minimizes the specimen heating and contamination. The ion beam current of each gun can be individually optimized by varying the flow rate of the ionizing gas. The main chamber is evacuated by diaphragm and molecular drag pumps to produce a clean, dry vacuum in the 10−6 Torr range. The discharge and accelerating voltages required for the operation of each gun are provided by a dual high voltage power supply capable of delivering ion energies in the range; 1 keV to 6keV. TEM micrographs of typical ion polished specimens of semiconductors, metals, ceramics and composites are included to illustrate the performance of the instrument.

The construction and performance of an updated gas source precision ion milling system are described. The system is based on an existing focused ion beam machine which is able to image and mill selected areas of specimens that are too thick for TEM studies. The specimen image is formed using either secondary electrons or secondary ions, captured by a dual detector. The work chamber consists of three major components: the ion gun, the ion column and the specimen chamber. The ion gun is an electron impact ionization type with an optimized source size and allows the use of variety of gases. The updated system employs an objective lens with shorter focal length to enhance the resolution. The specimen chamber with an improved specimen eucentric stage, accepts side entry TEM specimen holders. This enables the specimen to move between the TEM and the instrument for further precision thinning as required without removal of the specimen from the holder and consequent risk of damage. The upgraded system resolves features <1μm in thickness. Its point milling rate for Ni is 1.4μm/min. The ability of the instrument for imaging and localized milling is demonstrated by a number of TEM images of semiconductors, metals, ceramics and composites.

Many of today's advanced materials are prepared using a combination of ultrasonic disk cutting, dimpling, and ion milling. In order to optimize the analytical results from a single specimen, several improvements have been made in instrumentation for ultrasonic disk cutting. Also, a system has been developed for detecting either at or near-electron transparency in TEM specimens. Both of these aspects are described. Examples are provided for silicon, metal/ceramic composites and blanket substrate layers for electronic devices.

One of the latest advancements in technique for preparing materials for TEM examination was first made commercially available by VCR Group in 1982. The instrument, known as the DIMPLER®, mechanically thins materials by “dimpling”, a technique which has become widely accepted by material scientists. Since its inception other manufacturers have also produced dimpler-like instruments.

A small-angle cleavage technique has been developed for transmission electron microscopy (TEM) of semiconductors and related materials. In this technique, samples are prepared by back-thinning the material to a prescribed thickness, back-scribing the material at a specific angle to a standard cleavage plane, and cleaving along these scribe lines. A second cleave is made along the standard cleavage plane to intersect the first cleave, forming a thin wedge. This wedge is mounted on a grid, providing an electron transparent tip free of ion milling artifacts.

Cross sections of material specimens for TEM analysis must be produced in the shortest time possible, contain few, if any, artifacts and have a large area available for analysis. The analyst must also be able to prepare these cross sections from specified areas of complex, heterogeneous structures on a routine, reproducible basis to meet the growing needs of the semiconductor industry for TEM analysis. The specimen preparation spatial resolution required for preparing precision cross sections is substantially less than one micron. Cross sections meeting these requirements can be prepared by mounting a specimen to the Tripod Polisher and mechanically polishing on one side of the specimen, using a sequence of progressively finer grit diamond lapping films, until the area of interest is reached. This polished surface is then very briefly polished on a cloth wheel with colloidal silica to attain the final polish on that side. The specimen is then flipped over on the Tripod Polisher and polished from the other side, using same sequence of diamond lapping films to reach the predefined area of interest. The Tripod Polisher is set at a slight angle, to produce a tapered, wedge-shaped specimen, which has the area of interest at the thinnest edge of the taper. The specimen is polished with the diamond lapping films and the colloidal silica until it is 1000 Angstroms or less in thickness. The specimen is removed from the polisher and mounted on a 2 × 1mm slotted grid with M-Bond 610 epoxy. After the epoxy is cured the specimen can be taken directly to the microscope for analysis. The need for ion milling has been eliminated or reduced to a few minutes in most of our work because of the thinness of the final specimen. The total specimen preparation time is between 2.5 and 4 hours, depending on the specimen and the size of the specified area. The area available for analysis ranges from 0.5mm up to the full size of the mounting grid opening. The wedge shape of the specimen provides the mechanical stability needed for a long thin specimen.

It is now a requirement in the semiconductor industry to prepare TEM specimens of pre-specified regions with a specimen preparation resolution exceeding 100nm. In other words, given the coordinates x, y, z of the location desired for TEM analysis, the TEM specimen preparation procedure must yield a thin TEM specimen containing the point x, y, z plus or minus 100nm. Preparation of failure analysis specimens in other fields of endeavor, such as: metallurgical, ceramic, composite material laboratories etc., have specimen preparation spatial resolution requirements below one micron in some cases with the likelihood that greater precision will be required in the future.

A method for the preparation of planview transmission electron microscope (TEM) specimens of expitaxial Yba2Cu3O7−x (YBCO) thin films deposited on BaF2 by a dc modified planar magnetron sputtering technique is reported. The films are granular with their grains size ranging from a few hundred to a few thousand nanometers. The epitactic nature of the film growth is shown by analyses of moiré fringe patterns and by selected area diffraction methods. It is demonstrated that the YBCO thin film obtained is highly c-axis oriented, with misorientation corresponding to rotations of 9.2° and 90° about the c-axis. Additionally, the film's a or b axes form a 45° angle with that of the substrate.

A computer-controlled, specimen rotation attachment was developed and installed on a commercial ion-milling system for TEM specimen preparation. This rotation method produced relatively large thin areas on a variety of thin film transverse specimens with a difference in the ion-milling rates between the film and the substrate. The results were generally comparable to those obtained by a newly developed low-angle ion-thinning procedure and the overall processing time was considerably shortened.

A preparation technique for the production of cross-sectional transmission electron microscope (TEM) samples from the interdiffusion regions of Fe-Zn binary couples is described. To alleviate the problem of unequal ion milling rates between the Fe and Zn, a 0.75mm thick Fe sheet has been double plated with a thick electrodeposited Zn coating to achieve a total couple thickness of ˜3mm. After slicing the couple in cross-section, the Fe region of the sample is dimpled to perforation near the Fe-Zn interface. Final thinning for TEM analysis is obtained by ion milling using a liquid nitrogen cold stage and sector speed control. The ion milling procedure is stopped when the perforated hole in the Fe-side of the couple extends through the faster eroding Zn-side of the interface. This technique, in modified form, is expected to be suitable for commercial steels coated with Zn-based alloys.

Improvements in specimen preparation for TEM analysis are being constantly sought, particularly in the study of microelectronics' materials and in failure analysis of devices. We describe here a compact commercial system capable of thinning (milling) selected regions of a specimen by means of a scanned focused ion beam of sub-micron spatial resolution.

The increased usage of indentation testing for the determination of the toughness of brittle materials has raised many questions about the nature and extent of plastic deformation in these materials. Of particular interest is the behavior of single crystal silicon in indentation (hardness) testing. Recent studies point to some interesting properties of silicon under indentation loading and unloading. The least understood of these properties is the apparent phase change and subsequent cracking that the crystalline silicon experiences upon indentation. The pressure induced phase transformation is thought to proceed by crystalline Si changing to metallic and then changing to amorphous. Accompanying this phase transformation is usually a characteristic cracking pattern.

It is the goal of a larger study to characterize the deformation process during indentation. This can be best achieved by producing an electron transparent cross section of a microindentation which is suitable for structural characterization using a Transmission Electron Microscope (TEM). The various conventional and unconventional methods we have attempted to employ to produce suitable samples, the problems we have encountered, preliminary results, and proposed modifications are discussed.

TEM specimens of PREPed Ti -48 at.% Al powders can be prepared reproducibly in a straight-forward manner. There are two kinds of powders with respect to surface and crosssectional morphologies. One is with an Widmanstitten-like structure and or a surface relief of martensitic phase and the other is with a dendritic structure. The primary phase during solidification and relative cooling rate in both the powders are discussed by comparing the macroscopic and microscopic features.

The preparation of cross-sectional specimens for materials such as tungsten carbide containing ceramic coatings presents some unique problems. Pieces joined by the use of epoxies often separate at this interface during subsequent preparation steps as a result of the vibration and physical strain placed on the sample during the initial mechanical grinding and subsequent thinning process. These problems have been overcome through the use of a preparation process which essentially encapsulates the sample within the confines of an epoxy filled quartz tube. This preparation process has allowed for the cross-sectional analysis of Al2O3/TiC coatings on WC substrates and has revealed two distinct grain morphologies within the TiC coating.

The sample preparation procedures which enable us to observe large areas over a few tens of microns in one-dimension of semiconducting heteroepitaxial materials are described. The main principle involves the careful grinding and polishing of samples. In these procedures, another side thinning of the specimen after finishing initial side polishing is carried out using a sample platform by hand throughout all of the following steps. It is shown that for some typical examples of heteroepitaxial films general information concerning the film growth modes and structures, as well as the defect morphologies and natures introduced during growth can be effectively obtained by using the present technique.

An alternative VLSI TEM specimen preparation technique has been developed to produce 100μm diameter electron transparent thin area by using a conventional dimpler with a texmet padded ‘flatting tool’ for dimpling and a microcloth padded ‘flatting tool’ for polishing, followed by low angle ion milling. The advantages of this technique are a large sampling area and shorter milling times than conventional specimen preparation methods. In the following, we report the details of the modified dimpling technique. The improvements in available electron transparency, and a decrease in ion milling time are demonstrated with the preparation of planar and cross section VLSI device samples.

A novel and efficient technique for the generation of nanoscale metal particles by the electron beam decomposition of metal hydrides and azides is presented. Nanoscale metal particles down to ∼ 25 Å in diameter can be generated from metal hydrides e.g. copper from CuH and from metal azides e.g. silver from AgN3. The technique has been successfully applied to Be, Mg, Al, Cu, Pd, Ti, ‘Mn, Ni, Ag, Sn, Fe, Bi, Cd, Sb, Ln and Tl.

This study presents novel methods for chemically preparing back-side and double-side etched, plan-view TEM samples without use of jet thinning instrumentation in order to examine both surfaces and interfaces. Examples are drawn from the semiconductor industry, but this technique can be generalized for use in most materials systems. The methodology for single-sided etching consists of flat lapping and mechanical dimpling followed by material selective chemical etching to electron transparency. Interface defect analysis of heterostructures is achieved via double-sided etching to electron transparency using the proper selective chemical etchants. These techniques are presented not as replacements for conventional cross-sectional preparatory techniques, but instead, as a means for rapid sample preparation for situations where a large number of samples must be analyzed quickly, or in cases where the necessary equipment is lacking for crosssection preparation.