Diamond knife sectioning, or ultramicrotomy, is being used increasingly as an attractive alternative or complimentary means of producing quality TEM specimens. This paper represents a first attempt to provide a basic methodology for this technique for materials scientists, point out its drawbacks, provide a comprehensive listing of more than three decades of widely-scattered and ingeneous applications, and illustrate the diversity of these applications with clear examples. Suggestions will be made for further improvements in ultramicrotomy so that it can be applied in a more routine fashion to modern advanced materials or TEM applications involving demanding chemical microanalysis.

This paper summarizes methods used to create cross-sectional samples for transmission electron microscopy and introduces another variant of the technique all of which rely upon some combination of lithographic patterning and reactive ion etching. The basic idea pursued in using these techniques was to form, from a preselected location, samples that had a large transparent area without use of mechanical polishing or ion milling. Samples were successfully prepared in this manner, but room for improvement remains due to the limited range of diffraction conditions available for imaging or diffraction pattern formation.

Experience has shown that the difficulties encountered in jet polishing of TEM foils can be minimized by the selection of equipment and an electrolyte appropriate for each material. The use of a jet polishing instrument for more than one type of specimen preparation after minor modification will be presented. Some insights on the relationship and manipulation of the parameters involved in achieving well polished TEM foils having appropriate surface quality, thin area, and perforation size will be included. Methods used to develop new electrolytes for specific purposes and the results of their use on both conventional and superconducting materials will be shown. A technique to calibrate equipment for more reproducible specimen hole size, use of new electrolytes on various materials, the salvage of unsatisfactory foils, and thinning of undersized specimens will be reviewed.

Ion-milling-based sample preparation has the advantage that thin area can be obtained from almost any material. It has the disadvantage, however, that the amount of thin area can often be quite limited. This poses a problem when a large sampling area is needed from materials which must be thinned by ion milling. Cross-sectioned samples and grossly heterogeneous materials are two examples where this problem may be encountered. The group at IBM in East Fishkill have developed methods for mechanical grinding and polishing of TEM samples down to about I micron thickness. They use this as a starting point for final thinning by ion milling. This approach produces a large uniform thin area in a short time in the ion mill. We have built jigs that allow us to make these mechanically-thinned samples. We have also made flat-bottomed dimples using ultra-precision dimple grinders to achieve similar results. Both of these approaches are described. Examples are taken from cross-section samples of thin films on silicon, from steels with large carbides, and from rapidly solidified metal spheres embedded in electroplated copper.

Chemically assisted ion beam etching (CAIBE) is widely practiced in the semiconductor industry. In the electron microscopy field, the CAIBE technique offers a new method for preparing specimens that are difficult to make by conventional inert gas milling techniques, e.g. indium containing type III-V compound semiconductors. CAIBE employs a collimated, molecular beam of a reactive species, e.g. iodine in combination with a conventional inert gas fast atom beam for thinning TEM specimens. CAIBE should not be confused with reactive ion beam etching (RIBE) which takes a chemically active species (e.g. iodine) and converts it into a beam of fast ions directed at the sample. CAIBE has three major advantages over (RIBE): i) corrosion of the ion gun components does not occur, ii) much smaller quantities of reactive gas are required and hence pump maintenance and pollution problems are minimized, iii) a wider range of chemicals may be used. Superior results are obtained if CAIBE is done on only one side of the specimen at a time. This is achieved using a new type of specimen holder post which enables very low angle milling and minimizes specimen contamination by sputtering from the holder. This new technique is described and results from iodine CAIBE milling, iodine RIBE milling and argon ion milling are compared for InP, InSb and GaAs as well as metals like tungsten. Also, the beneficial effects of very low angle (∼1°) argon ion milling in preparing specimens of silicide containing Si based IC wafers is reported.

A long term aim of this study is to overcome the difficulties to use electron microscopes (TEM, SEM) for in situ experiments, which includes (1) a preparation of initially clean surfaces, (2) a use of specimen micro-chambers, (3) in situ heating, (4) devices to produce and analyse reactions and (5) video registration. An interesting step in this direction is the replacement of the usual thin films by specimens in form of tips similar to those used in field emission devices. A tip is first prepared by electrolytic etching. Then the tip is cleaned and shaped in vacuum. This opens the possibility to visualize and measure kinetic phenomena up to higher temperatures than so far (1500 K and more). Examples of results are: (1) Surface matter fluxes and surface self-diffusion can be measured, (2) solid/solid interfaces and their displacements (reactions) can be measured, (3) grain boundary displacements and grain rotations can be measured and (4) periodic electric discharges between electrodes of 0.1 gim on specimens are prepared, visualized and explained.

Samples of high Tc superconductors and metal powders have been prepared for Scanning and Transmission Electron Microscopy examination by a novel method. Dental amalgam, commonly used for filling cavities in teeth by dentists, has been used as a binding agent to hold the sample particulate together during sample preparation. The amalgam was pressed into a small rod 3 mmn in diameter and samples were prepared by cutting slices from the rod followed by mechanical grinding and ion milling to perforation. This technique is extremely easy and offers several advantages over other preparation methods. Experiments revealed difficulties due to preferential sputtering yield, but generally these could be overcome and good thermal and electrical properties of the amalgam partially offset the former inconveniences. It should be possible to use this technique for any number of materials, including ceramic materials and small non-spherical particulate.

Epitaxial PbTe and CdxPb1−xTe films have been grown on single crystal (111) BaF2 by low energy bias sputtering, and have been analyzed by transmission electron microscopy (TEM) and transmission electron diffraction (TED). Preparation of suitable cross-sectional TEM samples was made difficult by the tendency of the substrate to cleave apart during dimpling, and by the epoxy forming bridges across the sample during atom milling. Suitable preparation techniques were developed employing back-polishing the BaF2 substrates to <0.2 mm thickness, using a suitable epoxy, and shielding the argon atom beam during milling to prevent milling parallel to the surface. In cases where an epoxy bridge did form across the sample, the bridge was broken manually or by atom milling, depending upon the area of sample which was being investigated. These techniques are applicable to other materials which produce similar problems during TEM sample preparation.

For materials that are conducive to pre-thinning by mechanical techniques, a combination of dimpling and ion milling is commonly employed to produce TEM specimens. In order to minimize artifacts induced by ion milling and to provide an increased electron-beam transparent area, new instrumentation for mechanical thinning has been developed. Examples illustrating the utilization of this instrument in the preparation of cross-sectional interfaces from layered samples are discussed.

A technique was developed to prepare crystalline fibers of less than 1 mm diameter for transmission electron microscopy. Cross sections were made by casting a short piece of the fiber in an epoxy resin, sectioning the block, and laminating the slices against thin glass discs for stability before dimpling. Longitudinal sections were reinforced in a similar manner. TEM tungsten rings were sometimes used as an alternative method to add stability to the longitudinal sections. The technique was especially developed for Bi-Sr-Ca-Cu-O compounds but is also suitable for other materials.

Uniformly thin specimens of powders, suitable for electron microscopy, can be prepared by ultramicrotomy. There is a size limit to the particles that can be studied since larger particles tend to be dislodged from the available resins when microtomed. A method is described to strengthen the binding of the organic resin to the inorganic zeolite, allowing large particles to be sectioned. The particle size limit increased from 3 μm to greater than 20 gim in diameter for FeZSM-5 aggregates. This method can be applied to a variety of oxide powder samples, extending the utility of microtomy as a materials science tool.

For studies of particles suspended in air or water, material is commonly deposited onto membrane filters. Submicrometer particles collected in or on the surface of the filters can be prepared for analysis by TEM by extraction replica methods. To identify the problems and artifacts generated during the preparation process, evaluations were made of replicas prepared internally at NIST and prepared by laboratories involved in the analysis of air-collected asbestos. Problems or artifacts that could affect the counting and analysis of asbestos particles were identified and characterized. Results of evaluations of replicas prepared by eighteen laboratories in an interlaboratory study are summarized.

In this paper we present a rapid and highly precise plan view and cross-section specimen preparation technique for the localized thinning of semiconductor devices for TEM investigation. No special equipment except the commercially available one is required. Crosssection preparation takes about 6 hours, while plan view takes about 4 hours. Prespecified areas of 0.6 μm wide and 10 μm long can easily be thinned with transparency for CTEM and HREM. Using an iterative ion milling procedure allows to scan a complete device in HREM.

A procedure for batch processing of up to four specimens for cross-sectional transmission electron microscopy (X-TEM) has been developed. The technique is essentially an extension of the standard multi-slice composite full disc sample preparation method. However, disc cutting and dimple grinding steps have been eliminated. The trimming, gluing, stacking, and sectioning of the wafers from the original sample material to produce composite transverse sections are identical to those of the standard scheme. Grinding and polishing of the sections are carried out in a batch mode which, in turn, reduces the overall processing time per specimen. The prepared composite foils are mounted on metallic disc grids which provide structural support during ion thinning and microscopy.

The as-produced high hardness of rapidly solidified aluminium powder alloys make TEM specimen preparation difficult. Conventional methods, i.e. electrothinning or ion-beam thinning of electroplated foils or compacts, although adequate for some powders, are not suitable for many other new and novel alloy powders. In this paper we discuss ultramicrotomy of such powders and the prospects and limitations of the method.

The procedures described in this paper allow both SEM and TEM analysis to be performed on the same, device specific, semiconductor cross section. In order to accomplish this, a number of tools and fixtures have been constructed that allow the user to polish into the sample to a predetermined plane-of-polish, bisecting the device or feature of interest for SEM analysis. After SEM examination, the specimen is prepared for TEM analysis by first affixing a grid to the just-examined surface, inverting the specimen and parallel-polishing the backside of the specimen until the specimen's total thickness is in the 0.5 to 1.0μm range using the described tools. A subsequent one to ten minute ion milling step cleans the specimen. A very considerable positive side-effectof this method is the nearelimination of artifacts arisingfrom the use of strong chemicals and lengthy ion milling. The method has been extended to the preparation of plan-view device samples and non-semiconductor specimens.

A new technique using a focused ion beam has been developed for the fabrication of transmission electron microscopy specimens in pre-selected regions. The method has been proven in the fabrication of both cross-sectional and planar specimens, with no induced artefacts. The lateral accuracy achievable in the selection of an area for cross-sectional analysis is better than one micrometre. The technique has been applied to a number of silicon and III-V based integrated circuits, and is expected to be suitable for many other materials and structures.

This paper presents the specimen preparation approaches developed to image rubber(butadiene) - modified epoxy polymeric materials used in the microelectronics industry by TEM. The methodology is complicated by the fact that silica and calcium carbonate (>75 wt%) are used as filler materials while the rubber is used as a toughening agent in the samples investigated.

Single crystal MgO is a common substrate for the deposition of oxide thin films. The conventional cross sectional transmission electron microscopy sample preparation procedure suffers the drawbacks of: 1)- extensive ion milling time; 2) a higher milling rate for the thin films than for the substrate; 3) introduction of artifacts and contamination during ion milling; and 4) generation of excess defects into the substrate during mechanical thinning. An additional chemical thinning step using hot orthophosphoric acid can reduce or eliminate these adverse effects.

This technique can be applied generally to thin film samples deposited on substrates with a low ion milling rate. Furthermore, substrates which are sensitive to mechanical stress and ion beam damage are also suitable for this technique, provided an appropriate chemical polishing solution and compatible epoxy can be found. The unique features of this technique are briefly presented.

A modified “two-in-one” cross-sectional TEM sample preparation technique is described. By coating a thin layer of “marker” to distinguish one sample from the other, two samples could be simultaneously prepared in one TEM cross-sectional specimen. Therefore, the specimen preparation time is reduced by nearly one half. The coating can be done in an existing ion-mill. Criteria for choosing a suitable marker as well as tips on getting good quality specimens are described. An example of applying this technique to a processing-microstructure study of an ultra-shallow junction formation in silicon is demonstrated.