Cross-sectioning of microelectronic devices for the purpose of construction or failure analysis by SEM and/or TEM has always been considered a major challenge. The ever increasing complexity and shrinking dimensions of these devices have pushed the art and science of the related specimen preparation beyond their conventional limits. The need for SEM failure analysis of sub-micron elements of a failed device requires the capability of cross-sectioning the sample with a high spatial-resolution within a specific transverse piane. An image of the device structure obtained at sufficiently high magnification from the above specimen generally reveals the defect(s) responsible for the failure. If the imaging resolution and contrast offered by an SEM prove to be inadequate for the above purpose, device structure will be inspected via TEM. Analysis of such device by TEM imposes the additional requirement of back-thinning the above specimen to electron transparency at the site of failure.

I bought my last useful pocket calculator in 1975 and I still use it regularly. Every time I pick it up I know how to use it, since all the functions I need are printed on its buttons, and I expect to be using it when I retire, if I can still get the batteries. My son bought a “more sophisticated” calculator for his A-levels in 1988 and I inherited it shortly thereafter, it lies in my desk drawer but I cannot use it because it offers so much more than I need and there is too much printed on and around each button. I would need to read the manual every time I wanted to use it. On the desktop close by sits my telephone: It has 46 buttons and a 17-page manual and offers an enticing array of facilities. Unfortunately I only need each of these “facilities” about once a month and have never been able to memorize the necessary procedures. As a result all I can do is answer it when it rings and dial out.

The basic trick is to produce a very smooth, featureless background, preferably using low Z (atomic number) or low density materials. The following three methods exploit in 1: round glass coverslips, in 2: double stick tape and/or colloidal graphite paint for backgrounds, and in 3: a combination low Z plus high Z conductive coating strategy is described which when used in combination with 2, also produces the desired background effect.

1. I've done the following for pollen grains, rust spores, and soil particles (dried down onto glass coverslip support surface from water or ethanol, they just stick naturally), should work with larger samples, eg., insects, seeds, provided that any paint you use to mount the sample to the glass coverslip does not spread out beyond the edges of the sample so you don't see it in the background.

How many of the analytical chemists reading this will identify with the following scenario? A customer gives you a sample with a contaminant and asks you to identify the material. Your customer provides a very logical dissertation on what the material is likely to be. With that bias firmly entrenched in your mind, you proceed with the analysis, fully expecting to find what your customer said you should. However, during the course of your analysis, you discover that the contaminant is something completely different than expected. Now you are presented with the dilemma of facing that customer to explain the “unexpected” result. You are immediately put on the defensive by being accused of not having properly calibrated instruments or you have obviously contaminated the sample with something else during sample preparation, etc. These situations occur in laboratories all over the world.

In this day of resistance toward big science projects it may be futile to worry about how to produce the largest possible microscope. But since it doesn't cost anything to day dream, and times may change, it is fun to consider superlative enterprises.

One must grant that Ultra High Voltage Electron Microscopes are much larger than we wish they were, and one wonders if there is a contest afoot to see which AEM can have the largest foot print, but a new possibility has arisen which, seriously, could dwarf them all - yet have some possible use.

I am referring to the discovery of an example of a gravitation lens for ordinary light. Now the distinguishing characteristic of a microscope from a telescope is that the object eyepiece and the object near the focal length of the lens.

To adequately microscopically characterize opaque particles, and some finely divided, high refractive index, and transparent particles, one must use top light. This can be done with a built-in or accessory vertical illuminator. It can also be done without a vertical illuminator using any PLM with any separate microscope illuminator focusable to a small bright spot. Aimed downward onto the slide preparation at a steep angle, but missing the objective, and with the transillumination subdued or turned off, the color and surface texture of opaque particles can be readily discerned. The objective must have a long working distance, usually, therefore, a 10X or lower magnification.

Pseudo opaque particles (submicrometer particles of high index) are reaify transparent but hey may be colorless or any color. Top light brings out their true color - black, if opaque, but they may be red (Fe2O3), green (CR2O3), yellow (lead-tin yellow) or white (TiO2).

In microscopy, there is an increasing need for images to be recorded electronically and stored digitally on disk or tape. This image data can be shared by mailing these magnetic media or by electronic transmission along telephone lines (e.g. modem transfer) or special networks, such as Bitnet or Internet. In each case, the format in which the image is stored or transmitted must be known to the recipient in order to correctly recover all the information. Because there are many image formats to choose from, it would undoubtedly save misunderstanding and frustration if a group of individuals with similar interests and needs could agree upon a common format. The Microscopy Society of America Standards Committee has surveyed several formats which could be of particular interest to microscopist, with a view to making a recommendation to our community.

Force modulation Imaging is a scanning probe microscopy (SPM) technique that identifies and maps differences in surface stiffness or elasticity. It is one of several new techniques developed as extensions to the basic SPM topographical mapping capabilities. These techniques use a variety of surface properties to better differentiate among materials where topographical differences are small or immeasurable.

Force Modulation Imaging can be used in a wide range of applications including identifying transitions between different components in composites, rubber and polymer blends, evaluating polymer homogeneity, imaging organic materials on hard substrates, detecting residual photoresist on integrated circuits, and identifying contaminants in a variety of materials.

We have acquired and made available for loan a durable, easy-to-use, though expensive video-probe microscope. This hand-held, automatically focussing instrument can be used by a 5 year-old and provides instant, excellent, in-focus images of 50X to 200X on a video screen visible simultaneously to all students in the class.

The probe consists of a miniature video camera with interchangeable magnifying “objective” lenses which are surrounded with built-in, cool, fiber-optic illumination. Each lens is capped with a “contact tip” which corresponds to the focal length of the lens and which, when touching the sample, provides automatic focus of the image on the monitor. The images can be videotaped in the normal fashion.

Scanning acoustical microscopy has found a very comfortable niche in the area of non-destructive evaluation, testing and imaging. But the field need not be limited by such a narrow applications area.

In this article, a general review of current and possible applications will be conducted including archaeological conservation and evaluation. Part III of this series will deal exclusively with biomedical applications.

Since acoustical waves can penetrate a specimen, optically opaque materials can be visualized and more fully examined. Depending on the resolution required, a compromise needs to be achieved before a specimen can be imaged. Recall from Part I of this series, the higher the frequency, the better the resolution, but the depth of penetration is less. In many applications, it is not always necessary to achieve a high degree of resolution, it is more interesting to locate and identify internal structures. Acoustical microscopy is meant to be a complementary form of observation not necessarily a standalone modality.

Questions about samples consisting entirely of a collection of microparticles come from people involved in a wide variety of industries dealing with powders, from Pharmaceuticals to industrial minerals, powdered coatings to industrial hygiene concerns. The questions often asked are morphological. How big? How long? How wide?, and often pose a special problem for the microscopist. The time and tedium associated with answering these questions for a significant subset of the sample particles without an automated system causes the cost to skyrocket and sends the requester off to the light scatterers who at least give cheap answers, never mind that nobody knows what they really mean (What is the average size of a particle with an aspect ratio of 5? And did you calibrate your scattering system for my particles in my dispersant or are you still using latex spheres in water?). A common additional question is “How many are quartz, or titania, or organic, or….?” The inherent advantages of microscopy—the ability to determine detailed morphology in two dimensions (and maybe three), and to discriminate different particle types in a mixture—were usually overwhelmed by the cost and time involved.