X-ray microscopy using soft X-rays progressed successfully during past years. This paper discusses the atomic cross sections, the photoelectric absorption and the radiation damage for soft X-rays. Resulsts of contact microradiography are summarized. X-ray optics, which can be used for microscopy are zone plates, grazing incidence mirrors and normal incidence multi-layer mirrors, yet this has only been shown in practice with high resolution for zone plates. Details of the "Gottingen X-ray microscope" are given and a photographic image, showing 50 nm resolution, is shown. The future work of several groups is concentrated on the development of scanning X-ray microscopes.

The microfocal X-ray units have an extremely small X-ray source (5-15 pm diameter) acheived by focussing an electron beam onto the side of a solid target. High resolution magnification radiographs are obtained by placing the object close to the source and the recording surface at some distance away. The advantages of this type of X-ray are described as well as its applications in industry, bio-medical research and medicine. The high resolution and magnification of the radiographs enable precise measurements to be carried out.

The resolution of hydrated biological specimens by soft x-ray microscopy is considered. This is set by damage to the specimen caused by secondary electrons and free radicals. Using synchrotron radiation the limit would be about 10 nm. By using short lived (≈ 1 ns) sources as produced by a laser generated plasma, the Rayleigh limit of 2.3 nm should be possible.

Papers presented to this opening session of the conference have concentrated on the ap-plication of x-ray focusing methods in the soft x-ray region (10-50 Å). It is well known (see e.g. Duke) that this region is the one which must be exploited for the direct imaging of biological materials. It is also well known that great difficulties present themselves. These are primarily:-

A number of techniques are now available for the characterization of solid surfaces. The scanning electron microscope has firmly established its role in industry and elsewhere for routing high resolution studies of surface structure and topography and the addition of energy dispersive x-ray (EDX) analysis provides the technique with a powerful and comple-mentary method of elemental analysis. More recently, techniques such as the scanning auger microprobe (SAM), x-ray photoelectron spectroscopy (XPS or ESCA), and secondary ion mass spectrometry (SIMS) have become available which combine spatial resolution (of varying utility) with an ability to determine the composition of the outermost atomic layers (with varying precision and sensitivity). The remarkable depth resolution of these methods may also be exploited when used with surface sectioning techniques (such as sputter-etching) to provide composition-depth profiles. This lecture is aimed at introducing the principles and analytical procedures of these techniques and at illustrating their areas of application with examples of coullnercial importance in materials characterization, failure analysis, quality assurance and production problem solving.

The paper lists the principle sources of information in electron microscopy which become available due to the electron specimen interaction. It further describes the main electron optical and detector components and indicates how special operation modes of a transmission electron microscope based analytical system are obtained. Finally some of the possible applications are demonstrated on stainless steel and palladium catalyst specimens.

An automated method for quantitative determination of specimen topography is described in which a computer-controlled range finding technique is employed to measure the distance between the objective lens of a scanning electron microscope (SEM) and a set of distinct features on the specimen surface. Computations based on the spatial derivative of the image intensity allow the objective lens setting corresponding to the optimum focus for each feature to be determined, and this can be related to the feature height. Experimental results and theoretical analysis indicate that the sensitivity for discrimination of height differences is of the order of 1μm.

The principal advantages of the high voltage electron microscope, higher resolution, penetrating power, decreased radiation damage and the special effects of critical voltage and displacement damage are outlined. Some application of increased penetration and radiation damage to studies in materials science are then discussed in more detail.

The scanning electron microscope equipped with an x-ray spectrometer is a versatile instrument which has many uses in the investigation of crime and preparation of scientific evidence for the courts. Major applications include microscopy and analysis of very small fragments of paint, glass and other materials which may link an individual with a scene of crime, identification of firearms residues and examination of questioned documents. Although simultaneous observation and chemical analysis of the sample is the most important feature of the instrument, other modes of operation such as cathodoluminescence spectrometry, backscattered electron imaging and direct x-ray excitation are also exploited. Marks on two bullets or cartridge cases can be compared directly by sequential scanning with a single beam or electronic linkage of two instruments. Particles of primer residue deposited on the skin and clothing when a gun is fired can be collected on adhesive tape and identified by their morphology and elemental composition. It is also possible to differentiate between the primer residues of different types of ammunition. Bullets may be identified from the small fragments left behind as they pass through the body tissues. In the examination of questioned documents the scanning electron microscope is used to establish the order in which two intersecting ink lines were written and to detect traces of chemical markers added to the security inks on official documents.

Scanning acoustic microscopy, where the object to be imaged is scanned across the waist of a tightly focussed acoustic beam, has advances to the point where the resolution in water is comparable to that of a high quality optical microscope. The resolving power of the acoustic microscope can be further improved by resorting to a fluid which has a lower sound velocity than water. The two practical possibilities are cryogenic liquids, and higher pressure gases. Progress on both these fronts will be discussed. Improving the resolving power is only one aspect of our research effort: it is equally important to obtain quantitative information from the recorded images. We are working; on several schemes whereby it is possible to record the spatial frequency transmittance or reflectance of the object at the point being investigated and hence deduce the sound velocity and density on a microscopic scale. In order to make accurate predictions on the elastic parameters in certain experiments - such as the observation of stress near a crack tip - it is necessary to measure the phase of the acoustic beam with great accuracy. For this purpose, we have developed a differential interference contrast acoustic microscope which is the acoustic analogue of the optical nomarsky system. Finally, the great success of acoustic microscopy has led to the invention of many new forms of microscopy. Two such forms will be described - photodisplacement and photothermal microscopy - which are based on the microscopic measurement of some thermometric property. The use of such techniques to image current flow in integrated circuits and record optical absorption spectra of biological samples with a lateral resolution of a few microns will be described.

The Quate scanning acoustic microscope has now become established in university research groups, and interest is being shown from industry. The author has constructed a 1 GHz reflection instrument with lateral resolution better than 2 μm, and has been evaluating a number of possible applications. Some of these are discussed in detail and will include: (i) The examination of integrated circuit chips processed in MOS technologies, using the subsurface capability of the instrument. (ii) Metallurgical studies (iii) Thin-film studies, including organic thin films Emphasis will be placed on the merits of acoustic microscopy as opposed to other methods, and further developments of the technique likely to be of use will be discussed.

The principles and basic imaging theory of electron acoustic microscopy are outlined and illustrated with images of semiconductor devices. Image contrast arises from local variations in stopping power and thermal properties of the specimen but variations in elastic properties are also important. In elastically anisotropic materials the contrast depends on crystallographic grain orientation. Examples of such grain contrast are discussed as well as of grain boundary contrast which is interesting but less well understood.

Acoustic microscopy using liquid ⁴He offers the possibility of considerably higher resolution than microscopes at room temperature which use water as the coupling medium. At the same frequency the wavelength of sound in liquid helium is a sixth of that in water and because there is no attenuation in liquid ⁴He there is the possibility of using much higher frequencies than is presently used (3 GHz) with water. The properties of liquid ⁴He rele-vant to this application are reviewed together with the equipment necessary to work at 0.1K. The information likely to be obtained from helium microscopy is considered and compared to room temperature acoustic microscopy. Although helium acoustic microscopy is still in its infancy recent results indicate that it is likely to be a valuable new tool.

Images are presented which illustrate applications of the scanning acoustic microscope to problems in studies of materials. In transmission the structure of a diffusion bond is revealed; in reflection images of grains, cracks and oxides are shown. A theoretical outline is given indicating how the microscope may be used as a quantitative elastic microprobe.

The problems of making accurate measurements of critical dimensions of features on integrated photomasks and silicon wafers are discussed and the currently employed optical measurement techniques described. Sources of systematic uncertainty in such measurements are considered. Measurement equipment developed at NPL and the NPL Photomask Linewidth Standard are described, and approaches to profile measurement of features on silicon wafers are discussed.

The scanning optical microscope (SOM) provides new information concerning a wide range of specimens. It is particularly advantageous for study of materials and devices, including semiconductors. The image is built up on a TV-type display by mechanically scanning the object across a focussed laser spot.

Crystalline semiconductor materials often contain structural defects which can influence adversely both the behaviour during processing and the ultimate performance of devices fabricated from them. Traditionally structural perfections have been assessed by the optical microscopy of chemically etched surfaces and augmented by X-ray and electron microscopic techniques when detailed analyses are required. Polarised infrared microscopy (PIM) is emerging as a non-destructive technique for the real time imaging of defects ranging in size from locally strained regions several millimetres across, down to single dislocations. This paper discusses the present state of PIM development, with examples taken principally from the field of opto-electronic materials. The performance of a polarizing microscope operating at near-infrared wavelengths is described for three distinctive imaging modes. In these modes, defects which absorb the illumination or cause stress birefringence or non-radiative carrier recombination in photoluminscent materials respectively are revealed with an optimum resolution of about 1 μm.

The application of holography to microscopy is outlined with special reference to the identification of fossil ostracods using a stereomicroscope. The effect of laser speckle on the image quality is demonstrated and a speckle reduction technique based on the incoherent superposition of many differently-speckled reconstruct-ions of the same object is discussed. A holographic attachment for a standard stereomicroscope is described in which this speckle reduction technique is implemented by means of a holographic lens array, and results are shown.

Constituents in metal alloys and rocks may be seen as different colours using interference film microscopy. The thin films which produce the interfeference colours may be deposited either by vacuum evaporation or reactive sputtering . Tne technique is used in a wide range of investigatons which require identification of phases quickly and easily, e.g. in nickel-base superalloys and hard metals. The theory, techniques for optimising the performance and a method of quantifying the results by microspectrophotometry will be discussed and a case study presented.

Recent developments in technology have led to the wide availability of image analysis systems suitable for particle size analysis, and one such system is described. Image analysis offers a significant advantage over manual microscopy as it allows large numbers of particles to be measured consistently and accurately. The image presented to the image analyser must be carefully prepared in order to reduce measurement errors to a minimum. Good sample preparation techniques are much more important here than for manual microscopy, and the greatest care must be taken when setting up the microscope/tv camera imaging system. Many more measurements can be made on each particle than would be possible manually, and several methods of calculating the particle size are described. The use of automated focus, slide transport and slide changing mechanisms under the control of the image analyser can eliminate the need for manual intervention in the system, allowing it to be run overnight.

A new three dimensional measuring instrument is described which uses a stereoscopic microscope. Objects of up to 100 x 100 x 60mm can be measured without physical contact, with repeatability spreads of 20μm Proposed improvements are described which could reduce the spreads to 10μm.