Analytical techniques electron beam

The physical techniques used in IC analysis all employ some type of primary analytical beam to irradiate a substrate and interact with the substrate s physical or chemical properties, producing a secondary effect that is measured and interpreted. The three most commonly used analytical beams are electron, ion, and photon x-ray beams. Each combination of primary irradiation and secondary effect defines a specific analytical technique. The IC substrate properties that are most frequendy analyzed include size, elemental and compositional identification, topology, morphology, lateral and depth resolution of surface features or implantation profiles, and film thickness and conformance. A summary of commonly used analytical techniques for VLSI technology can be found in Table 3. 

The SNMS instrumentation that has been most extensively applied and evaluated has been of the electron-gas type, combining ion bombardment by a separate ion beam and by direct plasma-ion bombardment, coupled with postionization by a low-pressure RF plasma. The direct bombardment electron-gas SNMS (or SNMSd) adds a distinctly different capability to the arsenal of thin-film analytical techniques, providing not only matrbe-independent quantitation, but also the excellent depth resolution available from low-energy sputterii. It is from the application of SNMSd that most of the illustrations below are selected. Little is lost in this restriction, since applications of SNMS using the separate bombardment option have been very limited to date. 

Nearly all these techniques involve interrogation of the surface with a particle probe. The function of the probe is to excite surface atoms into states giving rise to emission of one or more of a variety of secondary particles such as electrons, photons, positive and secondary ions, and neutrals. Because the primary particles used in the probing beam can also be electrons or photons, or ions or neutrals, many separate techniques are possible, each based on a different primary-secondary particle combination. Most of these possibilities have now been established, but in fact not all the resulting techniques are of general application, some because of the restricted or specialized nature of the information obtained and others because of difficult experimental requirements. In this publication, therefore, most space is devoted to those surface analytical techniques that are widely applied and readily available commercially, whereas much briefer descriptions are given of the many others the use of which is less common but which - in appropriate circumstances, particularly in basic research - can provide vital information. 

In 1951Castaing8 published results to show that an electron microscope could be converted into a useful x-ray emission spectrograph for point-to-point exploration on a micron scale. The conversion consisted mainly in adding a second electrostatic lens to obtain a narrower electron beam for the excitation of an x-ray spectrum, and adding an external spectrometer for analysis of the spectrum and measurement of analytical-line intensity. Outstanding features of the technique were the small size of sample (1 g cube, or thereabouts) and the absence of pronounced absorption and enhancement effects, which, of course, is characteristic of electron excitation (7.10). Castaing8 gives remarkable quantitative results for copper alloys the results in parentheses are the quotients... 

Electron energy loss spectroscopy An analytical technique used to characterize the chemistry, bonding, and electronic structure of thin samples of materials. It is normally performed in a transmission electron microscope. The inelastically scattered electron beams are spectroscopically analyzed to give the energy spectrum of electrons after the interaction. 

Three analytical techniques which differ in how the primary vacancies are created share the use of such X-rays to identify the elements present. In X-ray fluorescence, the solid sample is irradiated by an X-ray beam (called the primary beam), which interacts with the atoms in the solid to create inner shell vacancies, which then de-excite via the emission of secondary or fluorescent X-rays - hence the name of the technique. The second uses a beam of electrons to create the initial vacancies, giving rise to the family of techniques known collectively as electron microscopy. The third and most recently developed instrumentation uses (usually) a proton beam to cause the initial vacancies, and is known as particle- (or proton-) induced X-ray emission (PIXE). 

Convergent-Beam eleetron Diffraction and Microdiffraction) become available on analytical transmission electron microscopes. Most of the electron diffraction techniques use a stationary incident beam, but some specific methods like the precession method take advantage of a moving incident beam. 

All analytical techniques in the TEM are based on the inelastic scattering of the fast beam electrons by the electrons of the atoms in the material investigated. The primary event in each case is the transfer of energy and momentum from the fast electron to a sample atom, thereby exciting the... 

Because many environmental particles are poor electrical conductors, charging produced by the incident electron beam is a major analytical concern in EMP and SAM (11,14). Because EMP analysis is not very surface specific, the sample surface is normally coated with a thin film of a low Z conducting material such as C. The surface specificity of the Auger technique generally precludes the use of surface coatings, and electrical charging of the particles may be exceedingly difficult to overcome experimentally (11, 14). 

The amount and uniformity of the solid state reaction of halogen with TTF was probed by the electron microprobe technique. In this analytical method, low energy electron irradiation of a sample provides X-ray core level emissions, characteristic of the element and its relative concentration. Our initial analyses indicated a dramatic dependence of the halogen concentration with the energy of the electron beam. To probe this phenomenon further,... 

A striking feature of the ILs is their low vapor pressure. This, on the other hand, is a factor hampering their investigation by MS. For example, a technique like electron impact (El) MS, based on thermal evaporation of the sample prior to ionization of the vaporized analyte by collision with an electron beam, has only rarely been applied for the analysis of this class of compounds. In contrast, nonthermal ionization methods, like fast atom bombardment (FAB), secondary ion mass spectrometry (SIMS), atmospheric pressure chemical ionization (APCI), ESI, and MALDI suit better for this purpose. Measurement on the atomic level after burning the sample in a hot plasma (up to 8000°C), as realized in inductively coupled plasma (ICP) MS, has up to now only rarely been applied in the field of IE (characterization of gold particles dissolved in IE [1]). This method will potentially attract more interest in the future, especially, when the coupling of this method with chromatographic separations becomes a routine method. 

Analytical electron microscopy is the most sophisticated tool available for micro-structural analysis today. In this method, we can obtain both the high-resolution structure and elemental composition of a specimen. This is probably the best technique to obtain local elemental composition of small regions of heterogeneous solids. When a high-energy electron beam is incident on a specimen, we get elastically and inelastically... 

X-Ray Photoelectron Spectroscopy (XPS). This technique is also known as electron spectroscopy for chemical analysis (ESCA), and as this name implies, it is a surface analytical technique. At present it is probably the most versatile and generally applicable surface spectroscopic technique. It is called XPS because of the type of beam used to study the interfacial region, that is, X-rays. These X-rays consist of monochromatic radiation—radiation of a given energy—emitted by a metal target bombarded by an electron beam of several kiloelectron volts of kinetic energy... 

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