Insulators analysis

Sample requirements Solid conducting material, vacuum compatible flat wafer up to 5-mm diameter insulator analysis possible... 

In insulator analysis an electron gun is also necessary to compensate for the positive ion current at the sample surface. Two types of operation are typical. 

Technique Primary probe Elemental range Type of information Depth of information Lateral resolution Sensitivity (at. %) Ease of quantification Insulator analysis Destructive UHV environment... 

The closely allied topics of secondary neutral mass spectrometry (SNMS), fast atom bombardment (FAB), and laser ablation SIMS are important, but are beyond the scope of this chapter. SNMS is a technique in which neutral atoms or molecules, sputtered by an ion beam, are ionized in an effort to improve sensitivity and to decouple ion formation from matrix chemical properties, making quantification easier. This ionization is commonly effected by electron beams or lasers. FAB uses a neutral atom beam to create ions on the surface. It is often useful for insulator analysis. Laser ablation creates ions in either resonant or nonresonant modes and can be quite sensitive and complex. 

SIMS (Quadrupole) Quadrupole Sims Dopant and impurity depth profiling, surface and microanalysis, insulator analysis Secondary ions 10 -10 atoms <50 A <5 pm (imaging) >30 pm (depth profiling)... 

Some specific problems undertaken include location of heavy metals in soil specimens due to application of sewage sludge, trace element profiling in electrical insulators, analysis of air particulate collected at urban locations, multilayer thin film analysis of solar cells. 

Dielectric constants of metals, semiconductors and insulators can be detennined from ellipsometry measurements [38, 39]. Since the dielectric constant can vary depending on the way in which a fihn is grown, the measurement of accurate film thicknesses relies on having accurate values of the dielectric constant. One connnon procedure for detennining dielectric constants is by using a Kramers-Kronig analysis of spectroscopic reflectance data [39]. This method suffers from the series-tennination error as well as the difficulty of making corrections for the presence of overlayer contaminants. The ellipsometry method is for the most part free of both these sources of error and thus yields the most accurate values to date [39]. 

Its purpose is twofold first of all to prevent any particles of the analysis sample, which is to be added next, from percolating through the coarse porous w ire-form " copper oxide and so into that portion of the tube heated by the furnace and secondly as a heat insulator, to present the sample being heated too rapidly by the nearby furnace. Both these safeguards are required, as otherwise some portion of the sample would be decomposed as soon as the furnace was sw-itched on the nitrogen so produced would be carried away during the initial sweeping of the air out of the tube with the carbon dioxide stream, and would not be collected. Low results w ould thus be obtained. 

Electron Beam Techniques. One of the most powerful tools in VLSI technology is the scanning electron microscope (sem) (see Microscopy). A sem is typically used in three modes secondary electron detection, back-scattered electron detection, and x-ray fluorescence (xrf). AH three techniques can be used for nondestmctive analysis of a VLSI wafer, where the sample does not have to be destroyed for sample preparation or by analysis, if the sem is equipped to accept large wafer-sized samples and the electron beam is used at low (ca 1 keV) energy to preserve the functional integrity of the circuitry. Samples that do not diffuse the charge produced by the electron beam, such as insulators, require special sample preparation. 

Analysis of insulation failures of an HT motor at a thermal power station 10/241... 

Installation of bearings and pulleys Important checks at the time of commissioning Maintenance of electric motors and their checks Maintenance of bearings General problems in electric motors and their remedy Winding temperature measurement at site Analysis of insulation failures of an HT motor at a thermal power station... 

Sample requirements Solid conductors and coated insulators typically 3 mm in diameter and < 200 nm thick at the analysis point for imaging and EDS, but < 50 nm thick for EELS... 

Sample conductivity Conductors and semiconductors direct analysis insulators (>10 (ohm-cm) ) pulverize and mix with a conductor... 

If the sample is an insulator there are still methods by which it can be studied in the instrument. The simplest approach is to coat it with a thin (10-nm) conducting film of carbon, gold, or some other metal. In following this approach, care must be taken to avoid artifacts and distortions that could be produced by nonuniform coatings or by agglomeration of the coating material. If an X-ray analysis is to be... 

In quadrupole-based SIMS instruments, mass separation is achieved by passing the secondary ions down a path surrounded by four rods excited with various AC and DC voltages. Different sets of AC and DC conditions are used to direct the flight path of the selected secondary ions into the detector. The primary advantage of this kind of spectrometer is the high speed at which they can switch from peak to peak and their ability to perform analysis of dielectric thin films and bulk insulators. The ability of the quadrupole to switch rapidly between mass peaks enables acquisition of depth profiles with more data points per depth, which improves depth resolution. Additionally, most quadrupole-based SIMS instruments are equipped with enhanced vacuum systems, reducing the detrimental contribution of residual atmospheric species to the mass spectrum. 

Laser ionization mass spectrometry or laser microprobing (LIMS) is a microanalyt-ical technique used to rapidly characterize the elemental and, sometimes, molecular composition of materials. It is based on the ability of short high-power laser pulses (-10 ns) to produce ions from solids. The ions formed in these brief pulses are analyzed using a time-of-flight mass spectrometer. The quasi-simultaneous collection of all ion masses allows the survey analysis of unknown materials. The main applications of LIMS are in failure analysis, where chemical differences between a contaminated sample and a control need to be rapidly assessed. The ability to focus the laser beam to a diameter of approximately 1 mm permits the application of this technique to the characterization of small features, for example, in integrated circuits. The LIMS detection limits for many elements are close to 10 at/cm, which makes this technique considerably more sensitive than other survey microan-alytical techniques, such as Auger Electron Spectroscopy (AES) or Electron Probe Microanalysis (EPMA). Additionally, LIMS can be used to analyze insulating sam-... 

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