Electron Beam Probe Research Articles

Donor nonuniformity in undoped and Si doped n-GaN prepared by epitaxial lateral overgrowth

Local donor concentrations were measured in the regions of lateral overgrowth and in the normal vertical growth regions of n-GaN films prepared by epitaxial lateral overgrowth (ELOG). The films were doped with Si to various concentrations. The local donor densities were determined from measurements of the collection efficiency dependence of the electron beam induced current (EBIC) on the energy of the probing electron beam. This dependence was compared with the results of theoretical modeling using the local donor density and diffusion length of charge carriers as fitting parameters. The results show that the donor concentration in the ELOG regions is systematically more than two times lower than the concentration in the vertical growth regions in the gaps of the SiO2 mask used for selective growth. The observed difference is ascribed to the anisotropy of the Si incorporation efficiency. Comparison of these EBIC results with the results of capacitance-voltage profiling obtained on large area Schottky diodes shows that the latter yield the donor concentration close to the concentration in the laterally overgrown regions.

Microstructure and wear properties of Fe–VC–Cr 7C 3 composite coating on surface of cast steel

An Fe–VC–Cr 7C 3 composite coating on the surface of cast steel was produced by a novel metal-coated casting technique. The microstructure and wear properties of the product were studied by means of X-ray diffraction, electron beam probe, scanning electron microscopy, and wear testing. The results show that the composite coating consisted of VC and Cr 7C 3 as the reinforcing phases and α-Fe as the matrix. The composite coating was metallurgically bonded to the cast steel substrate. The quantity of VC and Cr 7C 3 carbides decreased gradually from the top surface of the composite coating to the cast steel substrate. The Fe–VC–Cr 7C 3 composite coating displayed excellent wear-resistance under dry sliding wear test conditions.

Real-time determination of electron-beam probe shape using an in situ fiducial grid

Electron-beam probe shape is typically determined by imaging a known or quasirandom target; however, neither standard targets nor two-dimensional image acquisition and processing are suitable for real-time probe characterization during lithographic exposures. Here a new technique for continuously monitoring probe shape is proposed and evaluated. Fourier analysis of the signal generated by an in situ fiducial grid allows estimation of the x and y widths and rotation of a Gaussian beam. The grid itself is rotated with respect to the beam deflection axes to allow real-time estimation of two-dimensional probe shape from a one-dimensional line scan across the grid. Monte Carlo simulations of beam parameter variances versus signal-to-noise ratio reveal regions of operation where the algorithm’s precision is limited by either noise or grid geometry. Experiments using a 1μm period grid to estimate probe shape as a function of defocus demonstrate the effectiveness of the new approach.

Polarization dependence in ELNES: Influence of probe convergence, collector aperture and electron beam incidence angle

The differential scattering cross section in electron energy loss near edge spectroscopy (ELNES) generally depends on the orientation of the Q wave vector transferred from the incident electron to an atomic core electron. In the case where the excited atom belongs to a threefold, fourfold or sixfold main rotation axis, the dipole cross section depends on the angle of Q with respect to this axis. In this paper, we restrict to this situation called dichroism. Furthermore, if we take into account the relativistic effects due to the high incident electron velocity, this dipole cross section also depends on the angle of Q with respect to the electron beam axis. It is due to these dependences that the shape of measured electron energy loss spectra varies with the electron beam incidence, the collector aperture, the incident beam convergence and the incident electron energy. The existence of a particular beam incidence angle for which the scattering cross section becomes independent of collection and beam convergence semi-angles is clearly underscored. Conversely, it is shown that EELS spectra do not depend on the beam incidence angle for a set of particular values of collection and convergence semi-angles. Particularly, in the case of a parallel incident beam, there is a collection semi-angle (often called magic angle) for which the cross section becomes independent of the beam orientation. This magic angle depends on the incident beam kinetic energy. If the incident electron velocity V is small compared with the light velocity c, this magic angle is about 3.975 θ E ( θ E is the scattering angle). It decreases to 0 when V approaches c. These results are illustrated in the case of the K boron edge in the boron nitride.

Interaction between Shock Wave and Boundary Layer in Nonequilibrium Hypersonic Rarefied Flow

An experimental study of the interaction between a shock wave and a boundary layer over a flat plate with a sharp leading edge in hypersonic rarefied gas flow is presented. Experiments in a low-density wind tunnel using an electron beam probe were conducted at the Shock Wave Laboratory, RWTH Aachen, Germany. Rotational temperatures for stagnation temperatures of T0=670∼1000 K and Kn=0.024∼0.028 based on a reference length of 0.05m were calculated using Muntz’s method and Robben and Talbot’s method. The domain of quasi two-dimensional flow over the plate was determined from three-dimensional rotational temperature measurements. Nonequilibrium between translational and rotational temperatures was observed near the leading edge, and the experimental rotational relaxation length explains the rotational collision number of 2∼4.

Experimental and Numerical Study of Hypersonic Rarefied Gas Flow over Flat Plates

An experimental study of the hypersonic rarefied gas flow over a flat plate with a sharp leading edge is presented. Experiments in a low-density wind tunnel using an electron beam probe were conducted at the Shock Wave Laboratory, RWTH Aachen, Germany. Rotational temperatures for stagnation temperatures of To = 670 ∼ 1000 K and Kn = 0.024 ∼ 0.028 based on a reference length of 0.05 m were calculated by Muntz's method and by Robben and Talbot's method. The domain of quasi-two-dimensional flow over the plate was determined from three-dimensional rotational temperature measurements. A direct simulation Monte Carlo (DSMC) method is applied to obtain a nonequilibrium state for the rarefied gas flow over the flat plate.

Electron imaging of charge-separated field on a copper film induced by femtosecond laser irradiation

An instantaneous charge-separated field, built up at the femtosecond-laser-irradiated surface of a copper film, was observed by time-resolved electron imaging using an energy-chirped electron probe-beam. The probe beams with effective energies of 170keV were generated by intense femtosecond laser irradiation onto a molybdenum target at an intensity of 1017W∕cm2. From the deflection of the probe electrons, the electric field was estimated to be 1.5MV∕m at a pump-laser intensity of 1015W∕cm2.

Diagnostics for intense heavy-ion beams in the HIF-VNL

Modern diagnostic techniques provide detailed information on beam conditions in injector, transport, and final focus experiments in the HIF-VNL. Parameters of interest include beam current, beam energy, transverse and longitudinal distributions, emittance, and space charge neutralization. Imaging techniques, based on kapton films and optical scintillators, complement and, in some cases, may replace conventional techniques based on slit scans. Time-resolved optical diagnostics that provide 4-D transverse information on the experimental beams are in operation on the existing experiments. Current work includes a compact optical diagnostic suitable for insertion in transport lines, improved algorithms for optical data analysis and interpretation, a high-resolution electrostatic energy analyzer, and an electron beam probe. A longitudinal diagnostic kicker generates longitudinal space-charge waves that travel on the beam. Time of flight of the space-charge waves and an electrostatic energy analyzer provide an absolute measure of the beam energy. Special diagnostics to detect secondary electrons and gases desorbed from the wall have been developed.

Interaction between a Shock Wave and a Boundary Layer in a Nonequilibrium Hypersonic Rarefied Flow (5th Report, Nonequilibrium of Rotational Temperature in a Flow over a Plate)

An experimental study of the interaction between shock wave and boundary layer over a flat plate with a sharp leading edge in hypersonic rarefied gas flow is presented. Experiments in a low density wind tunnel using an electron beam probe were conducted at the Shock Wave Laboratory, RWTH Aachen, Germany. Rotational temperatures for stagnation temperatures of T0=670-1000K and Kn=0.024-0.028 based on a reference length of 0.05m were calculated by Muntz's method and by Robben and Talbot's method. The domain of quasi two-dimensional flow over the plate was determined from three-dimensional rotational temperature measurements. Nonequilibrium between translational and rotational temperatures was observed near the leading edge, and the experimental rotational relaxation length explains the rotational collision number of 2-4.

Electron beam probe quantization of compound composition: surface phases and surface roughness

In electron probe beam micro-analysis (EPMA), the electron accelerating voltage decides the penetration depth of the probe beam therefore the voltage dependence of the characteristic X-ray emission intensities reflects the composition depth distribution. This effect can be utilized to determine an accurate composition value for the matrix and to identify other phases. As the measured emission intensity is a convolution of the entire probed depth, a parameter fitting procedures using a computer was developed to deconvolute measured spectra of accelerating voltage dependent data. Using this method, a surface phase segregated on CuGaSe 2 epi-layers grown by molecular-beam epitaxy under Cu-excess conditions was detected and found to be Cu 3Se 2. Oxidation of CuInSe 2 or CuGaSe 2 film surfaces was also detected by EPMA. The thickness of the natural oxide layers evaluated by this technique was several nanometers. The weakest point in EPMA analysis is its sensitivity to specimen surface roughness. A theoretical estimation of surface roughness effects matched actual data well. This result suggests possible corrections for measured values on rough surfaces.

Comparative study of electron beam–gas interaction in an SEM operating at pressures up to 300 Pa

The effects of three different gas environments formed by pure argon, helium and nitrogen with variable pressures up to 300 Pa inside the specimen chamber of a scanning electron microscope on the electron beam parameters were investigated and compared using Monte Carlo calculations. The calculations show that the skirt of the electron beam probe is nearly independent of pressure in the case of helium, which is also supported by experimental evidence. Both theoretical simulation and experimental facts indicate helium as the environment of choice in specimen chambers for minimizing the effect of beam–gas interactions.

Energy dispersive spectroscopy analysis of aluminium segregation in silicon carbide grain boundaries.

The aluminium distribution in polycrystalline SiC hot-pressed with aluminium, boron and carbon additives was studied using X-ray energy-dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The Al excess in homophase SiC grain boundary films was determined, taking into account dissolved Al in the SiC lattice. In the spot-EDS analysis, an electron beam probe with a calibrated diameter was formed, and the total beam-specimen interaction volume was defined, taking the beam spreading through crystalline TEM foil into consideration. EDS spectra were collected from regions containing intergranular films and adjacent matrix grains, respectively. A theoretical treatment was presented and experimental errors were estimated, with a further discussion about the effects of foil thickness. Experimental examples are given, followed by statistical EDS analyses for grain boundary films in SiC samples hot-pressed with increased amounts of Al additions. The results demonstrated a substantial Al segregation in the nanometer-wide intergranular films in all samples. Al additions higher than 3 wt% saturated the Al concentrations in SiC grains and in grain boundary films. The effect of foil thickness, and the parameters for determining the optimum incident beam diameter in the EDS analysis are discussed.

Field emission noise caused by capacitance coupling ESD in AMR/GMR heads

We found field emission between the shield and the disk in AMR/GMR heads that was induced by a high voltage of the write driver. This paper discusses the mechanism of noise generation obtained using spin-stand, an electron beam probe measurement method and SPICE simulation. The source of noise in field emission is the current passing through the GMR element generated by capacitance coupling between the shield and the electrode. To prevent ESD/EOS damage to AMR/GMR heads, the effect of capacitance coupling between the GMR element and the write coil must be taken into account in the design of the AMR/GMR head structure for hard disk drives.

High-resolution energy-dispersive x-ray spectroscopic analysis of ultrathin ion diffusion barriers using microcalorimetry

The advent of microcalorimetry for x-ray detectors holds the promise for high-resolution compositional microanalysis applicable to nanometer-scale devices and structures. To demonstrate this capability, microcalorimeter-based energy dispersive x-ray spectroscopy (EDS) has been used to analyze ultrathin TaSiN films under development as ion diffusion barriers in sub-0.1 μm integrated circuit interconnect structures. Microanalysis of TaSiN films has been carried out using microcalorimetry-based EDS for comparison with similar data acquired using conventional Si(Li) EDS detectors. The elimination of elemental peak overlaps provided by the improved energy resolution of the microcalorimeter x-ray detector is demonstrated for TaSiN EDS spectra from films as thin as 3.5 nm. In addition, variation of the electron probe beam energy is examined to reduce the x-ray generation volume relative to the TaSiN film thickness. It is shown that microcalorimetery-based EDS is a potentially powerful technique for the characterization/metrology of ultrathin barrier films used for microelectronics, with x-ray energy-resolving capabilities similar to techniques such as wavelength dispersive spectroscopy.

Time-resolved structural study of low-index surfaces of germanium near its bulk melting temperature

The structure of the low-index surfaces of germanium near its bulk melting temperature is investigated using 100-ps time-resolved reflection high-energy electron diffraction. The surface is heated by 100-ps laser pulses while a synchronized electron beam probes the structure. Ge(111) was observed to remain in its incomplete melting structure up to at least ${T}_{m}+134\ifmmode\pm\else\textpm\fi{}40\mathrm{K}$ when heated by a 100-ps laser pulse. Both the Ge(100) and Ge(110) surfaces are observed to melt near the bulk melting temperature when heated with 100-ps laser pulses. Because of the low-diffraction intensity-to-background ratio at high temperatures and because of the temperature uncertainty in the time-resolved experiments, we are unable to accurately identify the melting point of Ge(100) and Ge(110) when heated with a 100-ps laser pulse. The results, however, favor the lack of surface superheating of Ge(100) and, to some extent, Ge(110). The superheating of the incomplete melting state of Ge(111) could be due to the metallization of the top germanium bilayer and its interaction with the solid underneath causing an energy barrier sufficient to allow for transient surface superheating.

Observation of the internal waveforms in high-speed high-density LSIs using an EOS prober

Electron beam (EB) probing has been used to observe the internal waveforms in ULSLs. However, as the speed of LSIs increases and their power consumption decreases, the temporal and voltage resolution of EB probing is going to be inadequate for measuring these waveforms. Electro-optic sampling (EOS) probing is expected to overcome this limitation, provided its spatial resolution can be improved. In this paper, forming a via on the interconnection under test is proposed for practically improving spatial resolution. The effectiveness of this method and the dependence of the detected signal level on testing pad area are clarified by simulation. To verify these results, vias are formed in ECL SRAMs by focused ion beam trimming, and waveforms with frequency as high as 100 MHz and swing as small as 30 mV are successfully observed. Using this technique, the dependence of the detected signal level on testing pad area is verified, and it is confirmed that the amplitude change below 10 mV and the delay time below 100 ps can be measured. With the improved spatial resolution, EOS probing enables us to observe high-frequency and small-swing waveforms even in high-density fine interconnections. In future, this technology will be crucial for observing internal waveforms in LSIs.

Development of combinatorial PLD-STM system for the quick nano-fabrication and evaluation

AbstractA combinatorial PLD-STM system has been developed for quick nano-fabrication and evaluation of epitaxial thin films and catalysts. Through a gate valve, a combinatorial nano-materials library fabricated in a PLD chamber can be transferred to a surface analysis chamber equipped with LEED and STM. The LEED pattern and atomically resolved STM image for systematically varied samples in the library are measured by locating one sample to another at the electron beam and STM probe position. In this way, we have quickly elucidated the initial growth process of SrO on SrTiO3(001) as well as surface structures of transition metal deposited TiO2 anatase. The combinatorial PLD-STM system has been verified to be very efficient technique for the exploration and optimization of nano-materials.

Laser Voltage Probe (LVP): A Novel Optical Probing Technology for Flip-Chip Packaged Microprocessors

Abstract Laser voltage probing (LVP), an IR-based technique, facilitates through-silicon signal waveform acquisition and high frequency timing measurements from active p-n junctions on CMOS ICs. The ICs can be in flip-chip as well as wire-bond packages with backside access to the IC. As the article explains, LVP significantly improves silicon debug and failure analysis throughput time compared to electron-beam probing because it eliminates the need for backside trenching and probe-hole generating operations.

Beam electron microprobe

A beam profile monitor based on the deflection of a probe electron beam by the electric field of a stored, electron-cooled proton beam is described and first results are presented. Electrons were transported parallel to the proton beam by a uniform longitudinal magnetic field. The probe beam may be slowly scanned across the stored beam to determine its intensity, position, and size. Alternatively, it may be scanned rapidly over a narrow range within the interior of the stored beam for continuous observation of the changing central density during cooling. Examples of a two dimensional charge density profile obtained from a raster scan and of a cooling alignment study illustrate the scope of measurements made possible by this device.

Ultrashallow p +-n junctions in Si(111): Electron-beam diagnostics of the surface region

Ultrashallow p+-n junctions fabricated in Si(111) are investigated by low-and intermediateenergy electron-beam probing of the surface region in order to determine how the crystallographic orientation of the silicon films affects the mechanisms for nonequilibrium diffusion of boron. A comparative study is made of p+-n junctions made on both (111) and (100) silicon with regard to how the irradiation-induced conductivity depends on the energy of the primary electron beam, and also its distribution with area. Using this method, it is possible to determine how the probability of an electron-hole pair being separated by the electric field of the Si(111) and Si(100) p+-n junctions varies with depth into the crystal, which experiments show is different, depending on whether diffusive motion of impurities is dominated by the kick-out or dissociative-vacancy mechanisms. It was found that for boron in silicon the kick-out type of diffusion mechanism is strongly enhanced in the [111] crystallographic direction, whereas diffusion in the [100] direction is primarily driven by vacancy mechanisms. It is shown that collection of nonequilibrium carriers in the p+-n junction field is strongly enhanced when the diffusion profile consists of certain combinations of longitudinal and transverse quantum wells.