Precise Cross Section Research Articles

Technique for preparation of precise wafer cross sections and applications to electron beam lithography of poly(methylmethacrylate) resist

We have developed a method of cross-sectioning silicon wafers with high placement precision. It is implemented by using optical lithography and deep plasma high aspect ratio etching of a thin line, which is used as the breaking axis. This technique is then applied to cross-sectional scanning electron microscopy (SEM) studies of sub-50 nm electron beam lithography in (poly)methylmethacrylate resist. We also report the development of a process for protecting the resist during SEM examination.

GENEVE: a Montecarlo generator for neutrino interactions in the intermediate energy range

GENEVE is a MonteCarlo code developed during the last few years inside the ICARUS Collaboration. It describes neutrino interactions on nuclear target in the “intermediate energy range” and therefore is well suited for simulation of atmospheric neutrino scattering. We provide here few indications about the models adopted for the simulation of quasi-elastic interactions and of scattering processes proceeding via nucleon resonances excitation and decay. The code has been tested with comparisons with available data and an overall agreement turns out to be achieved. A gradual upgrade of the code is indeed necessary, according to many indications, reviewed during this Workshop, from more recent theoretical developments and experimental hints. More in general, the definitive assessment of a canonical MonteCarlo code for neutrino physics (in the intermediate energy range) has been identified as one of the most urgent task for a fully comprehensive understanding of the neutrino oscillation phenomenon. We believe that the only way to proceed relies on the forthcoming results of present and future generations of experiments, performed with best suited, available technologies, aiming to precise neutrino cross section measurements.

High Precision Measurements of Spectrum Averaged Total Neutron Cross Section for Chromium

The intense neutron beams formed by composite neutron filters at reactor horizontal channels give the fluxes of about 106 – 108 neutron/cm2s at the fixed neutron energies and it makes it possible to measure the neutron cross sections with accuracy better than 0.1%.The need of such measurements is formulated in the document The NEA High Priority Nuclear Data Request List, May 1998 (for Cr in the energy range 0.1 keV – 5 MeV and for Cr-52 in 10 eV – 20 MeV). Cr is one of the important structural materials for NPP and research reactors just as for fusion technology. These precise cross section data may be used also in the practice of work for evaluated nuclear data libraries. Now the discrepancies in total cross section for Cr in evaluated nuclear data libraries are in the range 3 – 50% for energies up to 200 keV.At Kyiv Research Reactor now we have the set of neutron filters for the fixed energies in the range 0 – 600 keV, here we present the transmission measurements at the energies 24.3 and 58.8 keV for Cr and Cr-52 (99.3% enrichment) samples.The results of measurements are presented together with the analysis of the known previous experimental data and the evaluated nuclear data from ENDF/B-VI, JEF-2.2, JENDL-3.2, BROND-2 and CENDL-2 libraries.

Precise photoabsorption cross sections of Ne and Xe

Precise photoabsorption cross sections for Ne and Xe in the soft X-ray region are measured using a multi-electrode ion chamber. The photoabsorption cross section of Ne is very close to the previously reported data. However, there are some discrepancies in the photoabsorption cross section of Xe between the present results and the previously reported data.

Branching Fraction Measurements of the SM Higgs with a Mass of 160 GeV at Future Linear e+e? Colliders

Assuming an integrated luminosity of 500 fb−1 and a center-of-mass energy of 350 GeV, we examine the prospects for measuring branching fractions of a Standard Model-like Higgs boson with a mass of 160 GeV at the future linear e+e−collider TESLA when the Higgs boson is produced via the Higgsstrahlung mechanism, e+e− → HZ. The Higgs boson mass chosen close to the W pair threshold covers a mass regime with complicated background structures. We study in detail including some detector responds the precisions achievable for the branching fractions of the Higgs boson into WW(*), ZZ* and \(b{\bar b}\), whereas the measurement of BF(H → γ γ) remains a great challenge. Expectations for the total Higgs width are discussed using either the BF(Z → ZZ*) measurement of this study and the expected error for the inclusive Higgsstrahlung cross section or in addition the precise cross section expected for the weak boson fusion process, e+e− → v\({\bar v}\) H, or W,Z-universality.

Critical review of [formula omitted] scattering

Nucleon-antinucleon scattering experiments carried out at LEAR are briefly reviewed. Differential cross-section data of high accuracy are now available at many energies, and for the first time also analysing power data and some data on spin correlation parameters. Excellent fits to the N N data base have been performed by the Nijmegen group, both with a phase-shift analysis and with a coupled-channel potential model. The high precision cross section data from experiment PS206 have allowed a determination of the charged pion-nucleon coupling constant by a simple extrapolation to the pion pole. A phenomenological analysis of the line-reversed reaction np → pn and p p → n n data is ongoing, to single out the basic dynamical features of the long-range part of the interaction and possibly experimental manifestations of the G-parity rule.

Production Cross Sections of Fragments from Beams of 400–650 MeV per Nucleon9Be,11B,12C,14N,15N,16O,20Ne,22Ne,56Fe, and58Ni Nuclei Interacting in a Liquid Hydrogen Target. I. Charge Changing and Total Cross Sections

We have measured the charge changing cross sections from 10 individual beams of isotopes from 8 different nuclei between Be and Ni which were accelerated to energies from 400-650 MeV nucleon-1 at the SATURNE Accelerator in France in 1993 and 1994. These nuclei interacted in a 1.52 g cm-2 thick liquid hydrogen target and the fragments were observed. This is the first use of a pure hydrogen target to measure cross sections that has a thickness approximating the amount of hydrogen traversed by cosmic rays in our Galaxy. Several of the beam charges such as 9Be,11B,15N, and 22Ne have not had their fragmentation cross sections measured previously. The cross sections from the 12C,14N,16O,20Ne,56Fe, and 58Ni beams are compared with earlier measurements by our group using a CH2 - C target subtraction technique to determine the hydrogen cross sections. The overall agreement between the new measurements and the earlier measurements using CH2 - C subtraction is excellent with a systematic consistency between measurements of 3%-5%. Using these new cross sections the predictions of both the B/C and Z = (21-23)/Fe ratios at ~1 GeV nucleon-1 now agree with HEAO measurements to ~1%-2%, thus obviating the need for truncation of the exponential path length distribution path length distribution that is expected from uniform propagation models. Also, these new charge changing cross sections along with the isotopic cross sections reported in paper two of this series, define the production of cosmic-ray beryllium and boron nuclei in the galaxy and also the secondary isotopes 10Be,13C,14N,15N,18O, and all of the Fe secondary isotopes to a level of precision of 3%-5% or better. These cross sections are important for determining the abundance of these rare isotopes and others in the cosmic-ray sources as well as tracing the detailed propagation history of cosmic rays in the Galaxy. These measurements also provide high precision cross sections for the study of the nuclear physics of the interaction process.

Application of a Simple Ramsauer Model for Neutron Total Cross Sections

A companion paper presented arguments that support the applicability of a simple Ramsauer model to describe neutron total cross sections. Such a model yields a simple equation for the energy dependence of the cross section of a given nucleus and also allows extrapolation to nuclei of other A values. Fits of the Ramsauer form to very precise total cross sections recently measured over an extended energy range are presented. Very good fits are obtained for neutron energies between 6 and 60 MeV, suggesting that this approach will be useful for estimating cross sections in cases where experimental data are unavailable. Extension of this model to 120 MeV was only moderately successful.

Direct Imaging of Device Characteristics In a Focused ion Beam System

Abstract A great deal can be learned about integrated circuits (ICs) and microelectronic structures simply by imaging them in a focused ion beam (FIB) system. FIB systems have evolved during the past decade from something of a curiosity to absolutely essential tools for microelectronics design verification and failure analysis. FIB system capabilities include localized material removal, localized deposition of conductors and insulators, and imaging. A major commercial driver for FIB systems is their usefulness in the design debugging cycle by (1) rewiring ICs quickly to test design changes and (2) making connection to deep conductors to facilitate electrical probing of complex ICs. FIB milling is also used for making precision cross sections and for TEM sample preparation of microelectronic structures for failure analysis and yield enhancement applications.

Application of Electron Microscopy Towards the Analysis of Submicron Particles and Microcorrosion

AbstractSmall particles in ULSI devices are one of the key causes for affecting device yield. This is especially true since modern devices are shrinking in all dimensions and the critical size for ‘killer’ particles is also shrinking. It is increasingly challenging to identify the root cause of particle contamination in terms of locating and identifying the particles. A precision cross section through the particles is required to be able to identify at which processing step the particles occurred and an energy dispersive spectroscopy (EDS) microanalysis usually helps identify the source. This paper focuses on the methodology for carrying out submicron defect and particle analysis. In addition to processing knowledge, it demonstrates the importance of techniques such as scanning electron microscopy (SEM), EDS, and focused ion beam (FIB). The analysis of microcorrosion observed after third metal deposition, and submicron titanium particles after metal etch are used as vehicles to illustrate the procedure of submicron particle analysis.

Failure Analysis Using Voltage Contrast and Ebic

AbstractAs ULSI device critical dimensions continue to shrink to submicron sizes, electron microscopy techniques such as electron beam induced current (EBIC) and voltage contrast are finding more applications towards pinpointing failure sites for subsequent cross sectioning or deprocessing. In addition to the traditional use of EBIC for junction delineation, EBIC has been applied to locate leakage sites in capacitor structures and silicon-on-insulator (SOI) devices as well. Similarly, voltage contrast has been applied to identify single or multiple opens in via chains which consist of thousands of vias. In addition to a brief revisit of the basic principles of EBIC and voltage contrast, focus will be placed on the application of EBIC and voltage contrast in failure analysis of semiconductor devices. Examples of using voltage contrast combined with precision cross section focused ion beam (XFIB) for identifying the failure mechanism of 0.8μm vias will be presented. Also, the use of EBIC for identifying leakage sites in SOI and bipolar devices and subsequent FIB/scanning electron microscopy (SEM) analysis will be presented.

The Preparation of Submicron Precision Cross Sections by Dimpling With A ‘Flatting Tool’

AbstractThe complex materials systems in VLSI devices require specialized preparation techniques for TEM microstructural analysis. For this purpose, it is desirable to obtain electron transparency in all material layers from the oxides used in dielectrics to refractory metals such as tungsten. The primary advantage of dimpling these materials is that ideal specimens are obtained for low angle ion milling. By dimpling both sides of the cross section with a padded flatting tool, a thicker specimen of 130μm at the outer rim of the 3mm disc is produced that narrows to the 125nm thickness fringes in the center. These samples do not require a copper support grid, thereby allowing for a lower milling angle of 2.5 degrees on both sides of the specimen. This technique provides a cross section that is electron transparent in all layers without the loss of oxides due to differential thinning rates of various materials at higher milling angles.It is generally thought that precision thinning through a submicron feature is not possible on the dimpler. However, a simple step-by-step procedure for this technique will be demonstrated and discussed.

Reevaluation of the hadronic contribution to alpha (MZ2).

We reevaluate the hadronic part of the electromagnetic vacuum expectation value using the standard dispersion integral approach that utilizes the hadronic cross section measured in $\ee$ experiments as input. Previous analyses are based upon point-by-point trapezoidal integration which does not treat experimental errors in an optimal way. We use a technique that weights the experimental inputs by their stated uncertainties, includes correlations, and incorporates some refinements. We find the five-flavor hadronic contribution to the fractional change in the electromagnetic coupling constant at $q^2=M_Z^2$, $\Delta\alpha(MZ)$, to be $0.02752\pm0.00046$, which leads to a value of the electromagnetic coupling constant, $\alpha^{-1}(M_Z^2) = 128.96\pm0.06$. [This is an updated version of SLAC-PUB-6710 (hep-ph/9411353) which fixes a small bias in the fitting procedure (1/3 of the change) and incorporates a new and precise cross section measurement near charm threshold (2/3 of the change).]

High Temperature Doppler Effect Experiment for 238U at FCA, (I)

The experimental device for Doppler effect measurement was developed for the Fast Critical Assembly of Japan Atomic Energy Research Institute. The Doppler effect up to 1,500°C can be measured with this device. The experimental data is to be used for evaluating and improving the calculation method of the Doppler effect in higher temperature range. The measurement technique is based on a reactivity worth measurement with a heated sample. The device is made of tungsten for the high temperature parts and stainless steel for the other structural parts. The measurements were carried out in a mock-up core of an oxide-fueled fast reactor. In the analysis of the experimental data, the Doppler reactivity worth was calculated by a first order perturbation theory and JENDL-3.2 library. A collision probability cell code with ultra-fine group structure, PEACO-X, was used to obtain the precise effective cross sections in a pin cell model of the Doppler sample. The calculation underestimates Doppler effect by about 5% in high temperature range. The Doppler effect above 1,500°C was estimated by the extrapolation of the measured data below this temperature. When the calculated and extrapolated Doppler reactivity worths at 2,000°C were compared, a good agreement between them was obtained. The significant improvement of calculation reliability of the Doppler effect in the higher temperature range was achieved by this experiment.

High Temperature Doppler Effect Experiment for 238U at FCA, (I). Reactivity Worth Measurement with a Small Heated Sample up to 1,500.DEG.C..

The experimental device for Doppler effect measurement was developed for the Fast Critical Assembly of Japan Atomic Energy Research Institute. The Doppler effect up to 1,500°C can be measured with this device. The experimental data is to be used for evaluating and improving the calculation method of the Doppler effect in higher temperature range. The measurement technique is based on a reactivity worth measurement with a heated sample. The device is made of tungsten for the high temperature parts and stainless steel for the other structural parts. The measurements were carried out in a mock-up core of an oxide-fueled fast reactor.In the analysis of the experimental data, the Doppler reactivity worth was calculated by a first order perturbation theory and JENDL-3.2 library. A collision probability cell code with ultra-fine group structure, PEACO-X, was used to obtain the precise effective cross sections in a pin cell model of the Doppler sample. The calculation underestimates Doppler effect by about 5% in high temperature range.The Doppler effect above 1,500°C was estimated by the extrapolation of the measured data below this temperature. When the calculated and extrapolated Doppler reactivity worths at 2,000°C were compared, a good agreement between them was obtained. The significant improvement of calculation reliability of the Doppler effect in the higher temperature range was achieved by this experiment.

Improved Neutronics Model of the High Flux Isotope Reactor

An improved core physics model of the High Flux Isotope Reactor (HFIR) has been developed and evaluated by comparing calculational results with experimental results and also with calculational results obtained with earlier models. Eleven-group and 4-group cross-section libraries that are problem specific, collapsed, and weighted for the HFIR are generated from the 39-group Advanced Neutron Source Reactor cross-section library (ANSL-V general-purpose neutron library), which is based on ENDF/B-V. A diffusion theory-based procedure to analyze the static neutronics of the reactor is developed. Precise cross sections that take fuel loading variations (not considered in previous work) into account are also generated and implemented into an improved R-Z geometry model of the reactor. Point-by-point power densities are calculated using a detailed mesh structure. The results show that the improved model and procedure developed in this work give good agreement with experiments at interior locations with significant deviations at the outer boundary of the reactor core, which is near the control blades. More importantly, the improved model and procedure provide better overall agreement with experimental results than earlier models.

Near threshold photoproduction of eta mesons off the proton.

We have measured precise total and differential cross sections for the reaction $\ensuremath{\gamma}p\ensuremath{\rightarrow}p\ensuremath{\eta}$ from threshold to 790 MeV at the MAMI accelerator in Mainz with the neutral meson spectrometer TAPS. Resonance parameters of the ${S}_{11}$(1535) resonance and the electromagnetic coupling $\ensuremath{\gamma}p\ensuremath{\rightarrow}{S}_{11}$ have been extracted from the data. Contributions from the ${D}_{13}$(1520) resonance to $\ensuremath{\eta}$ photoproduction in the threshold region have been identified for the first time via interference terms in the angular distributions.

Precise relative cross sections for np scattering

We present data on the differential cross section for neutron-proton scattering for an incident neutron energy of 67 MeV. These data allow a precise determination of the 1P 1 phase which, in phase-shift analyses, is strongly correlated with the S-D amplitude which we are measuring via different observables.

On estimating the top quark mass from global analyses ofe + e − collision data

A study is undertaken to determine how to best extract the top quark massm t within the Minimal Standard Model (MSM) using a global fit to a variety of processes (including wide-angle Bhabha scattering) ine + e − collisions near theZ which should be measured in the coming years. Experimental cuts are accommodated as an integral part of the analysis. It is advantageous to use the collinear radiation approximation and to cut data in rapidity, center-of-mass polar angle and minimum final state invariant mass squared,s′. This avoids the need for the largest Monte Carlo acceptance correction to the data. Further, high precision cross section, calculations, (which include all one-loop electroweak and QED effects, certain higher-order improvements and perturbative QCD corrections as well as exponentiated soft and collinear photon radiation) then no longer require a Monte Carlo. This results in a speedup factor of at least fifty thousand (>5×104) in EXPOSTAR. The data (corrected only for detector cracks, resolution and small non-collinear radiation effects) can therefore be fit quickly and directly forM z ,m t ,m Higgs and αstrong without recourse to unphysical intermediate quantities (weak mixing angles, running couplings, partial widths, κ*, etc.) Determination ofm t could be as precise as ±15 GeV (and another±20 GeV fromm Higgs) at the end of LEP running in 1991. Longitudinally polarized beams with very small polarization error could give an error onm t smaller, by a factor ≈4 for the same luminosity.

Forward nuclear glory in 12C+12C scattering.

Very precise elastic cross sections have been measured in a very forward angular range (up to 1.6\ifmmode^\circ\else\textdegree\fi{} laboratory) for the $^{12}\mathrm{C}$${+}^{12}$C system at six energies not too far above the Coulomb barrier. From these data the symmetrized nuclear scattering amplitude ${\mathit{f}}_{\mathit{N}}^{\mathit{s}}$(\ensuremath{\theta}) for small angles and the total reaction cross section ${\mathrm{\ensuremath{\sigma}}}_{\mathit{R}}$ could be derived making use of the generalized optical theorem for charged particles. It was found that \ensuremath{\Vert}${\mathit{f}}_{\mathit{N}}^{\mathit{s}}$(0)\ensuremath{\Vert} exceeds zero significantly in all cases investigated. This means that a forward nuclear glory exists in the $^{12}\mathrm{C}$${+}^{12}$C scattering. This is the first time that evidence for a forward nuclear glory is deduced from experimental data.