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X‐ray scattering is a non‐destructive analytical technique capable of detecting electron density fluctuations in mesoporous and nanoporous structures. X‐ray methods have the potential to provide fully quantitative porosity analyses of open and closed pore structures. Specular x‐ray reflectivity (XRR) offers accurate measurement of thickness, density, and roughness of uniformly deposited thin films. Diffuse scattering techniques are also studied by manipulation of the scattering geometry and approximation of the average pore size and pore size distribution. Effects of refraction and reflection from the surface and buried interface are corrected via the Distorted Wave Born Approximation (DWBA). Distortion of the scattering profile due to slit smearing is also taken into account to obtain an accurate interpretation of diffuse scattering phenomena. Preliminary results for average pore size and pore size distribution of PECVD‐prepared SiCOH thin films with both open and closed pore structures are reported, and show good agreement with positron annihilation lifetime spectroscopy (PALS) data.

Sample preparation is a critical step in transmission electron microscopy (TEM) that significantly determines the quality of structural characterization and analysis of a specimen. In recent years, the accuracy and quality requirements for the preparation of TEM cross‐sections of nanoelectronic structures have drastically increased. Combining a focused low‐energy noble gas ion beam column with a FIB and a SEM column in a three beam system meets these requirements. It provides precise target preparation as well as minimum thickness and surface damage of the TEM sample.

In recent years, scatterometry has become one of the most commonly used methods for CD metrology. With decreasing structure size for future technology nodes, the search for optimized scatterometry measurement configurations gets more important to exploit maximum sensitivity. As widespread industrial scatterometry tools mainly still use a pre‐set measurement configuration, there are still free parameters to improve sensitivity. Our current work uses a simulation based approach to predict and optimize sensitivity of future technology nodes. Since line edge roughness is getting important for such small structures, these imperfections of the periodic continuation cannot be neglected. Using fourier methods like e.g. rigorous coupled wave approach (RCWA) for diffraction calculus, nonperiodic features are hard to reach. We show that in this field certain types of fieldstitching methods show nice numerical behaviour and lead to useful results.

Orientation imaging microscopy by electron backscatter diffraction (EBSD) has been used to examine grain size and crystallographic orientations of damascene Cu lines nominally 25 nm to 55 nm in width and 100 nm thick. These are the smallest structures reported to have been examined by EBSD to date. This application poses significant challenges in specimen preparation, data collection, and data analysis. Most lines were deposited on a Ta diffusion barrier, and one set had a Ti barrier. Overburden thicknesses of 120 nm, 240 nm, and 480 nm were available with the Ta diffusion barrier, but only the 120 nm overburden case was analyzed for the Ti diffusion barrier. The grain structure of the lines was predominantly bamboo. The distributions of grain lengths along individual lines had large standard deviations, ranging up to greater than the average grain size value. Print‐through of overburden grains into the grain structure of the lines was evident for all lines. Large grain sizes and a strong positive correlation between line width and grain size were seen for the case of the Ta barrier layer with 120 nm overburden thickness, but not for the thicker overburden cases. Specimen surface preparation of these lines was found to be much more demanding than for larger regions of copper films such as those that have been studied previously. For some lines, prepared according to the typical state of the art, we were able to find indexable diffraction signals from less than half of the 100 μm line length.

As the MOSFET SiO2‐based gate dielectric layer approaches its fundamental physical limits, the investigation of high‐k oxides is ongoing in order to determine which oxides can best continue the scaling of the MOSFET. HfO2 and hafnium silicates are leading candidates due to their relatively large band gaps, thermal stability in proximity to Si and relatively high dielectric constants. We have used a combination of x‐ray photoemission spectroscopy (XPS) and spectroscopic ellipsometry (SE) to measure the band offsets between the high‐k layers and the Si substrates. Shifts in band alignment that occur upon deposition of the HfO2 layer and annealing of the HfO2/SiO2/Si film stack will be discussed in light of XPS spectra. Non‐destructive compositional depth profiles constructed from angle resolved XPS data will also be presented and film thicknesses determined from them will be compared to thicknesses measured by SE.

The overall performance and correctness of the calibration of all kinds of traditional scanning probe microscopes can be assessed in a fully quantitative way by means of " crystallographic" processing of their two- dimensional (2D) images from samples with 2D periodic (and preferably highly symmetric) features. This is because crystallographic image processing results in two residual indices that quantify by how much the symmetry in a corresponding scanning probe microscopy image deviates from the symmetries of the possible plane groups of the periodic features of the sample. When a most probable plane symmetry group has been identified on the basis of crystallographic image processing, the symmetry in the scanning probe microscopy image can be "enforced" in order to obtain "clearer" images, effectively removing the less than ideal "influence" of the microscope on the imaging processes. This paper illustrated the crystallographic image processing procedure for scanning tunneling microscopy images that were recorded from a monolayer of a phthalocyanine on two different types of substrates.

Small Angle X‐ray Scattering (SAXS) is a possible candidate to complement and, in a longer term, to replace existing methods like CD‐SEM and OCD for measurements of CD profiles. Previously reported CD‐SAXS results were very promising; however as obtained using bulky sources as synchrotron, they are most often restricted to research rather than production control. We have designed a pilot set‐up (XCD™) around μ‐focus X‐tube, high‐luminosity focusing mirror‐monochromator and pixilated detector, having in mind that after further optimization of the components, the tool will have a suitable footprint and acceptable throughput. The system operates on MoKα (17.4 keV) beam shining through the wafer, from below. The measurement spot size is 100 μ. The angular resolution allows to measure structures with a pitch 100 nm and below. A software package was developed to simulate and process XCD spectra, taking into account all the components contributing to the instrumental function of the system. A special technique was developed for alignment. For the purpose of the feasibility study a special CD structure was prepared. It consists of Si trenches with 50 nm pitch. It was found that in a relatively short time, pitch and width can be extracted with a precision on the level 1% RSD. The depth of the trenches was measured using another independent X‐ray channel (fast XRR) operating on the CuKα line (8 keV) at the grazing angle, striking normally to the trenches direction.

Photoreflectance (PR) spectroscopy is employed as a non‐destructive and contactless technique for the characterization of silicon with SiO2 and HfO2 dielectric layers. The position of PR spectra reveals the critical point energy and the magnitude indicates the surface potential in silicon. By fitting PR spectra to a third‐derivative functional form, we find the critical point of silicon with a 1.0 nm SiO2 layer is 3.42 eV. The PR magnitude of samples with HfO2 dielectric layer decreases with layer thickness. This indicates the decreasing of surface potential with high‐κ layer thickness, possibly due to increased charge defects in the layer.

Beyond the 45 nm node, metal gate and high‐k will replace the poly‐ and silicon oxide‐based gate. Hence, new materials, aluminum oxide (AlOx), and lanthanum oxide (LaOx), are being developed for high‐k gate oxide and work function tuning applications. Device performance demands stringent thickness uniformity (1 to 2% 1σ) control on 300 mm wafers. However, most of the popular metrology tools are incapable of measuring these ultra‐thin (>20 A) films, either due to lack of sensitivity or due to a strong correlation of thickness with composition or other properties. Hence thickness and composition cannot be determined independently. To satisfy these metrology and characterization needs, wavelength dispersive X‐ray fluorescence (WD‐XRF) techniques are being developed. WD‐XRF has the advantages of long term stability, good sensitivity, and robust data analysis algorithms. Its applications for the thickness and composition metrology of RF PVD aluminum oxide and lanthanum oxide ultra‐thin films with 1 to 2% relat...

High‐k materials, such as HfO2, Al2O3, and many others, have been employed to replace the SiO2 insulator in the gate dielectric device in order to offer significant gate leakage reduction. In this study, the physical properties of hafnium dioxide (HfO2) thin films were analyzed and characterized in the cases of ‘as‐deposited’ and ‘post‐deposition annealing’ (PDA). Ultra‐thin hafnium dioxide films of thickness 2.5, 5 and 10 nm were deposited on Si (100) substrates using atomic layer deposition (ALD) at temperature of 300° C. After deposition, the films were annealed using furnace in Ar ambient for 10 minutes at 450° C, 550° C, 650° C and 750° C. The thickness, density, roughness and the crystalline evolution of the HfO2 films were investigated by Grazing Incidence X‐Ray Reflectometry (GIXRR) and Grazing Incidence X‐Ray Diffraction (GIXRD) for both as‐deposited and post‐annealing conditions. Transmission Electron Microscope (TEM) was used to provide image verification of the two‐layer model applied in XRR f...

Characterization of semiconductor thin films has long been determined by a number of traditional surface analysis techniques; Auger, ESCA/XPS, SEM‐EDS and SIMS to name only a few. Depth profiles, contamination in the thin film or quantitative stoichiometry are specific application examples that predicate the technique best suited for the analysis need. The evolution of photovoltaic (PV) thin film compositions with new chemistries and growing importance of atomic layer deposition (ALD) for semiconductor and nanoscale applications provide a sustaining need for thin film analyses along with an avenue for new analytical tools.In this paper we will discuss the applications of two non‐traditional material analysis techniques for the semiconductor and PV applications, glow discharge optical emission spectroscopy (RF GD‐OES) and laser ablation inductively coupled plasma mass spectrometry (LA ICP‐MS). Depth profiles are available via both techniques with the ability to analyze monolayers (single nm) as well as ana...

The downscaling of Metal‐Oxide‐Semiconductor Field‐Effect Transistor (MOSFET) devices leads to the implementation of a high dielectric constant oxide and a metal gate to improve the electrical performances. A detailed analysis of the chemical and structural properties of the gate stack is necessary to optimize the integration scheme. Here, the use of a synchrotron source is illustrated for non destructive analysis of the gate stack. Grazing Incidence X‐Ray Diffraction (GIXRD) is performed to investigate the crystalline structure of the layers. HfO2 is found to be in the monoclinic phase with no change after metal gate deposition. TiN is crystallized in the cubic phase with no variation after Poly‐Si deposition and spike anneal. HArd X‐ray PhotoElectron Spectroscopy (HAXPES) appears to be mandatory for a non destructive analysis of the buried high‐k / substrate interface. Experiments are scheduled at the ID32 beamline of the European Synchrotron Radiation Facility (ESRF) to highlight nitrogen diffusion fro...

Rutherford backscattering spectroscopy (RBS) has been an important analytical method for determination of the depth distribution of elemental concentrations in materials. The depth resolution of RBS is typically limited by the energy resolution of ion detectors. In this work we demonstrate the use of a compact magnetic spectrometer as the ion energy detector for high resolution RBS analysis. The magnetic spectrometer offers several advantages: (1) a high energy resolution ΔE/E∼1/2000; (2) a large bending power for MeV ions; and (3) a particular configuration allowing for true 180° RBS analysis. By combining this magnetic spectrometer with the grazing angle geometry, we have achieved a depth resolution better than 5 A for RBS analysis of concentration distributions in elemental (e.g., Ta) and compound (e.g. HfO 2 ) thin films using 2 MeV helium ions. These experimental results suggest that high‐resolution characterization of nanoscale thin films can be realized using MeV ions in conjunction with such magnetic spectrometers.

Gate‐all‐around (GAA) SiGe nanowire transistor structures have been studied using high angle annular dark field (HAADF) STEM tomography. Sample preparation has been optimized by isolating single devices in needle‐shaped specimens, using annular milling in the focused ion beam (FIB). Using this technique, images can be acquired over a tilt range up to +/−80°. Two dimensional simulations are used lo establish the optimum orientation for devices in this sample geometry. Tomograms are presented, and the impact of the “missing wedge” on the reconstruction is assessed, again with reference to two dimensional simulations.

NIST recently released a standard reference material (SRM) for the calibration of high resolution X‐ray diffraction (HRXRD) instruments. HRXRD is extensively used in the characterization of lattice distortion in thin single, epitaxial crystal layers on single‐crystal wafer substrates. Currently, there is a great need for improved accuracy and transferability for the measurement of strain fields in these epitaxial thin films. This implies an essential need for the calibration of HRXRD instruments to allow measurement intercomparison for both research and manufacturing communities. This first HRXRD SRM release provides certified measurements of diffraction features for a silicon reference substrate, Si (220) in transmission and Si (004) in reflection, allowing for calibration of either monochromator wavelength or goniometer angles. The SRM also provides information on the surface‐to‐crystal‐plane misalignment, which allows calibration of sample holders and sample alignment hardware. This calibration should reduce the uncertainties when comparing, for instance, reciprocal space maps. Here we present a detailed description of these measured values and provide methods for using these to calibrate HRXRD instrumentation. SRM 2000 provides the semiconductor and the larger nanoscience community with the first nanometer length‐scale reference standard with femtometer accuracy; the Si (220) transmission‐feature‐derived silicon lattice spacing, dSRM, has a value of 0.1920161 nm with an expanded uncertainty, U (dSRM), of 0.87 fm.

Electrical property measurements of nanoscale materials are important for characterization and understanding of materials and devices. Equally important is to measure these properties at various temperatures. These measurements are facilitated with cryogenic probe stations that provide a variable temperature environment over a wide range of temperatures. However, until this time a major inconvenience was caused by the thermal expansion of the probe tips and probe station as the temperature changed. To prevent the tip movement from damaging the sample, the normal procedure is to lift the probe tips as the temperature changes. This prevents the implementation of totally automated variable temperature measurements.

Interference microscopy satisfies many of the dimensional metrology requirements for semiconductor device interconnects manufacturing by providing 3D topography maps of patterned structures with sub‐nm vertical reproducibility. Analysis of topography maps and intensity images with pattern recognition software extends the metrology capability for CD, overlay and registration. This functionality is used in a flexible, multi‐purpose, inline process control tool for pre‐ and post‐metallization metrology on BEOL via and bump layers. Through Silicon Vias is another promising field of application, as demonstrated by the strong correlation of optical profiler results to cross‐section SEM reference metrology.

Light scattering has shown its powerful diagnostic capability to characterize optical quality surfaces. In this study, the theory of bidirectional reflectance distribution function (BRDF) was used to analyze the metallic nanoparticles’ sizes on wafer surfaces. The BRDF of a surface is defined as the angular distribution of radiance scattered by the surface normalized by the irradiance incident on the surface. A goniometric optical scatter instrument has been developed to perform the BRDF measurements on polarized light scattering on wafer surfaces for the diameter and distribution measurements of metallic nanoparticles. The designed optical scatter instrument is capable of distinguishing various types of optical scattering characteristics, which are corresponding to the diameters of the metallic nanoparticles, near surfaces by using the Mueller matrix calculation. The metallic nanoparticle diameter of measurement is 60 nm on 2 inch thin film wafers. These measurement results demonstrate that the polarization of light scattered by metallic particles can be used to determine the size of metallic nanoparticles on silicon wafers.

International audience; In this paper, the investigation of boron delta layers by atom probe tomography is used to demonstrate that a sub nanometer resolution (0.9 nm full-width at half-maximum, FWHM) can be achieved. This resolution is surprisingly lower than the intrinsic resolution observed in silicon (0.2 nm). Reconstruction artifacts are suggested. In this paper, the extent of reconstruction artifacts is evaluated using a model that reproduces the field evaporation of the sample and the image reconstruction. It is shown that reconstruction artifacts can only account for half of the resolution degradation, suggesting an actual physical depth of delta doped B layer of about 0.5 nm.

The Effective Medium Approximation, (EMA), theory validate the thin films optical metrology in most cases when considering surface roughness. A scaling condition exist between the light wavelengths as compared to thin films roughness. In earlier papers, D. Ramsey and later P. I. Rovira and R. W. Collins, S. F. Nee, had shown however that poly crystaline and textured films could induce light scattering, affecting deeply the SE results. Exhaustives studies in the literature, detail the Mueller matrices properties through optical entropy and depolarization. It has been applied in rather different fields. The mathematical basis, describing depolarizing systems, developped by S. R. Cloude, are an important issue. In the visible range optics, complementary applications exist for thin grating films, surface scatterometry and biological turbid media The optical entropy provides a very powerful analysis technique yielding important surface parameters such as depolarization and roughness, differentiating roughness ...

The advent of 3rd generation synchrotron sources coupled with high efficiency x‐ray focusing optics opened new nanocharacterization possibilities. This paper is an overview of synchrotron‐based techniques that may be of interest for nanotechnology researchers. Although not exhaustive, it includes a general background of synchrotron principle and main x‐ray interactions before addressing nanoimaging possibilities. Three‐dimensional (3D) hard x‐ray multimodal tomography is now doable that allows producing 3D morphological, chemical and crystalline images with a sub‐100 nm resolution. Although the resolution is still limited with respect to electron imaging, it presents attractive features like depth resolution and non‐destructive exam. Besides imaging, diffraction also allows strain determination within microstructures and is illustrated here on 100 nm copper lines. Surface analysis is illustrated through X‐ray Photoelectron Emission Microscopy (XPEEM).

One barrier to innovation confronting all phases of nanotechnology is the lack of accurate metrology for the characterization of nanomaterials. Ultra‐high resolution microscopy is a key technology needed to achieve this goal. But, current microscope technology is being pushed to its limits. The scanning and transmission electron microscopes have incrementally improved in performance and other scanned probe technologies such as atomic force microscopy, scanning tunneling microscopy and focused ion beam microscopes have all been applied to nanotechnology with various levels of success. A relatively new tool for nanotechnology is the scanning helium ion microscope (HIM). The HIM is a new complementary imaging and metrology technology for nanotechnology which may be able to push the current resolution barrier lower. But, successful imaging and metrology with this instrument entails new ion beam/specimen interaction physics which must be fully understood. As a new methodology, HIM is beginning to show promise and the abundance of potentially advantageous applications for nanotechnology have yet to be fully exploited. This presentation will discuss some of the progress made at NIST in understanding the science behind this new technique.

Backside Secondary Ion Mass Spectrometry (SIMS) profiling is a seemingly simple option to circumvent commonly observed depth resolution degradation in conventional front‐side SIMS. However, large practical barriers in backside sample preparation prohibit a wider and more routine use of backside SIMS. Here, we explore the use of XeF2 dry etching instead of wet etching for removal of the residual Si‐substrate. The former process is essentially isotropic with similar etch rates for the different crystallographic orientations and highly selective towards the dense thermal oxide (BOX). This eliminates the need for high‐precision polishing of individual samples, reducing the substrate removal to a few coarse and relatively rapid polishing steps only. Moreover, XeF2 etching can be performed in unattended fashion and simultaneously on multiple samples, greatly increasing volume and turn‐around time for backside sample preparation. Here we have explained the different practical aspects and demonstrated the feasibility of this novel approach for backside preparation for different front‐end (S/D contact silicide metal, high‐k metal gate) and back‐end (ECD‐Copper) of line applications. In conclusion, availability of a robust and reliable procedure for backside SIMS sample preparation with rapid turn‐around is highly beneficial for a more efficient analytical support of advanced IC process development.

The importance of adequate surface conditioning of silicon wafers for accurate and reproducible measurement of silicon electronic properties is discussed. The measurement results obtained with ac Surface Photo Voltage technique, following UV‐assisted oxidation and corona charge deposition are presented. The measurement requirements and mechanisms for the presented surface conditioning method are addressed. Improved measurement repeatability and uniformity across the wafer is demonstrated.

The use of ultra shallow distributions of dopant in silicon to realize source and drain extensions in CMOS devices requires the development of analytical techniques able to provide their quantitative characterization. Information like retained dopant fluence, depth distribution and damage evolution are of fundamental importance to tailor the ultra shallow p/n junctions. In this work a summary of a complementary approach developed within an European multi‐laboratories consortium (ANNA) is reported. Results obtained with several techniques on arsenic ultra low energy (0.5–5 keV) implants in Si are described. The employed techniques were secondary ion mass spectrometry, grazing incidence x‐ray fluorescence (with either conventional or synchrotron radiation excitation), neutron activation analysis, medium energy ion scattering, Z‐contrast annular dark field scanning transmission electron microscopy and spectroscopic ellipsometry. The cross comparisons of dose measurements, dopant distribution and damage build‐up behavior enabled a detailed characterization of the implanted samples and identified the overlap of information from each analytical techniques.

Dynamical X‐ray diffraction theory is extensively used to evaluate the structure of single crystal materials, where information on composition and strain can be extracted from high resolution rocking curves. Many critical materials and structures (lattice‐mismatched semiconductor heterostructures, or materials modified by ion implantation processing) may contain process‐induced structural defects and cannot be modeled by conventional perfect crystal dynamical theory approaches. Statistical dynamical diffraction theory (SDDT) incorporates both incoherent (kinematical and diffuse) and coherent (dynamical) scattering. Treatments of the SDDT theory are typically mathematically intensive while lacking instructions on how to actually implement the theory in practice. This paper discusses the implementation of the SDDT and modifications that allow for successful SDDT analyses of fully relaxed SiGe on Si.

X‐Ray Spectrometry (XRS) is a wide spread technique for revealing reliable information concerning the elemental composition and binding state in various materials. Reference‐free quantitation in x‐ray spectrometry is based on the knowledge of both the instrumental and fundamental atomic parameters. In different configurations, both matrix and trace constituents of a sample or layer thicknesses can be determined, even providing lateral or depth‐profiling elemental information. With respect to very flat samples, such as semiconductor wafers or structures, the photon energy and the angle of incidence of the exciting radiation determines the probing depth of XRS analysis. In total‐reflection geometry, i.e. having an angle of incidence smaller than the critical angle of total external reflection, only surface contamination and the surface‐near layer of a few nm contributes to the fluorescence spectra. Allowing the angle of incidence to be varied from close to zero up to about four times the critical angle of total external reflection, the probing depth ranges from a few up to several hundreds of nm. The methodological development of XRS at the Physikalisch‐Technische Bundesanstalt (PTB), Germany’s national metrology institute, is, among other issues, dedicated to high‐end investigations in the R&D of semiconductor samples requiring reference‐free methods, in particular for new materials where not enough appropriate reference materials are available. PTB can handle 200 mm and 300 mm silicon wafers, employing an EFEM module, as well as smaller semiconductor wafers in its XRS instrumentation. The use of undulator radiation in the PTB laboratory at BESSY is advantageous for off‐line contamination control on semiconductor surfaces as it provides very high photon fluxes for the efficient excitation of light elements. Optimizing the respective excitation conditions such as the angle of incidence and the incident photon energy, detection limits of light elements in the fg range can be achieved. Grazing incidence investigations demonstrated the capability for depth profiling of light elements in nanolayers. Reference‐free XRS has the potential to contribute to the thickness and composition analysis of nearly vertical sidewalls of semiconductor test structures. This technique is also able to contribute to the elemental depth‐profiling of ultra‐shallow junctions (USJ), i.e. near‐surface implantation profiles in wafers, as a complementary approach to other analytical techniques. At a given incident angle, XRS can be combined with x‐ray absorption spectroscopy (NEXAFS, XANES or EXAFS), revealing information on the depth profile of the chemical structure in a sample, e.g. about buried nanolayers or interfaces with varying chemical state.

Blanket HfO2 layers, deposited with 2 to 40 ALD cycles, were measured using VUV‐SR. The measured HfO2 thickness was compared to both XRR and process conditions. A linear correlation coefficient, R2, of 0.9977 to the number of ALD HfO2 cycles demonstrated sensitivity for the thickness range studied, 1.5 to 37 A, while the mean repeatability for thickness measurements (1−σ) was 0.05 A.

This work presents an as exhaustive as possible review of methods which can be applied for in‐line monitoring of implant processes. The dynamic of each technique was evaluated for several typical applications. This review shows that methods which are sensitive to electrically active dopants with the presence of a PN junction (post annealing metrology only) are quite well correlated and show a 1 to 1 dynamic. Indirect methods which can be used either pre or/and post anneal are more case to case metrologies with dynamics changing with the characteristics of implant.

In this paper a non‐damaging and non‐contaminating method for performing Capacitance‐Voltage (CV) and Current‐Voltage (IV) electrical characterization of advanced gate dielectrics and stack capacitor films is presented. The method uses a contacting Elastic Material Probe (EM‐Probe) that is made of a semiconductor compatible material and forms a gate contact diameter of about 30 to 50 microns. Key electrical parameters that are measured are, Capacitive Effective Thickness (CET), Equivalent Oxide Thickness (EOT), Interface Trap Density (Dit), delta VFB Hysteresis (ΔVFB), leakage current density (JLK), Field‐to‐breakdown (FBD), Charge‐to‐breakdown (QBD) and Stress Induced Leakage Current (SILC). Measurements can be made on either blanket or in scribe line test areas in patterned wafers.

This paper addresses advances in electron microscopy that were accomplished over the past years with the incorporation of new electron optical components such as aberration correctors, monochromators or high brightness guns. Many of these developments are currently pursued within the DoE’s TEAM project. As a result electron microscopy has reached 50 pm resolution. In this paper it is shown how the resolution improvement has helped to boost signal to noise ratios enabling a detection of single atoms across the Periodic Table of Elements. The described achievements allow for investigations of single point defects in nanoelectronic devices even if printed on single sheets of carbon atoms (graphene). Further it is now possible to access depth information from single projections with a precision that has reached interatomic distances.

Extreme Ultraviolet Lithography (EUVL) incorporates 13.5 nm light for patterning wafers and requires in‐situ wafer‐plane dosimetry that can be tailored to the requirements of an EUVL stepper’s environment. There are several types of detectors that are sensitive to EUV radiation including photodiodes, CCDs, and pyroelectrics to name a few. All of these require electrical connections and can be intrusive in a stepper’s projection optics box and will deteriorate with time causing changes to their calibration. The community has settled on using photoresist as a dosimeter in the wafer‐plane because it is a convenient non‐intrusive way to measure the dose in the wafer plane and it has very little overhead in the fab environment. However, recent experiments have found that the accepted values for the dose‐to‐clear for resists may not be accurate. In addition, dosimetry using a photoresist can be dependent on fab conditions and cause uncertainty due to varying process conditions.NIST has recently begun working on...

Scatterfield microscopy is a technique that combines the best attributes of scatterometry and high‐magnification imaging using a bright‐field microscope. In our work, we have traditionally moved an aperture in a conjugate back focal plane (CBFP) of the objective lens to control the angle of incidence. We have incorporated a new source into an existing microscope in order to scan the illumination wavelength, which has necessitated a new set of tool characterization requirements. We present experimental data and preliminary quantitative modeling results for metrology of sub‐wavelength features using this new method of illumination engineering.

We report the electrical characterization of vertically aligned nano‐objects by Scanning Spreading Resistance Microscopy (SSRM). In this paper, we show that this method is well suited to evaluate the individual electrical properties of carbon nanofibers and of n‐doped silicon nanowires. In the first example, carbon nanofibers exhibit a wide range of resistance which could be explained by the convolution of roughness and of surface oxidation of the TiN layer. An interpretation based on electrical contact resistance model is proposed here to explain this observation. In the second example, n‐doped Si NWs exhibit various range of resistance depending of the Phosphorus/Silicon ratio, which highlighted the control of the doping level.

Spectroscopic ellipsometry (SE) with VUV wavelength region has been used to characterize high‐k films grown on SiO2/Si. The high‐k stack thickness measurements by SE are compared to thickness measurements derived from angle resolved x‐ray photoemission spectroscopy. The optical properties of hafnium silicate change with silicate concentration, which is the mechanism for SE to measure this quantity. Other factors that affect high‐k optical properties such as N concentration and annealing are also investigated.

Grain size determination in advanced metallization structures requires a technique with resolution ∼2 nm, with a high signal‐to‐noise ratio and high orientation‐dependant contrast for unambiguous identification of grain boundaries. Ideally, such a technique would also be capable of high‐throughput and rapid time‐to‐knowledge. The Helium Ion Microscope (HIM) offers one possibility for achieving these aims in a single platform. This article compares the performance of the HIM with Focused Ion Beam, Scanning Electron and Transmission Electron Microscopes, in terms of achievable image resolution and contrast, using plan‐view and cross‐sectional imaging of electroplated samples. Although the HIM is capable of sub‐nanometer beam diameter, the low signal‐to‐noise ratio in the images necessitates signal averaging, which degrades the measured image resolution to 6–8 nm. Strategies for improving S/N are discussed in light of the trade‐off between beam current and probe size, accelerating voltage, and dwell time.

In this paper, we present the use of the micro‐thermal analyzer (TA Instruments model μTA‐2990) to detect lithographically‐defined surface and sub‐surface metal and dielectric features in silica and chalcogenide glass films. The imaging resolution of the technique was determined to be ±1 μm laterally for surface features, and up to 1μm for features located below the surface. We demonstrate that this instrument is also an effective technique for the detection of Au, Ag, and Cu nanoparticles within sol‐gel derived silica films. Lastly, we show that the micro‐thermal analyzer can also be used to measure thermal properties of bulk and film glassy materials, including thermal conductivity and probe penetration temperature.

Contact resistance is one of the major factors limiting the performance of future nanoelectronic devices. Although there has been significant progress in graphene based devices since 2004[1, 11, 13, 19, 20], there have been few studies of factors such as metal type, metal workfunction and number of layers in the graphene stack on metal/graphene contact resistance. In this work, contact resistance measurements of various metals (Cr, Ni, Pd, Pt) on Highly Oriented Pyrolytic Graphite (HOPG) and graphene (single layered and few layered) were performed. The total resistance is independent of distance indicating a contact resistance dominated system. The contact resistance is observed to be similar for a wide variety of metals although the metal workfunction varies from 4.3 eV to 5.6 eV. Similar measurements were performed for metal on single‐ and multi‐layer graphene. The electrical results are compared with XPS measurements of thin metal on HOPG. Issues regarding the characterization and interpretation of contact resistance for metal‐semimetal systems are discussed.

Precession electron diffraction (PED) in a transmission electron microscope (TEM) is discussed in order to illustrate its utility for structural fingerprinting of nanocrystals. While individual nanocrystals may be fingerprinted structurally from PED spot patterns, ensembles of nanocrystals may be fingerprinted from powder PED ring patterns.

Nanoscale metrology (thickness, defectivity) of carbon‐based devices is a substantial challenge due to device dimension scaling. Development of graphene‐based nanoelectronics required solutions for thickness and defect metrology owing to the difficulty of probing the atomic structure of individual graphene sheets. Distinguishing the number of graphene layers for a particular test structure as well as quantifying disorder for local defect characterization is essential to study graphene based devices. Raman spectroscopy has proved to be an appropriate approach in this regard for identifying and distinguishing the number graphene layers in thin (n

Variable angle spectroscopic ellipsometry (VASE) measurements from 30 μm (infrared) to 150 nm (vacuum ultraviolet) were used to measure the thickness, pore volume fraction, gradation in the refractive index and chemical bonding of porous low‐κ films. The VUV spectroscopic ellipsometry measurements were used to determine the pore volume fraction and gradation in the refractive index of the porous low‐κ films. Bruggeman’s effective medium approximation was used to calculate the total pore volume fraction. The IR spectroscopic ellipsometry measurements were used to characterize the chemical bonding of the porous low‐κ samples. Absorption coefficients in the IR wavelength were used to characterize the chemical bonding in the porous low‐κ films.

The response of a scanning Kelvin force microscope (SKFM) was measured with conventional micromachined silicon tips coated with Au and with advanced tips terminated with a carbon nanotube (CNT). A simple model of the SKFM predicts enhanced spatial resolution of the SKFM using a CNT terminated tip because it reduces the stray capacitance components due to the tip shank and the cantilever. SKFM measurements over abrupt boundaries between Au and silicon (with a thin silicon dioxide overlayer) show this predicted enhanced spatial resolution. The CNT‐terminated tip resolves the boundary to less than a micrometer, while the conventional Au‐coated tip smears the transition between the two materials over tens of micrometers.

The College of Nanoscale Science and Engineering of the University at Albany in collaboration with International SEMATECH is investigating the use of Scanning Acoustic Microscope (SAM) for analyzing 3D Interconnects. SAM is a non‐destructive metrology technique which utilizes high frequency ultrasound to generate a microscopic image of the internal parts of a specimen. The goal of this project is to develop microscopic techniques for evaluating Through‐Silicon Vias (TSVs) for 3D‐Interconnects. Preliminary data shows voids and other defects in the interface between bonded wafers as shown in Figure 1. Our SAM laboratory system operates at 230 MHz and has a spatial resolution of 5–10 μm and focal length of 5.9 mm on a silicon wafer. The spatial resolution and sampling depth depend on the ultrasonic frequency, sound velocity, focal length and diameter of piezoelectric crystal. Typically, the silicon wafers have a thickness of 775 μm before they are bonded. Our initial work is focused on blanket wafers in order to develop the bonding process. The next step is to bond wafers with test die where the patterning obscures the interface. This paper will discuss the limitations of SAM and compare it to infrared microscopy which is another important imaging capability for 3D Interconnect. We also discuss the current status of research into more advanced acoustic microscopy methods and how this might impact 3D Interconnect imaging.

Spectroscopic ellipsometry (SE) and resistivity measurements were used to characterize Nickel‐metal films used for self‐aligned silicidation process. Variable angle spectroscopic ellipsometer (VASE) in the VUV range of wavelengths was used to measure the thickness and optical properties of Nickel films. The thickness‐dependent optical properties of thin‐metal films are shown to be correlated to the change in electron relaxation time and resistivity. The change in electron relaxation time and resistivity can be traced to the change in grain boundary reflection coefficient and grain size. X‐ray photoelectron spectroscopy (XPS) data aided with sputtering is used to show the evidence of the various stack layers that would be used in the VASE modeling. X‐ray reflectivity (XRR) and Rutherford backscattered spectroscopy (RBS) measurements on thin‐metal films were performed to complement the thickness measurements made with SE.

The continuous race to reduce the dimensions of IC components has lead to the introduction of Nitrogen in the thin gate oxide layer in order to increase the dielectric constant and to improve the gate dielectric properties. It is mandatory to apply in‐line monitoring to control the amount of Nitrogen to ensure that electrical behavior is correct over time. Historically, this monitoring was performed by measuring the delay to reoxidation (D2R) with an ellipsometer. But, this method is not suitable in production as it is depending on both initial oxidation and reoxidation reproducibility, which implies implementing dedicated Statistical Process Control (SPC) monitoring at these two specific processing steps. We are here presenting an alternative method to D2R for 90 nm Technology gate oxide grown by Rapid Thermal Process (RTP). Applying a non‐contact Metrology technique, which couples Kelvin probe surface voltage measurement with surface Corona deposition, directly after the nitridation step, the interface ...

The impact of organic contamination on wafer surfaces on the functionality of nanostructures and advanced microelectronics becomes crucial as the continuously shrinking feature sizes become similar to the dimensions of molecules and clusters of molecules. Especially, manufacturing of highly integrated circuits requires clean surfaces as processes might cause defects involving for example carbon and sulfur. The approach to study organic contamination on wafer samples using different analytical tools enables the detection of the whole range of organic compounds including non‐volatile and volatile ones. For the studies the methods used were synchrotron radiation based Near Edge X‐ray Absorption Fine Structure (NEXAFS) in the soft X‐Ray range at the absorption edges of light elements (e.g. C, N, O, F) combined with reference‐free Total‐reflection X‐Ray Fluorescence (TXRF) analysis, Thermal Desorption Gas Chromatography Mass Spectrometry (TD‐GCMS), and Time of Flight Secondary Ion Mass Spectrometry (TOF‐SIMS). TOF‐SIMS analysis of the surfaces of wafers from the lithography process after ashing showed sulfur compounds related to resist residues not identified by TD‐GCMS. The source of the sulfur is assumed to be a photo acid generator of the resist. It was proven by TD‐GCMS and TXRF‐NEXAFS that final clean and packaging were the process steps during which detectable organic contamination was transferred to the wafer surface during wafer manufacturing. Multi‐criteria evaluation of the TXRF NEXAFS spectra was used to compare the results with TD‐GCMS. The TXRF‐NEXAFS results are in good agreement with the TD‐GCMS results. The advantage of TXRF‐NEXAFS and TOF‐SIMS are the sensitivity for organic contaminants that are not detectable by TD‐GCMS, due to their high boiling point and low vapor pressures.

Implementation of Cu interconnects into Silicon Integrated Circuits (IC’s) has been instrumental in the continuing improvement of IC device performance. Copper as a well known Gate Oxide Integrity (GOI) killer [1, 2] requires extensive protocols to minimize the possibility of cross contamination. Despite such protocols the risk for cross contamination exists, and consequently there is the need for in‐line Cu cross‐contamination detection metrology. Preferably the metrology will be non‐destructive, fast, and capable of mapping on product wafers. Up to now the most common approaches for monitoring Cu contamination in IC fabrication lines either measure Cu in the bulk Si, which is not applicable to Cu cross‐contamination monitoring because Back‐End‐of‐the‐Line thermal budgets restrict the ability to diffuse the surface Cu into the bulk Si; or the techniques are not optimal for in‐line monitoring due to their destructive, time‐consuming, or costly nature. In this work we demonstrate for the first time the application of the ac‐Surface Photo Voltage (ac‐SPV) surface lifetime approach [3] to in‐line, full wafer coverage mapping of low level (

X‐ray computed tomography (XCT) offers powerful non‐destructive three dimensional imaging capability widely used in diverse fields, including medical diagnosis, biomedical and material research, geology, petrology, and archeology. XCT with micrometer resolution is being rapidly adopted for semiconductor packaging process development and failure analysis by creating virtual cross sections without the time consuming destructive cross sectioning processes. Thanks to rapid advancements in x‐ray imaging technology, XCT with 30 nm and 50 nm resolution (nanoXCT) has been developed using synchrotron and laboratory x‐ray sources, respectively. The nanoXCT can image internal structures of semiconductor IC devices that are fabricated using the latest IC manufacturing technology. This new capability is very valuable to the characterization of semiconductor interconnects for process development and failure analysis. We will present the design, specification, and operation of the nanoXCT. 2D and 3D tomographic reconstruction images from IC devices will be presented to show the tomography microscope’s outstanding performances.

Development of a rational synthetic method of flexible nanomaterials may enable exciting avenues in both fundamental research and novel device applications. In this paper, flexible boron nanowires have been successfully synthesized on both Si (111) and scanning tunneling microscope (STM) tungsten (W) tips via thermoreduction of boron‐oxygen compounds with active metal (magnesium). These as‐prepared nanowires, which are structurally uniform and single crystalline, represent good semiconductor at high temperature. Electrical conductivity of these intrinsic nanowires can be improved two orders by introducing doping atoms. Tensile stress measurements demonstrate excellent mechanical property of as‐synthesized boron nanowires as well as resistance to mechanical fracture even under a strain of 3%. Importantly, simultaneous electrical measurement reveals that the corresponding electrical conductance is very robust and remains constant under mechanical strain. Our results can be briefly explained by Mott’s variable range hopping (VRH) model. A stable field emission current was also observed from a single boron nanowire. Boron nanostructures with excellent controllability, remarkable mechanical flexibility and field emission characteristics represent promising candidates for flexible nanoelectronic circuits as well as electron emission nanodevices.