FRONTIERS OF CHARACTERIZATION AND METROLOGY FOR NANOELECTRONICS: 2009
1173(2009); http://dx.doi.org/10.1063/1.3251256View Description Hide Description
New switches are being designed based on carrier spin, excitons, and other properties. Graphene is considered a strong candidate for many of these applications. New phenomena abound at nanoscale dimensions, and graphene is no exception. Quantum confinement impacts materials properties and measurement itself. Berry Phase corrections to carrier transport measurements are widely recognized. New materials such as graphene are difficult to find, manipulate, and measure. One key question is the number of graphene layers in a sample and the stacking of multilayer samples. Multiple characterization methods are necessary including transmission electron microscopy (TEM), Low Energy Electron Microscopy (LEEM), nano‐Raman, and several scanned probe methods. Multislice simulations are a useful guide in determining TEM capability and imaging conditions. Initial simulation work points to the ability to distinguish stacking patterns. Recent work indicates that LEEM can determine the number of layers and the morphology of a graphene sample. Raman provides an excellent means of determining the number of layers in a stack of graphene. Single electron transistors have mapped electron‐hole puddles across a sample area. Quantum confinement and Berry Phase corrections are two examples of quantum phenomena that alter the properties of nano‐scale structures. Optical and electrical properties must be understood before they are measured. This paper will cover the research and development of metrology for CMOS Extension and Beyond CMOS using graphene as an example.
1173(2009); http://dx.doi.org/10.1063/1.3251207View Description Hide Description
Depending on the level of the technological developments, the characterization techniques are mature to support them or still require protocol definition and relevance demonstration for the issues addressed. For Beyond CMOS and Extreme CMOS devices, the integration of nano‐objects like nanowires and carbon nanotubes, brings about analysis requirements that are at the frontier of the state‐of‐the‐art characterization techniques. The specific limitations of the use of the existing physical and chemical characterization techniques for integrated nanomaterials are highlighted. In the case of Scanning Probe Microscopy, in‐situ localization and positioning are specifically challenging and data analysis is mainly statistical. It is also shown how specific sample preparation may serve the extraction of the required 3D information in particular for Electron Microscopy. The measurement developments related to NEMS technologies guided by the need for dynamic characterization of these components are covered too.
1173(2009); http://dx.doi.org/10.1063/1.3251227View Description Hide Description
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.
1173(2009); http://dx.doi.org/10.1063/1.3251239View Description Hide Description
Grazing Incidence X‐Ray Fluorescence (GIXRF) analysis in the soft X‐ray range provides excellent conditions for exciting B‐K and shells. The X‐ray Standing Wave field (XSW) associated with GIXRF on flat samples is used as a tunable sensor to gain information about the implantation profile in the nm range due to the in‐depth changes of the XSW intensity dependent on the angle between the sample surface and the primary beam. This technique is very sensitive to near surface layers. It is therefore well suited for the study of ultra shallow dopant distributions. Arsenic implanted (100) Si wafers with nominal fluence between and and implantation energies between 0.5 keV and 5.0 keV and Boron implanted (100) Si wafers with nominal fluence of and and implantation energies between 0.2 keV and 3.0 keV have been used to compare SIMS analysis with synchrotron radiation induced GIXRF analysis in the soft X‐ray range. The measurements have been carried out at the laboratory of the Physikalisch‐Technische Bundesanstalt at the electron storage ring BESSY II using monochromatized undulator radiation of well‐known radiant power and spectral purity. Here the use of an absolutely calibrated energy‐dispersive detector for the registration of the B‐Kα and As‐Lα fluorescence radiation allows for the absolute determination of the total retained dose. An estimate of the concentration profile has been obtained by fitting the X‐ray fluorescence angular scans with profiles derived by simulation of the implantation process. A good match among the total retained dose measured with the different techniques has been observed.
1173(2009); http://dx.doi.org/10.1063/1.3251249View Description Hide Description
Beyond the 45 nm node, metal gate and high‐k will replace the poly‐ and silicon oxide‐based gate. Hence, new materials, aluminum oxide and lanthanum oxide 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 Å) 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% relative 1σ data precision has been demonstrated.
1173(2009); http://dx.doi.org/10.1063/1.3251257View Description Hide Description
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. 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 from the metal gate towards the pedestal interfacial oxide.
Multi‐technique characterization of arsenic ultra shallow junctions in silicon within the ANNA consortium1173(2009); http://dx.doi.org/10.1063/1.3251258View Description Hide Description
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.
1173(2009); http://dx.doi.org/10.1063/1.3251259View Description Hide Description
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, has a value of 0.1920161 nm with an expanded uncertainty, of 0.87 fm.
1173(2009); http://dx.doi.org/10.1063/1.3251260View Description Hide Description
As the MOSFET ‐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. 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 layer and annealing of the 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.
1173(2009); http://dx.doi.org/10.1063/1.3251261View Description Hide Description
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 analysis in the bulk (μm thickness). Depth resolution capabilities allow analysis without surface equilibrium issues seen with other techniques. In addition, the charging effect that can cause issues with electron and ion beam techniques is avoided with RF GD‐OES and LA ICP‐MS, and thus analysis of both conductive and non‐conductive materials is very straight‐forward.
Contaminant analysis in thin films is very straight‐forward and elements across the periodic table are analyzed in a simultaneous mode with both techniques. Detection limits to part‐per‐billion levels can be achieved and quantitation at low concentrations up to 99% achieved with LA ICP‐MS. Lastly, t will be discussed that for some thin film applications, LA ICP‐MS and RF GD‐OES provide advantages over more traditional techniques, and these aspects as well as complementary features will be discussed.
1173(2009); http://dx.doi.org/10.1063/1.3251262View Description Hide Description
In conventional 200 mm wafer processing, backside defects are not considered to be of much concern because they are obscured by wafer backside topography. However, in current 300 mm wafer processing where both sides of a wafer are polished, backside defects require more consideration. In the beginning, backside defect inspection examined particle contamination because particle contamination adversely influences the depth of field in lithography. Recently, metal contamination is of concern because backside metal contamination causes cross‐contamination in a process line, and backside metals easily transfer to the front surface. As the industry strives to yield more devices from the area around the wafer edge, edge exclusion requirements have also become more important. The current International Technology Roadmap for Semiconductors  requires a 2 mm edge exclusion. Therefore, metal contamination must be controlled to less than 2 mm from the edge because metal contamination easily diffuses in silicon wafers. To meet these current semiconductor processing requirements, newly developed zero edge exclusion TXRF (ZEE‐TXRF) and backside measurement TXRF (BAC‐TXRF) are effective metrology methods.
1173(2009); http://dx.doi.org/10.1063/1.3251263View Description Hide Description
Blanket layers, deposited with 2 to 40 ALD cycles, were measured using VUV‐SR. The measured thickness was compared to both XRR and process conditions. A linear correlation coefficient, of 0.9977 to the number of ALD cycles demonstrated sensitivity for the thickness range studied, 1.5 to 37 Å, while the mean repeatability for thickness measurements was 0.05 Å.
Application Of The SPV‐based Surface Lifetime Technique To In‐Line Monitoring Of Surface Cu Contamination1173(2009); http://dx.doi.org/10.1063/1.3251264View Description Hide Description
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  to in‐line, full wafer coverage mapping of low level (<1E9 cm‐2) surface Cu contamination. The low level sensitivity is achieved through integration of a novel preferential surface Cu activation procedure into a production ready metrology system. Furthermore, because the metrology is non‐contact (utilizing edge‐grip handling) and non‐destructive, it is directly applicable to measurement of production wafers. In‐line fab data acquired using this metrology is presented and compared to data from Inductively Coupled Plasma Mass Spectroscopy (ICP‐MS).
1173(2009); http://dx.doi.org/10.1063/1.3251265View Description Hide Description
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 Å for RBS analysis of concentration distributions in elemental (e.g., Ta) and compound (e.g. ) 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.
1173(2009); http://dx.doi.org/10.1063/1.3251266View Description Hide Description
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.
1173(2009); http://dx.doi.org/10.1063/1.3251267View Description Hide Description
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 delta Hysteresis leakage current density Field‐to‐breakdown Charge‐to‐breakdown and Stress Induced Leakage Current (SILC). Measurements can be made on either blanket or in scribe line test areas in patterned wafers.
Towards Routine Backside SIMS Sample Preparation for Efficient Support of Advanced IC Process Development1173(2009); http://dx.doi.org/10.1063/1.3251268View Description Hide Description
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 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, 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.
1173(2009); http://dx.doi.org/10.1063/1.3251269View Description Hide Description
We have studied spatial variations of the electronic structure of p‐n doping silicon patterns using energy filtered X‐ray Photoelectron Emission Microscope (XPEEM). Simultaneous lateral and spectroscopic information can be obtained with this direct, non‐destructive method which allows high lateral and energy resolutions. The use of synchrotron radiation allows simultaneous measurement of the work function and acquisition of spectroscopic image series at the Si 2p core‐level and valence band on highly P and N doped silicon patterns. This paper highlights the capability of XPEEM to study the variations in electronic band alignments at the native oxide/substrate interface as a function of the substrate doping level.
1173(2009); http://dx.doi.org/10.1063/1.3251202View Description Hide Description
Spectroscopic ellipsometry (SE) with VUV wavelength region has been used to characterize high‐k films grown on 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.