Tiefenprofilanalysen und TEM-Querschnitte von Tantalsilicid-Polysilicium-Doppelschichten

Zusammenfassung Die Augerelektronen-Spektrometrie (AES), die Sekundärionen-Massenspektrometrie (SIMS) und die Abbildung von dünnen Querschnitten im Transmissionselektronenmikroskop (TEM) ergänzen sich in wertvoller Weise: TEM-Querschnitte geben den Aufbau und die Morphologie der Schichten mit sehr hoher Ortsauflösung (<1 nm) sowohl in lateraler als auch vertikaler Richtung wieder, AES und SIMS bieten die zugehörige Elementanalyse von Hauptbestandteilen, Verunreinigungen und Dotierstoffen über die Tiefe. Die Nützlichkeit der Kombination dieser Methoden wird an Tantalsilicid-Polysilicium-Doppelschichten aus der modernen MOS-Technologie veranschaulicht.

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Depth profiling analyses and TEM cross sections of tantalum silicide-polysilicon double layers

Summary Auger Electron Spectroscopy (AES), Secondary Ion Mass Spectrometry (SIMS), and cross-sectional Transmission Electron Microscopy (TEM) favourably complement one another in the analysis of thin film problems: Cross sectional TEM images reveal the structure and the morphology of thin films with very high spatial resolution (< 1 nm) in lateral as well as in vertical direction, whereas AES and SIMS provide the corresponding elemental analyses of major components, impurities, and doping elements as a function of film depth. The combined application of these methods is shown for the case of tantalum silicidepolysilic on double layers used in modern MOS devices.

     

Application of SIMS in semiconductor research

Summary Nowadays SIMS is a well-established analytical technique in semiconductor research. Materials research and process development are the main fields of application in silicon technology, whereas for III–V compound semiconductors much attention has been paid to assessment of multilayer structures grown by advanced growth methods. Recent applications of SIMS in these fields are the subject of the present paper. Emphasis will be placed upon optimizing the SIMS results with respect to accuracy and depth resolution.

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Anwendungen von SIMS in der Halbleiterforschung

     

Quantitative ultratrace distribution analysis of tantalum wires with SIMS

Summary The potential of SIMS for multielement ultratrace bulk analysis in refractory metals has already been shown in previous publications [1, 2]. In this paper it will be demonstrated, that the high sensitivity of SIMS can be used advantageously for high resolution distribution analysis. Due to the high useful yield (0.5 to 10^–5) it is possible to perform distribution analysis in the ng/g range with a sample consumption of about 1 pg per data point. A good lateral resolution of about 1 m and the variability of the sputtering rate over 3 orders of magnitude allow an optimization of the measurement parameters with respect to the sample geometry. This is of special importance in our work, because small lateral dimensions, high total sputtering depth (300 m) and crooked surfaces have to be considered. In this paper also the technical significance of sensitive high resolution distribution analysis of tantalum wires, which are used for microelectronic applications, will be discussed.

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Quantitative Ultraspuren-Verteilungsanalyse von Tantaldrähten mit Hilfe von SIMS

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Dedicated to Prof. Dr. G. Tölg on the occasion of his 60th birthday     

A combination of atomic force microscopy and secondary ion mass spectrometry for investigation of AlxGa1?xAs/GaAs superlattices

Summary Atomic Force Microscopy (AFM) has been used to characterize the topography of crater bottoms obtained during Secondary Ion Mass Spectrometry (SIMS) investigations of an Al_0.35Ga_0.65As/GaAs multilayer system. A linear relation between the roughness of the bottoms, which leads to a drop in the dynamic range of the SIMS-signal and in the depth resolution, and the sputter depth of SIMS has been found. The topography found by AFM also supports a mechanism for the ripple formation proposed recently by W. H. Gries. AFM imaging of cleaved cross sections through this multilayer system allowed to determine evenness and thickness of individual layers, which opens up the possibility to improve the depth scale for sputter techniques like SIMS.     

Eignung von Tiefenprofilanalysen zur Charakterisierung von Oxidschichten an Hochtemperaturlegierungen

Summary The characterization of oxide scales by their composition and structure is necessary in order to predict their protective behaviour for the high temperature alloys in various corrosive media. For this purpose information obtained by classical methods, such as metallography, X-ray diffraction and microprobe analysis can be supplemented by depth profiles determined by various spectroscopical methods.In this paper, HASTELLOY X und INCONEL 617 were oxidized for relatively short times in two different atmospheres. Depth profiles were determined by GDOS (Glow Discharge Optical Spectroscopy), SNMS (Secondary Neutral Mass Spectrometry) and SIMS (Secondary Ion Mass Spectrometry).The measured profiles were compared with the results of non-destructive X-ray diffraction analysis to characterize the scales and the oxide-metal interface.     

SIMS-Analyse von optischen Fasern

Summary Secondary Ion Mass Spectrometry (SIMS) has found until now virtually no application for characterizing optical fibers. Certainly, one of the reasons was the lack of commercial instruments which combine a lateral resolution in the sub-m range with electron flooding for reducing electrostatic charging. Possible methods to determine the concentration profiles of doping elements in optical fibers are discussed and linescans on bevelled polished cross sections are shown to yield satisfactory radial resolution. First experimental results obtained with a previous-generation ion microprobe indicate the expected capability of SIMS to characterize optical fibers.     

SIMS depth profiling of vertical p-channel Si-MOS transistor structures

SIMS depth profiling during O₂ ⁺ bombardment has been performed to analyse epitaxially grown Si p-n-p layers, which define the p-channel region in vertical Si-p MOS transistors, as well as to establish “on-chip” depth profiling of the functional vertical device. The SIMS detection limit of ³¹P in Si, phosphorus used as n-type dopant in the transistor, has been optimised as a function of the residual gas pressure in the SIMS analysis chamber and of the sputter erosion rate. We demonstrate that good vacuum during SIMS analysis combined with high erosion rates allows the simultaneous quantitative SIMS depth profiling of n- and p-type dopant concentrations in the vertical transistor. Small area “on-chip” SIMS depth profiling through the layered structure of Al-contact/TiSi₂/Si(p-n-p)/Si-substrate has been performed. Factors influencing the depth resolution during “on-chip” analysis of the transistor are discussed especially in terms of sputtering induced ripple formation at the erosion crater bottom, which has been imaged with atomic force microscopy. Received: 15 August 1996 / Revised: 17 January 1997 / Accepted: 21 January 1997     

Development of B‐doped Si multiple delta‐layer reference materials for SIMS profiling

B‐doped Si multiple delta‐layers (MDL) were developed as certified reference materials (CRM) for secondary ion mass spectrometry (SIMS) depth profiling analysis. Two CRMs with different delta‐layer spacing were grown by ion beam sputter deposition (IBSD). The nominal spacing of the MDL for shallow junction analysis is 10 nm and that for high energy SIMS is 50 nm. The total thickness of the film was certified by high resolution transmission electron microscopy (HR‐TEM). The B‐doped Si MDLs can be used to evaluate SIMS depth resolution and to calibrate the depth scale. A consistency check of the calibration of stylus profilometers for measurement of sputter depth is another possible application. The crater depths measured by a stylus profilometer showed a good linear relationship with the thickness measured from SIMS profiling using the calibrated film thickness for depth scale calibration. The sputtering rate of the amorphous Si thin film grown by sputter deposition was found to be the same as that of the crystalline Si substrate, which means that the sputtering rate measured with these CRMs can be applied to a real analysis of crystalline Si. Copyright © 2005 John Wiley & Sons, Ltd.     

Progress in materials analysis with SIMS: Quantitative surface and interface characterization

Summary The potential and limitations of SIMS for quantitative surface and interface characterization of technical materials are described. Quantification procedures, figures of merit and analytical strategies are discussed for surface characterization of single cristals (dopant elements in Si), homogeneous metallic thin films (multielement trace analysis), heterogeneous glass layer structures (corrosion behaviour), polycristalline metals with precipitations (C, O, Al, Si in steel) and interface analysis by depth profiling (Cr distribution in Si₃N₄/GaAs) as well as step scanning (segregation studies of P in W-NiFe).

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Fortschritte der Werkstoffanalyse mit SIMS: Quantitative Grenzflächencharakterisierung

Zusammenfassung Die Möglichkeiten und Grenzen von SIMS für die quantitative Grenzflächencharakterisierung in Werkstoffen wurden beschrieben. Quantifizierungsverfahren, analytische Gütekennziffern und Strategien wurden an folgenden Beispielen diskutiert: Oberflächenanalyse von Einkristallen (Dotierungselemente in Silizium), homogenen metallischen Dünnfilmstrukturen (Multielement-Spurenanalyse) und polykristallinen Materialien mit Ausscheidungen (C, O, Al, Si in Stahl); Grenzflächenanalyse durch Aufnahme von Tiefenprofilen (Verteilung von Cr zwischen Si₃N₄ und GaAs) und Linienprofilen (Segregation von P in W-NiFe).

     

Quantitative profiling of SiGe/Si superlattices by time-of-flight secondary ion mass spectrometry: the advantages of the extended Full Spectrum protocol

The abundance of work on SiGe-based devices demonstrates the importance of the compositional characterization of such materials. However, Secondary Ion Mass Spectrometry (SIMS) characterization of SiGe layers often suffers from matrix effects due to the non-linear variation of ionization yields with Ge content. Several solutions have been proposed in order to overcome this problem, each having its own limitations such as a restricted germanium concentration range, or a weak sensitivity to dopants or impurities. Here, we studied the improvements brought by an alternative protocol: the extended Full Spectrum protocol, which states proportionality between the composition of the secondary ion beam and that of the actual material. Previous studies on this protocol showed that it was extremely precise and reproducible for Ge quantification in a permanent regime, because of minimized matrix effects. In this study we thus investigated its accuracy for the simultaneous quantitative depth profiling of both matrix elements (Si, Ge) and impurities (B, C or P) in strained SiGe/Si superlattices by comparing results with those from more classic protocols. The profiles provided by the extended Full Spectrum protocol were found to be accurate, and to exhibit better properties than classic protocols in terms of signal/noise ratio and signal stability, along with a slight enhancement in depth resolution.     

Depth profiling in secondary ion mass spectrometry for ultra‐thin layer with nanometer order thickness by mesa‐structure fabrication

We attempted to make an accurate depth profiling in secondary ion mass spectrometry (SIMS) including backside SIMS for ultra‐thin nanometer order layer. The depth profiles for HfO₂ layers that were 3 and 5 nm thick in a‐Si/HfO₂/Si were measured using quadrupole and magnetic sector type SIMS instruments. The depth profiling for an ultra‐thin layer with a high depth resolution strongly depends on how the crater‐edge and knock‐on effects can be properly reduced. Therefore, it is important to control the analyzing conditions, such as the primary ion energy, the beam focusing size, the incidence angle, the rastered area, and detected area to reduce these effects. The crater‐edge effect was significantly reduced by fabricating the sample into a mesa‐shaped structure using a photolithography technique. The knock‐on effect will be serious when the depth of the layer of interest from the surface is located within the depth of the ion mixing region due to the penetration of the primary ions. Finally, we were able to separately assign the origin of the distortion to the crater‐edge effect and knock‐on effect. Copyright © 2012 John Wiley & Sons, Ltd.     

Multielement ultratrace analysis in tungsten using secondary ion mass spectrometry

Summary The ever increasing demands on properties of materials creates a trend also towards ultrapure products. Characterization of these materials is only possible with modern, highly sophisticated analytical techniques such as activation analysis and mass spectrometry, particularly SSMS, SIMS and GDMS [1].Analytical strategies were developed for the determination of about 40 elements in a tungsten matrix with high-performance SIMS. Difficulties like the elimination of interferences had to be overcome. Extrapolated detection limits were established in the range of pg/g (alkali metals, halides) to ng/g (e. g., Ta, Th).Depth profiling and ion imaging gave additional information about the lateral and the depth distribution of the elements.

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Multielementepurenanalyse in Wolfram mittels SIMS

     

Atom probe mass spectrometry

Round-robin characterization is reported on the sputter depth profiling of CrN/AlN multilayer thin-film coatings on nickel alloy by secondary ion mass spectrometry (SIMS) and glow-discharge optical emission spectrometry (GD-OES). It is demonstrated that a CAMECA SIMS 4550 Depth Profiler operated with 3 keV O₂⁺ primary ions provides the best depth resolution and sensitivity. The key factor is sample rotation, which suppresses the negative influence of the surface topography (initial and ion-induced) on the depth profile characteristics.     

Multilayer thin-film coatings based on chromium nitride and aluminum nitride: Comparative depth profiling by secondary ion mass spectrometry and glow-discharge optical emission spectrometry

Round-robin characterization is reported on the sputter depth profiling of CrN/AlN multilayer thin-film coatings on nickel alloy by secondary ion mass spectrometry (SIMS) and glow-discharge optical emission spectrometry (GD-OES). It is demonstrated that a CAMECA SIMS 4550 Depth Profiler operated with 3 keV O ₂ ⁺ primary ions provides the best depth resolution and sensitivity. The key factor is sample rotation, which suppresses the negative influence of the surface topography (initial and ion-induced) on the depth profile characteristics.     

Correlated Secondary Ion Mass Spectrometry-Laser Scanning Confocal Microscopy Imaging for Single Cell-Principles and Applications

Secondary ion mass spectrometry (SIMS) as a powerful surface analysis technique has been widely applied in semiconductor industry and geology research. Recently, with the development of instrumental technology, SIMS is attracting more and more attention in life sciences. SIMS can provide surface MS spectra, 2D/3D chemical images and depth profiling of substances simultaneously. The minimal lateral resolution of 2D SIMS imaging is 80–100 nm, and the longitudinal resolution of 3D SIMS imaging is about 1–5 nm. However, owing to lack of specific ions to render the structures of organelles, SIMS imaging for single cells still have great challenges. Optical microscopy, in particular laser scanning confocal microscopy (LSCM), has been emerged to be an indispensable technique for single cell imaging and can obtain high spatial 2D/3D imaging to visualize the structures of organelles. Thus, the combinational use of SIMS and LSCM, which takes advantages of SIMS for molecular imaging and LSCM for morphological imaging, has greatly extended the application of SIMS imaging and ensured its accuracy at single cells level, providing novel insights into better understanding of the biological events inside cells. In this review, we focus on the development and application of SIMS imaging and the correlated SIMS and LSCM imaging in the research of cell biology and drug discovery. We anticipate that the combinational use of SIMS and LSCM imaging has promising future in biomedicine and life sciences.     

Depth profile analysis of thin film solar cells using SNMS and SIMS

SNMS (sputtered neutrals mass spectrometry) and SIMS (secondary ion mass spectrometry) are used for the depth profile analysis of thin film solar cells based on amorphous silicon. In order to enhance depth resolution, model systems are analyzed only representing parts of the layered system. Results concerning the TCO (transparent conducting oxide)/p interface and the n/i interface are presented. To minimize matrix effects, SNMS is used when the sample consists of layers with different matrices. Examples are the TCO/p interface (where the transition lengths of the depth profiles are found to be sharper when ZnO is used as TCO compared to SnO₂) and SnO₂/ZnO interfaces in coated TCO layers (where a Sn contamination inside the ZnO layer is found depending on the plasma pressure during the ZnO deposition). SIMS is used when the limits of detection reached by SNMS are not sufficient. Examples are H depth profiles in ZnO layers or P depth profiles near the n/i-interface.     

A new approach to express ToF SIMS depth profiling

We propose a new approach to express SIMS depth profiling on a TOF.SIMS‐5 time‐of‐flight mass spectrometer. The approach is based on the instrument capability to independently perform raster scans of sputter and probe ion beams. The probed area can be much smaller than the diameter of a sputter ion beam, like in the AES depth profiling method. This circumstance alleviates limitations on the sputter beam–raster size relation, which are critical in other types of SIMS, and enables analysis on a curved‐bottomed sputter crater. By considerably reducing the raster size, it is possible to increase the depth profiling speed by an order of magnitude without radically degrading the depth resolution. A technique is proposed for successive improvement of depth resolution through profile recovery with account for the developing curvature of the sputtered crater bottom in the probed area. Experimental study of the crater bottom form resulted in implementing a method to include contribution of the instrumental artifacts in a nonstationary depth resolution function within the Hofmann's mixing–roughness–information depth model. The real‐structure experiment has shown that the analysis technique combining reduction of a raster size with a successive nonstationary recovery ensures high speed of profiling at ~100 µm/h while maintaining the depth resolution of about 30 nm at a 5 µm depth. Copyright © 2015 John Wiley & Sons, Ltd.     

SIMS-Analyse von Wasserstoff in Si-Proben

Zusammenfassung Um die optimalen Bedingungen für den Wasserstoffnachweis in Festkörpern zu finden, wurden systematische Untersuchungen an mit Wasserstoff bzw. Deuterium implantierten Si-Proben durchgeführt. Es wurden die SIMS-Tiefenprofile analysiert, die Sputterraten gemessen und die Nachweisempfindlichkeit quantitativ ermittelt. Bei kleinen Implantationsdosen zeigt sich eine gute Übereinstimmung der gemessenen Profile mit den theoretischen Berechnungen.

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SIMS analysis of hydrogen in Si samples

Summary In order to optimize the hydrogen analysis in solids, systematic SIMS investigations on H and D implanted Si samples were made. Depth profiles obtained under different experimental conditions were discussed, sputtering yields and detection limits were determined. For low implantation doses the measured depth profiles are in good agreement with theoretically determined distributions.

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EURATOM Association     

An effect of residual gas component on detected secondary ions during TOF‐SIMS depth profiling and a method to estimate contained component

With regard to Secondary Ion Mass Spectroscopy (SIMS) measurement of atmospheric gas elements, a problem occurs that the detected signal includes background components caused by residual gas along with contained components. Relating to this issue, an available method to quantify the contained components by separating the background ones had been established for Dynamic SIMS. Time‐of‐Flight SIMS with sputtering ion gun has also applied for depth profiling as well as Dynamic SIMS. However, few studies have attempted to investigate the secondary ion behavior of the atmospheric gas elements for depth profiling by Time‐of‐flight SIMS, especially for low concentration levels. In this study, experimental examinations of the secondary ions of the atmospheric gas elements, such as oxygen, hydrogen, and carbon in the silicon substrate, has been conducted in various analytical conditions of TOF‐SIMS depth profiling mode. Under the analytical conditions of our study, it has been proved that the background intensity of these elements was correlated to the sputtering rate. For the analysis of Floating Zone Silicon substrate, the oxygen intensity of the background component was proportional to the inverse number of the sputtering rate. Based on these facts, the total detected intensity of the atmospheric gas elements was able to be separated into the contained components and background ones by changing the sputtering rate during TOF‐SIMS measurement. An experimental result has shown that the contained oxygen concentration in the Czochralsk Silicon substrate estimated by the “TOF‐SIMS Raster Change Method” has successfully agreed with the result by the Dynamic SIMS.     

Secondary-Ion Mass-Spectrometry on insulators with neutral primary particles

Summary Normally, the analysis of insulators by the SIMS method is disturbed by charge effects. The use ofneutral primary particles (SIMS/NPB) appreciably reduces these effects and makes possible the analysis of both positive and negative secondary ions without artificially changing the actual distribution of highly mobile species in the solid to be analysed.

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Sekundärionenmassenspektrometrie an Nichtleitern unter Verwendung neutraler Primärteilchen

Zusammenfassung Die Analyse von Nichtleitern mittels SIMS wird in der Regel durch Aufladungseffekte gestört. Die Verwendungneutraler Primärteilchen (SIMS/ NPB) verringert diese Effekte deutlich und ermöglicht sowohl die Analyse positiver wie negativer Sekundärionen, ohne die tatsächliche Verteilung sehr beweglicher Spezies im analysierten Festkörper künstlich zu verändern.

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Presented at the 10th Kolloquium über metallkundliche Analyse, Wien, 3.–5. November 1980. -Dedicated to Prof. Dr. Hanns Malissa on the occasion of his 60th birthday.

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On leave from: Institut für Theoretische Metallurgie, TU Clausthal, D-3392 Clausthal-Z. (Federal Republic of Germany).