Peter Wilhartitz

Classical analysis including trace-matrix separation versus solid state mass spectrometry: A comparative study for the analysis of high purity Mo, W and Cr

The applicability of GDMS, SIMS, SSMS, NAA and TMS with AAS, ICP-OES and ICP-MS end determination for routine bulk ultratrace analysis of high purity refractory metals was investigated. Due to the heterogeneous distribution of trace elements in the sub-ppm range, sample consumption and analysis time have a tremendous influence on quantification with procedures of low sample consumption. As an example, GDMS, which is commonly used for ultrapure material certification by most of the manufacturers in Europe and the USA, exhibits discrepancies by more than one order of magnitude for repetitive analyses of a series of trace components in the same sample. Furthermore, results of different laboratories using the same instrument are frequently not comparable. Due to easy standardization and large sample consumption TMS procedures combined with FAAS, GFAAS, ICP-AES and ICP-MS as methods of end determination exhibit better precision and accuracy than GDMS and SIMS. Detection limits are comparably low or even better in case of ICP-MS end determination. TMS procedures are less expensive and less time consuming than highly sophisticated analytical techniques like GDMS, SIMS or NAA. Additionally, they can be easily applied by experienced personnel in a well equipped industrial analytical laboratory.

Statistical evaluation of refractive index, growth rate, hardness and Young's modulus of aluminium oxynitride films

Abstract Aluminium oxynitride films were produced by reactive dc-magnetron sputtering with compositions covering the concentration range from nitride to oxide. The altered deposition parameters were the sputtering power and the gas flow rates of argon, nitrogen and oxygen. The refractive index and the growth rate of the films were determined by spectroscopic ellipsometry, which showed negligible absorption. With indentation by a nano hardness tester the hardness and the Youngs modulus of the films were obtained. The results of these measurements were evaluated by statistical software. The dependences of the physical properties on the deposition parameters and on the film thickness were evaluated and quantified. The thickness still had some influence on the results of the nano-indentation measurements resulting from the influence of the substrate. Furthermore, the dependences of the physical properties on the film composition represented by the oxygen content and the film thickness were evaluated. However, these evaluations only delivered useful results for the refractive index and the hardness. It is shown that the physical properties of aluminium oxynitride films can be controlled by utilising design of experiment and evaluation with statistical software, delivering the correct deposition parameters. For all of the mentioned properties graphs are given depicting actual measurement results of 26 evaluated films.

Can oxygen stabilize chromium nitride?—Characterization of high temperature cycled chromium oxynitride

Stoichiometric CrO0.1N0.9 and CrO0.5N0.5 films were produced by r.f.-sputtering. Both compositions showed CrN (Fm-3m) structure in XRD. HT-XRD measurements during heat cycling up to 850 °C revealed a region of thermal healing of structural defects during the first heat cycle. For the oxygen rich films, a relevant reduction of crystallite size expansion during heating compared to the low oxygen film was observed, while both films did show no change in crystallite size in following cycles. An explanation for this behavior could be oxynitride formation during film deposition. This was proven by STEM pictures, which indicate amorphous oxygen rich films and a columnar structure for films with low oxygen contents. In addition, EELS (ELNES) spectra give evidence for oxynitride bonding. SIMS depth profiling revealed homogeneous films with a thin protective oxide layer on the surface. In XRD, Cr2O3 was only detected after high temperature treatment and also in FT-IR no absorption band at the corresponding values, but a wide band at higher wave numbers was detected. CGHE measurements point toward only one chemical state for oxygen in the films. UPS and XPS measurements after careful sputter etching of the surface oxidation layer deviate strongly from reference CrN spectra. The Cr 2p line is shifted to higher binding energies in the oxygen rich films. No Cr2O3 contribution to the spectra was observed. The O 1s line is shifted to higher binding energies in the oxygen rich films, too, and indicates NCrO bonds. All the gained analytical information confirms the assumption of an oxynitride structure, which is known to stabilize amorphous films against recrystallization at elevated temperatures also for other compounds. No confirmation was found for the deposition of a two-phase CrN and Cr2O3 system.

High performance ultra trace analysis in molybdenum and tungsten accomplished by on-line coupling of ion chromatography with simultaneous ICP-AES

For the characterisation of trace elements in high purity Mo and W analytical methods with a detection limit in the ng/g-range have to be used. Today mass spectrometric methods are state of the art for such applications. However, these methods in case of refractory metal analysis are time consuming, expensive, limited by isobaric interferences and therefore not very suitable for quality control in an industrial laboratory. With respect to these drawbacks a cost and time efficient method was developed by on-line coupling of an ion chromatographie system to a simultaneous ICP-AES (Inductively Coupled Plasma — Atomic Emission Spectrometry) instrument. Within the limitations caused by the hard- and software of the system all parameters such as eluent concentration and flow rate, nebulizer and plasma gas flow, sampling frequency, integration time and the number of simultaneously measured emission lines were optimised. Further enhancement of the sensitivity was achieved by the use of an ultrasonic nebulizer pushing the detection limits down to the pg/g- and ng/g-range for 22 representative elements.

High performance analytical characterization of refractory metals

It is first shown what effects trace impurities generally exert on metal properties and why trace analysis is essential to modern applications of refractory metals in todays high technology. The effect of trace impurities in metals on complex systems like microelectronic components is also discussed.It is then shown, what principal analytical requirements are mandatory for trace characterization of refractory metals at levels of rising purity (4 N to 6 N). A survey of analytical methods for trace and ultratrace characterization of refractory metals is given including the following methods: flame and graphite furnace atomic absorption spectrometry, ICP and DCP-atomic emission spectrometry, X-ray fluorescence spectrometry, activation analysis, mass spectrometric methods, especially SIMS and GDMS.

Ultratrace and microdistribution analysis in material sciences

SummaryAll-rounders and experts are two basic types of scientists. A harmonic cooperation between these two groups is essential for todays large study groups engaged in materials development. Materials development programmes in many high-tech countries are major fields of research supported by special financial arrangements (e.g. COST, EURAM or BRITE-programmes in Europe). Modern materials development is not possible without analytical guidance. This is not always realized by all engaged partners and it is a main obligation of analytical chemists to make aware of the role of a potent materials characterization in relevant development programmes. This should be demonstrated in two essential relevant areas: a) Bulk trace and ultra trace analysis of metals. Many important metal properties are directly or indirectly influenced by trace elements. In complex systems like fusion reactors or microelectronic components, trace contents of even minor metal parts might decisively influence system properties. As refractory metals and their silicides gain rising importance in VLSI microelectronic applications, their ultratrace characterization becomes a major challenge. Essential progress was possible by the complementary application of mass-spectrometric methods. Latest results and a critical survey will be given, including GDMS, SIMS, SSMS, IDMS and ICP-MS.Surprisingly, however, highest sensitivities and best detection limits were recently achieved by a combination of trace-matrix separation procedures and final end determination with ICP-MS. This combination also proved to be the most economic and safest approach from the view point of accuracy and precision. b) The analytical characterization of discontinuities and heterogeneities in solid matter. Practical examples are again taken from the study of refractory and hard metals and ceramics. A survey is given as to the manifold effects, heterogeneities and discontinuities exert on modern high-tech materials: as a function of their average diameter, they can either strengthen the material (dispersion strengthening), or they can cause deterioration of material properties e.g. as points of crack initiation, by grain boundary embrittlement etc. Together with most important methods for detection and characterization of heterogeneities and discontinuities, their evaluation and possible prevention during materials fabrication are discussed and pertinent examples are given. The phenomena of heterogeneous particles and pores are elucidated in more detail.

Critical evaluation of the state of the art of the analysis of light elements in thin films demonstrated using the examples of SiO X N Y and AlO X N Y films (IUPAC Technical Report)

The quantitative analysis of thin films containing light elements is very important in improving the coating processes and technological properties of the products. In order to review the state of the art of modern analytical techniques for such applications, the model systems SiOXNY and AlOXNY were selected. Over 1000 abstracts were screened, and the relevant literature was evaluated to give a comprehensive overview of instruments, analytical procedures and results, film types, deposition methods, and investigation goals. From more than 150 citations, the limitations, drawbacks, and pitfalls of the different methods were extracted and reviewed critically, while in addition, improvements were proposed where possible. These suggestions are combined with the newest results of investigation by the authors of this paper. Recommendations concerning the optimized combination of analytical methods for different analytical problems have been worked out on the basis of all results. Analysis of various multicomponent systems containing light elements demonstrated the applicability of the different methods of analysis in combination to all film systems with related compositions.

The characterization of high-tech materials : perspectives, challenges, trends

From the Stone Age on, developmental periods of mankind carry the names of materials. Materials determine the applicability of key technologies and these are in turn of major significance for the economic success and the social development in modern society. Todays high-tech materials are the consequence of an improved understanding of the structure and composition of matter and of the interplay of microstructure and minor and trace constituents. We can distinguish four basic dimensional structural categories of materials: (a) the atomic structure level; (b) the crystal, glassy or amorphous structural level; (c) the microstructural level; (d) the level of constructions. As an example, these structural levels are described in some detail for graphite, a material used extensively throughout Analytical Chemistry. Decisive differences at the microstructural level result in graphitic materials with very varying properties: polycrystalline electrographite, glassy carbon, and pyrolytic graphite. Examples for the use of these materials in ETAAS are discussed.Structural features together with topochemical and trace chemical characteristics are studied today by a wide variety of analytical instrumentation and methods of modern materials analysis which can be grouped into four categories of techniques: (a) photon probe techniques; (b) electron probe techniques; (c) ion probe techniques; (d) electrical field probes.The most important of those techniques are discussed shortly with respect to their main characteristics as lateral and depth resolution, detection sensitivity, additional bonding or structural information, depth profiling possibilities etc.The constructions are the ultimate level of a materials structure. Structures of microelectronic components reach dimensionally into the domain of microstructure whereas constructions in heavy industry are of meter-ton dimensions. Progress in the use of materials as carriers of information is visualized by a morphological comparison of the sound tracks of conventional records with the information imprinted in optical discs.It is important to conceive materials as dynamic systems with limited lifetime. Fatigue and recrystallization are prominent relevant phenomena which must be studied by microstructural and topochemical methods. Dispersion strengthened microalloys like TZM, HT-molybdenum and NS-tungsten are discussed as examples how materials can be improved with respect to their extended use under extreme conditions. Again, a thorough structural and topochemical characterization was the basis of a successful respective materials development although a multitude of relevant topochemical questions still remain to be solved.Lifetime investigations are an essential tool of materials development as well as quality control. Relevant investigations for various tube materials for ETAAS are discussed.

Analysis of tantalum by ICP-AES involving trace-matrix separation

SummaryA trace-matrix separation technique for the analysis of high-purity tantalum by ICP-AES has been developed to overcome the difficulties caused by the line-richness of this matrix. The procedure is based on the extraction of tantalum with diantipyrylmethane from 12 mol/l HF in dichloroethane. The extraction behaviour of 35 elements has been investigated from which 25 can quantitatively be separated with a residual matrix concentration <0.01% at 1 g sample portion. The achievable limits of detection for ICP-AES are between 0.02 μg/g and 10 μg/g. The method was applied to the analysis of a high-purity tantalum sample. For a number of elements, the results of this technique are compared with those of other techniques whereby, in general, a good agreement was achieved.

Multielement ultratrace analysis in tungsten using secondary ion mass spectrometry

SummaryThe 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.