Evaluation of the Distribution Depth of Charge Injected by Direct-Current Discharge Plasma into Thin Polyimide and Poly(ethylene terephthalate) Films

The dynamic capacitor method was proposed for determining the distribution depth of negative charge induced in the surface layers of thin polymer films under exposure to a dc discharge as a result of trapping plasma-injected electrons, and equations for calculation were obtained. Charge distribution in thin poly(pyromellitimide) and poly(ethylene terephthalate) films with different thickness (1–6 m) was experimentally studied, and the negative charge due to the injection of electrons from plasma was found penetrate to a depth greater than 0.5 m.     

X-ray microanalysis of thin film layered specimens containing light elements

Analysis of thin film layers on bulk substrates is carried out using a technique based on the (z) model of the depth distribution of X-ray emission. Both the composition and thickness of individual layers can be determined provided that the same element is not present in more than a single layer.The application of this method to the analysis of thin titanium-boron nitride bilayers on silicon or molybdenum substrates is discussed. X-ray intensities were measured by energy dispersive spectroscopy with a windowless or ultra thin window detector. The thickness of a 10 nm titanium layer could be estimated to within about ±1 nm, which is comparable with the depth resolution attainable by Auger sputter profiling.     

Thickness determination from the GDOS depth profiles using piece-wise linear model functions

A data processing method is presented making it possible to determine thin film thickness from GDOS depth profiles. It consists of fitting a piece-wise linear function to the depth profile and in using positions (abscissae) of their knots as parameters which are proportional to film thickness. For thickness calibration, such a linear combination of these parameters is used, which gives minimum variation coefficient of the residuals between the real and the estimated thickness of calibration samples. Relative error lower than 3% was obtained in calibration using 4 samples with nickel film thickness ranging from 0.1 to 8.3 m, each analyzed four times.     

Determination of thickness distribution and composition of thin coatings by EPMA: Application in the field of steel sheet production

A new method for the investigation of surface coatings by EPMA is presented. It is based on a physical model which takes into account the X-ray intensity depth distribution, the absorption and the electron backscattering effects at the interface between film and substrate. When combined with the concentration mapping (CM) technique, a two-dimensional film thickness distribution and the film composition can be determined simultaneously. Only bulk standards are required for this method.With some examples in the field of steel sheet production and electrogalvanizing the versatility of the method as well as its high sensitivity are pointed out. Particularly important for practical work is the applicability to almost any combinations of film and substrate materials as well as the wide thickness range from almost the total X-ray emergence depth down to the monolayer range.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Optical tomography of non-crystalline films by interference enhanced Raman spectroscopy

The depth dependence of Raman spectra of a-GeS₂-type films having a different optical thickness (/4 and /2) and their refractive index profile have been investigated. The model of a layered-inhomogeneous structure of films has been proposed. There have been distinguished three regions: near-surface region (up to 50 Å), central part and transition film-substrate region (up to 300 Å).     

The angle-resolved self-ratio technique for surface depth profile investigations by XFS,EMA, XPS and AES

The angle-resolved self-ratio (AR/SR) technique is a non-destructive, low-damage measuring technique in which the intensity I of an excited, analyte-characteristic radiation is measured as a function of the take-off angle from the surface plane for the purpose of obtaining quantitative depth information about the chosen analyte from the gradient dI/d. The depth information may be any of the following: the type of depth profile, the centroid depth of this profile, the thickness of a uniform overlayer, the stoichiometry of a uniform overlayer, the thickness of a uniform buried layer, and others. The AR/SR technique is one of a number of variants of the angle-resolved technique which is particularly suited for practical application because this mode combines an acceptable measuring effort with a simplicity and transparency of evaluation (by use of analytical formulae) not available with other procedures. The capabilities and limitations of the AR/SR technique in particular are reviewed, with special reference to four methods with which the technique has found application, viz. X-ray fluorescence spectrometry (XFS), electron microbeam analysis (EMA), X-ray photoelectron spectrometry (XPS) and Auger electron spectrometry (AES). Emphasis is placed on the role assigned to AR/SR/XFS and AR/SR/EMA in certification of ion-implanted reference materials.Invited lecture at 15th Colloquium on Materials Analysis, Wien, May 27–29, 1991     

Determination of boron by the neutron depth profile (NDP) technique for VLSI processing application

Borophosphosilicate glass (BPSG) has been used for its improved reflow properties compared to low temperature oxide (LTO) in planar technology. Thin films of BPSG were deposited by a low-pressure chemical vapor deposition process. The boron content was determined by NDP. In addition from the NDP spectrum the depth profile of boron and the thickness of the film were also determined. In the NDP technique, samples, typically silicon wafers with 500 nm thick BPSG film, were exposed to a highly-thermalized neutron beam. Generated by the¹⁰B(n,)⁷ Li reaction, isotropically emitted monoenergetic particles of 1.47 MeV were counted in an evacuated in-beam analysis setup. The energy loss of the -articles in the film was proportional to the depth at which the nuclear reaction took place. The energy spectrum of the -articles, therefore, was a direct result of the boron depth profile, and the area under the curve was a measure of the total number of boron atoms in the film. This unique nuclear technique provided an excellent method for optimizing the composition of the BPSG film for device processing.     

Depth Profile Analysis on the Nanometer Scale by a Combination of Electron Probe Microanalysis (EPMA) and Focused Ion Beam Specimen Preparation (FIB)

Electron probe microanalysis (EPMA) offers high sensitivity and high accuracy in quantitative measurements of chemical compositions and mass coverages. Owing to the low detection limits of the wavelength-dispersive technique, monolayers with mass coverages of about 0.05µgcm^–2 can be detected. Assuming a density of 5gcm^–3 this corresponds to a thickness of 0.1nm. With these advantages in mind, EPMA was extended to depth profile analysis in the sub-micron range using a surface removal technique.The present paper shows how depth profile analysis can be improved by combining EPMA and the focused ion beam (FIB) technique. The focused ion beam system uses a Ga⁺ ion beam. The ion beam allows the milling of defined geometries on the nanometer scale, so that very shallow bevels with exactly defined angles in relation to the surface can be obtained. Low surface damage is expected due to low sputtering effects. Calibrated WDX measurements along the bevel deliver quantitative concentration depth profiles. First results obtained with this new combination of methods will be presented for a multilayered sample used in optical data storage.     

Analysis of the area of material really tested by TMA

Deformation distribution within the specimen beneath the thermomechanical analysis (TMA) probe, found by using the finite element method (FEM), depends mainly on penetration depth, specimen thickness and diameter as well as on radius of the probe tip when the Poisson’s ratio influences it just slightly. For standard radius of the tip R_o=1 mm, most deformation is distributed in a material layer up to 0.5 mm thick independently on elastic modulus of a polymer at a glassy state. It is caused by the fact that maximal penetration depth for the polymers usually equals to about 0.05 mm. Because of this, the contact surface area is less than 0.17 mm² for the standard radius of the tip. This evidences that predominantly the specimen volume equal to  mm² (depth×area) is tested by the TMA at compression mode. For R_o=5 mm is tested the layer 2.5 mm thick. This makes possible to evaluate the material properties in the zone of different thickness depending on radius of the tip.     

Thickness Determination of Ultra-Thin Films on Si Substrates by EPMA

Results from thickness determination of single-element ultra-thin (<10nm) films by electron probe microanalysis (EPMA) are presented. The studied samples were Ge, Sn, Ag and Au thin films deposited by resistive evaporation on Si substrates. The thickness of the films was controlled during evaporation by means of a quartz crystal, previously calibrated using samples with overlayers of different thicknesses (>20nm) measured by Rutherford backscatter spectrometry and optical interferometry. EPMA measurements were performed on an electron microprobe CAMECA SX-50, with incident electron energies ranging from 4keV to 20keV. Film thicknesses were derived from the measured k-ratios using the analytical programs X-Film and Layerf and the Monte Carlo simulation code Penelope. The ionization cross sections used in the simulations were calculated with the distorted-wave Born approximation. Film thicknesses obtained from the EPMA measurements using the various computational methods are compared with those measured with the quartz crystal. The maximum relative difference between results from the different techniques does not exceed 5%.     

AES investigations of plasma sprayed Al2O3 coatings on Ni

Summary The system of plasma sprayed Al₂O₃ on Ni substrates is investigated by means of AES/depth profiling. The influence of two process parameters — preoxidation procedure and spraying temperature — is examined. Rupture between substrate and ceramic layer occurs between a residual — or, in the case of excessive preoxidation, a superfluous — NiO layer on Ni, the thickness of the former depending on preoxidation conditions and the Al₂O₃ layer, the back side of which being partially covered with NiO. The thickness of this NiO layer increases up to about 1 m with the thickness of the initial NiO layer on the substrate, until this layer is about 1.3 m thick, and remains constant thereafter. The same dependence is observed for the width (0.1–1 m range) of the mixed oxide interface between the sprayed Al₂O₃ layer and the NiO layer below. These results represent the chemical contribution to adherence. Contrary to excessive preoxidation, an increase of the spraying temperature from 300°C to 500°C effects broader interfaces.This poster was awarded the First Prize in Poster Section C by the Deutscher Arbeitskreis für Spektroskopie (DASp)     

Accuracy of film thickness determination in electron probe microanalysis

The thickness of copper films (100–450 nm) on silicon substrates was determined by electron probe microanalysis (EPMA) applying (z) procedures of Pouchou and Pichoir. Film thickness was calculated from experimental k-ratios analyzed with electron energies between 6 and 30 keV using commercial software (LAYERF distributed by CAMECA). The influence of the incident electron energy and X-ray line chosen for analysis on the results was investigated. Accuracy of film thickness determination was evaluated by comparison with Rutherford backscattering spectroscopy (RBS) and secondary ion mass spectrometry (SIMS). The difference between layer thicknesses determined with EPMA and RBS is in general less than 2%, if EPMA measurements are performed with various electron energies. Layer thicknesses determined with Cu-L are mostly closer to values obtained by RBS than those derived from Cu-K radiation. Preliminary SIMS measurements yielded inconsistent results and, thus, cannot be used in this case to determine the layer thickness of Cu films on Si accurately.     

Depth-profiling of organic layers on microparticles with SNMS

Summary Previous work on the quantification and localization of organically bound elements with plasma-based SNMS for the characterization of microparticles has been continued. Relative detection factors for 10 elements have been determined. Except for lead and bromine a principle proportionality to atomic ionization probabilities is shown. A moderate matrix dependence of less than 40% variation was found even when inorganic and organic materials are included. For depth calibration, erosion rates of organic materials were determined from the time interval necessary to sputter through planar single-layers and Langmuir-Blodgett multi-layer systems with known thickness, as well as from gravimetric powder measurements. Depth propagation rates were 0.7 nm·sec^–1 for polymers and 2.3 nm·sec^–1 for aromatic compounds, when 400 eV argon ion bombardment with 0.7 mA·cm^–2 was used. A depth resolution of 30 nm has been obtained. Model particles of 5 m size have been coated with fluoranthene. Inspection with SNMS revealed an incomplete coating covering only 20% of the microparticle surface with an average thickness of the partial coating of 300 nm. Subsequent characterization using laser-induced fluorimetry confirmed the amount of fluoranthene coating measured by SNMS.     

Depth profiling with modified dc-Grimm and rf-Grimm-type glow discharges operated with high gas flow rates and coupled to a high-resolution mass spectrometer

The improved analytical capability of direct-current (dc) and radiofrequency (rf) fast flow glow discharges coupled to a sector field mass spectrometer (GD-SFMS) are presented. In particular, the effect of GD chamber design has been studied to obtain suitable crater shapes for depth-profile analysis of solid samples while maintaining the high sensitivity and stability of this source. In this study it was observed that the distance between the sample surface and the end of the flow tube is critical and so careful optimisation is needed. Under optimum conditions plane crater profiles, with high ion-signal sensitivity and sufficient stability, were obtained. The capability to determine qualitative and semi-quantitative depth profiles is presented here using, as model, a coated sample of certified thickness. Finally, the depth resolution achieved for qualitative depth profiles obtained by rf-GD-(SF)MS is compared with that for the well-established rf-GD optical emission spectroscopy (OES) technique.Dedicated to the memory of Wilhelm Fresenius     

Nitrogen depth distribution, interface and structure analysis of SiNx layers produced by low-energy ion implantation

Thin silicon nitride (SiN _x ) layers with the stoichiometric N/Si ratio of 1.33 in the maximum of the concentration depth distributions of nitrogen were produced by implanting 10 keV¹⁵N ₂ ⁺ in 100 silicon at room temperature under high vacuum conditions. The depth distribution of the implanted isotope was measured by resonance nuclear reaction analysis (NRA), whereas the layer structure of the implanted region and the geometrical thickness of the layers were characterised by high resolution transmission electron microscopy (TEM). SiN _x layers with a thickness of about 30 nm were determined by NRA. Channeling Rutherford backscattering spectrometry was used to determine the disorder in the silicon substrate. Sharp interfaces of a few nanometers between the highly disordered implanted region and the crystalline structure of the substrate thickness were observed by TEM. The high thermal stability of SiN _x layers with N/Si ratios from under to over stoichiometric could be shown by electron beam rapid thermal annealing (1100 °C for 15 s, ramping up and down 5 °C/s) and NRA.     

Contribution of adsorption to retention data in glass capillary gas chromatography part. I. Polar stationary phases

Summary The influence of the film thickness of Carbowax 20M coated onto glass surfaces (series of columns with different mode of surface treatment) upon the retention indices of solutes which exhibit tendency to hydrogen bonding has been investigated. Limiting values of Kovats indices, I, are calculated for all the columns examined.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Comparative plasma SNMS and AES measurements on ceramic powders and fibres

SNMS depth profiles of layers of 0.4–0.8 m sized Si₃N₄, BN and partly SiC-coated B₄C powder particles and of 10 m sized SiC fibres are obtained without great expenditure on time and specimen preparation. Close contact with Au foil provides for electrical conductivity. Averaged depth profiles of a great number of particles or fibres are obtained. AES serves as a comparative method; the carrier-gas heat extraction (inert gas fusion) technique is used for the semiquantification of OH signals in SNMS. Esterification of surface OH with ethanol during suspension is not detectable. Hydrolyzation or oxidation reactions having penetrated through the bulk of BN particles cause qualitatively different depth profiles than found on Si₃N₄ particles carrying a nm thin natural (hydr-)oxidic layer. The effects of preparative surface reactions like additive coating (SiC on B₄C particles), etching and oxidation (of SiC fibres) can be monitored. Quantification attempts yield standard deviations between 10 and 50%.Presented on the 15. Kollquium über Werkstoffanalytik, Vienna, May 27–29, 1991     

Analysis of welds of offshore steels

In offshore technology the quality of weldments is of great importance. In certain cases special electrodes are being used for underwater weldments whereas in different procedures a habitat is built around the weld joint in order to facilitate dry welding for a given water depth (pressure). Of course a number of weld material quality problems results from this.With the purpose of optimizing the quality of such weldments different parameters like oxygen content, its distribution in the inclusions as well as the inclusion distribution itself have to be analyzed and correlated to mechanical properties. This is done with the help of SNMS, heat extraction and SEM systems.Dedicated to Professor Günther Tölg on the occasion of his 60th birthday     

Molecular ion implantation in silicon

¹⁵N₂ ⁺ molecular ions were implanted with 10keV (j=10 A/cm²) under high vacuum conditions close to room temperature in 100 silicon (c-Si) to study the¹³N depth distributions, particularly the dependence of peak concentration and dose on the ion fluence. The analysis were performed by the resonant nuclear reaction¹⁵N(p, )¹²C(NRA). A maximum peak concentration of 65 at.% was measured. Thin stoichiometric silicon nitride layers with a thickness of approx. 20 nm (15 at.% nitrogen at the specimen surface) were produced by this low-energy implantation of¹⁵N₂ ⁺ ions with an ion fluence of 1.5·10¹⁷ ions/cm². NRA analysis of 38 keV¹⁵N₂ ⁺ and 19keV¹⁵N⁺ ion implantations were performed to compare the¹⁵N depth distributions. No significant changes in the depth distributions are measured, that means, the molecular¹⁵N₂ ⁺ ions are already disintegrated passing the very first atomic layers of the sample during implantation. Non-Rutherford RBS with⁴He⁺ ions and 3.45 MeV was performed in order to confirm the results obtained by NRA.Dedicated to Professor Dr. rer.nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday