Quantitative Depth Profile Analysis Research Articles

Quantitative depth profile analysis using short single pulse responses in LA-ICP-Q-MS experiments

The measurement of single pulse responses (SPRs) in LA-ICP-Q-MS measurements was optimized to analyze more than one m/z ratio.

Resonant Laser Induced Breakdown Spectroscopy for quantitative elemental depth profile analysis of WTa coating

This work reports on the procedure of Resonant-LIBS, in which ablation and subsequent excitation is achieved by fine-tuning an Optical Parametric Oscillator (OPO) laser to the resonant transition of tungsten (W I) at 255.14 nm and analyzing the optical emission spectroscopy results. Compared to conventional LIBS, the ablation rate is significantly reduced in the resonant regime, resulting in finer resolution of depth profiles. This reduction in ablation rate can be attributed to a process called Resonance Laser Ablation (RLA) where a part of the laser energy is employed for ablation, while the rest is dedicated to resonant excitation. The sample under consideration is a WTa-coated (7μm) Mo substrate prepared by a dual magnetron sputtering system. These efforts are motivated by the need for improvement in quantitative depth analysis of W-based Plasma-Facing Components (PFC). Particularly to target the undesirable surface modifications due to the interaction with H isotopes in fusion plasma, such as fuel retention or erosion/deposition.

Analysis of Different Complex Multilayer PACVD Coatings on Nanostructured WC-Co Cemented Carbide

The development of cemented carbides nowadays is aimed at the application and sintering of ultrafine and nano-sized powders for the production of a variety of components where excellent mechanical properties and high wear resistance are required for use in high temperature and corrosive environment conditions. The most efficient way of increasing the tribological properties along with achieving high corrosion resistance is coating. Using surface processes (modification and/or coating), it is possible to form a surface layer/base material system with properties that can meet modern expectations with acceptable production costs. Three coating systems were developed on WC cemented carbides substrate with the addition of 10 wt.% Co using the plasma-assisted chemical vapor deposition (PACVD) method: single-layer TiN coating, harder multilayer gradient TiCN coating composed of TiN and TiCN layers, and the hardest multilayer TiBN coating composed of TiN and TiB2. Physical and mechanical properties of coated and uncoated samples were investigated by means of quantitative depth profile (QDP) analysis, nanoindentation, surface layer characterization (XRD analysis), and coating adhesion evaluation using the scratch test. The results confirm the possibility of obtaining nanostructured cemented carbides of homogeneous structure without structural defects such as eta phase or unbound carbon providing increase in hardness and fracture toughness. The lowest adhesion was detected for the single-layer TiN coating, while coatings with a complex architecture (TiCN, TiBN) showed improved adhesion.

Wear Rate Evaluation of Sol-Gel TiO2-ZrO2 Films by Quantitative Depth Profile Analysis

Wear Rate Evaluation of Sol-Gel TiO2-ZrO2 Films by Quantitative Depth Profile Analysis

Quantitative depth profile analysis of InP/InGaAs hetero-interfaces by as carry-over

Although it is important to investigate the hetero-interface of III-V semiconductor devices for highly efficient solar cell or photo-detector, it is not trivial to measure structural property at interface due to problems related to thickness and small compositional variation of interface layer to clearly observe current measurement systems. In this study, to investigate the interfaces of InP/InGaAs structures grown on InP substrates, two different samples were prepared. One was grown at lattice parameter of InP and InGaAs matched condition. The other has arsenic contained interface between InP/InGaAs leaving growth interruption process out. It was found that the InP capping layer without growth interruption included about 1% of arsenic due to arsenic carry-over. For depth profiling analysis using HRXRD, we developed the combinational method of InP selective etching technique and HRXRD. As a result, we could successfully demonstrate that the compositionally graded interface that generated from arsenic carry-over could be quantified. We also reveals approximately 170 nm thickness of interface layer which is thicker than generally reported values originated from residual arsenic in deposition chamber.

Quantitative depth-profile analysis of transition metal nitride materials with combined grazing-incidence X-ray fluorescence and X-ray reflectometry analysis

Refractory transition metal nitrides are attracting attention in many microelectronics research and development fields. Their different applications and desired performances require a precise control of the film thickness and elemental depth profile. This information can be non-destructively obtained combining Grazing-Incidence X-ray Fluorescence (GIXRF) and X-ray Reflectometry (XRR) analysis. GIXRF-XRR joint analysis can be performed following a reference-free approach, which requires the knowledge of the whole experimental system. However, such a rigorous metrological approach cannot be easily applied to in-lab or in-fab tools due to the difficulty to access the various experimental set-up parameters, therefore another approach is needed.In this paper, we used a reference-based method consisting in the use of known standard samples, close in composition and structure with respect to the samples to analyse, to deduce the key parameters of the instrumental setup. These are then used to perform quantitative GIXRF-XRR combined analysis of the samples of interest. We applied this method to titanium tungsten nitride thin films elaborated by Physical Vapour Deposition (PVD). Our results show that the reference-based method, using carefully determined instrumental functions, can meet the requirement for both qualitative and quantitative depth-profiling analysis. The reference-based approach result easier to implement into labs and fabs than the reference-free method.

Characterization of arsenic plasma doping and postimplant processing of silicon using medium energy ion scattering

Plasma doping (PLAD) is increasingly applied in microelectronic device manufacture to produce high throughput, high fluence implants. In this medium energy ion scattering (MEIS) study of the PLAD process, Si(100) wafers were exposed to an As containing plasma while pulse biased negatively to 7 kV to cause (recoil) implantation and deposition of As. Quantitative MEIS depth profiling analysis in conjunction with energy spectrum simulation was applied to characterize the near-surface layer changes of the Si wafer following (i) the PLAD process, (ii) two types of chemical wet clean (oxidizing and nonoxidizing), and (iii) spike annealing in an N2 atmosphere. MEIS analysis showed that the PLAD process produced an intermixed As/Si layer, with a near-surface As content of ∼40% that decayed almost linearly to near-zero at a depth of ∼17 nm. This mixed As/Si layer was unstable in air and the initially recorded 1.2 nm thick oxide cap layer grew over a period of four months to 3.5 nm with a concurrent 25% As loss by sublimation. The application of the industry standard, oxidizing wet chemical clean removed the top As and concurrently produced a ∼14 nm thick Si oxide above the remaining implanted As profile, which matched the tail of original As implant profile. As depth profiles measured for the 7 kV PLAD process after a wet clean and spike annealing showed solid phase epitaxial regrowth of the disordered layer. A detailed comparison of the random and aligned MEIS spectra yielded depth profiles of substitutional As with a concentration in excess of 1 × 1021 As cm−3 over a depth greater than 10 nm. The retained dose of 1.35 × 1015 cm−2 represents a ∼70% increase in substitutional As compared to that recorded after a nonoxidizing clean. Such an alternative wet chemical clean, in which Si reoxidation did not occur, was applied to determine the depth of the mixed As/Si layer removed. Found to be 7 nm, the analysis indicated that the etching process ceased when the Si concentration reached 4 × 1022 cm−3. After spike annealing, part of the remaining As had segregated in a thin layer under a 1.6 nm thick surface oxide. The retained As dose in this case was 8 × 1014 cm−2, equivalent to a 1% As substitutional dopant concentration to a depth of ∼14 nm. Different substitutional As doses measured with MEIS were found to correlate closely with sheet resistance measurements, confirming that equating the substitutional As with the active As dose remains correct for these ultrashallow profiles, typically 10 nm deep.

Bevel depth profiling by high-spatial-resolution sputtered neutral mass spectrometry with laser postionization

Secondary-ion mass spectrometry (SIMS) sputter depth profiling is used for the quantitative depth profile analysis of impurities. However, SIMS suffers from a large quantitative uncertainty and depth-scale uncertainty at the interfaces of heteromultilayers and in the near-surface region, because the secondary ion yield and sputtering yield are significantly influenced by matrix effects and accumulation effects of the primary ion. In this paper, the authors report on the development of a new depth profiling method with good depth-scale accuracy and low matrix effects to overcome these problems. This was achieved through the combination of high-spatial-resolution bevel depth profiling and sputtered neutral mass spectrometry with laser postionization (laser-SNMS). The sample used to evaluate this new bevel depth profiling method was a silicon on insulator wafer obtained using the separation by implantation of oxygen technique and implanted with boron. Depth profiles were obtained using both SIMS and laser-SNMS and evaluated by comparison with the stopping and range of ions in matter (SRIM) simulation. Although both methods afforded quite good depth resolutions, in SIMS the secondary ion signal intensity for boron was amplified by the influence of the matrix effect and showed a discontinuous profile shape at the interfaces, whereas the profile for boron obtained using laser-SNMS was consistent with the SRIM results and exhibited high continuity. By using a combination of the bevel depth profiling method and laser-SNMS method, it was confirmed that an easy-to-analyze depth profile could be obtained for the dopant concentration in multilayer samples, which is difficult to obtain using the conventional SIMS method.

Evaluation of different strategies for quantitative depth profile analysis of Cu/NiCu layers and multilayers via pulsed glow discharge – Time of flight mass spectrometry

There is still a lack of approaches for quantitative depth-profiling when dealing with glow discharges (GD) coupled to mass spectrometric detection. The purpose of this work is to develop quantification procedures using pulsed GD (PGD) - time of flight mass spectrometry. In particular, research was focused towards the depth profile analysis of Cu/NiCu nanolayers and multilayers electrodeposited on Si wafers. PGDs are characterized by three different regions due to the temporal application of power: prepeak, plateau and afterglow. This last region is the most sensitive and so it is convenient for quantitative analysis of minor components; however, major elements are often saturated, even at 30W of applied radiofrequency power for these particular samples. For such cases, we have investigated two strategies based on a multimatrix calibration procedure: (i) using the afterglow region for all the sample components except for the major element (Cu) that was analyzed in the plateau, and (ii) using the afterglow region for all the elements measuring the ArCu signal instead of Cu. Seven homogeneous certified reference materials containing Si, Cr, Fe, Co, Ni and Cu have been used for quantification. Quantitative depth profiles obtained with these two strategies for samples containing 3 or 6 multilayers (of a few tens of nanometers each layer) were in agreement with the expected values, both in terms of thickness and composition of the layers.

Towards Structural Analysis of Polymeric Contaminants in Electrodeposited Cu films

The incorporation of plating additives into Cu films was studied by means of complementary Laser Ablation/Ionization Mass Spectrometry (LIMS) and Secondary Ion Mass Spectrometry (SIMS) depth profiling techniques combined with Focused Ion Beam (FIB) analysis.Cu test samples were electrodeposited in the presence of a new prototypical two-component additive package for advanced Damascene applications consisting of a hybrid-type suppressor additive (Imep: polymerizate of epichlorohydrin and imidazole) and its essential co-additive (SPS: bis-(sodium-sulfopropyl)-disulfide). The tunable non-linear interplay between the Imep and the SPS during oscillatory Cu electrodeposition is used to fabricate samples bearing spatially confined layers with sequential high and marginal additive embedment. These test samples constitute an excellent platform to conduct true quantitative chemical depth profiling analysis of electrodeposited Cu films. In particular LIMS depth profiling measurements with an unmatched nano-meter depth-resolution demonstrate a preferential inclusion and accumulation of contaminants at grain boundaries inside the Cu deposit whereas the Cu grains remain largely contamination-free. A novel LIMS desorption approach is presented which allows for a molecular structure analysis of the polymeric additive ensembles preferentially embedded at grain boundaries of the Cu deposit. Our LIMS analysis confirms a recently discussed mechanism on the action of these hybrid additives which relies on their interaction with thiolate-stabilized Cu(I) intermediates.

Influence of nitriding on corrosion resistance of martensitic X17CrNi16‐2 stainless steel

Nitriding increases surface hardness and improves wear resistance of stainless steels. However, nitriding can sometimes reduce their corrosion resistance. In this paper, the influence of nitriding on the corrosion resistance of martensitic stainless steel was investigated. Plasma nitriding at 440 °C and 525 °C and salt bath nitrocarburizing were carried out on X17CrNi16‐2 stainless steel. Microhardness profiles of the obtained nitrided layers were examined. Phase composition analysis and quantitative depth profile analysis of the nitrided layers were preformed by X‐ray diffraction (XRD) and glow‐discharge optical emission spectrometry (GD‐OES), respectively. Corrosion behaviour was evaluated by immersion test in 1% HCl, salt spray test in 5% NaCl and electrochemical corrosion tests in 3.5% NaCl aqueous solution. Results show that salt bath nitrocarburizing, as well as plasma nitriding at low temperature, increased microhardness without significantly reducing corrosion resistance. Plasma nitriding at a higher temperature increased the corrosion tendency of the X17CrNi16‐2 steel.

Pulsed radiofrequency glow discharge time of flight mass spectrometry for coated glass analysis

The potential of rf-PGD-ToFMS for quantitative depth profiling analysis of thin layers on glasses has been investigated.

Rf-GD-OES（高周波グロー放電発光分析）による薄膜の深さ方向定量分析

rf-GD-OES（高周波グロー放電発光分析）による薄膜の深さ方向定量分析

Nondestructive atomic compositional analysis of BeMgZnO quaternary alloys using ion beam analytical techniques

The atomic composition with less than 1–2atom% uncertainty was measured in ternary BeZnO and quaternary BeMgZnO alloys using a combination of nondestructive Rutherford backscattering spectrometry with 1MeV He+ analyzing ion beam and non-Rutherford elastic backscattering experiments with 2.53MeV energy protons. An enhancement factor of 60 in the cross-section of Be for protons has been achieved to monitor Be atomic concentrations. Usually the quantitative analysis of BeZnO and BeMgZnO systems is challenging due to difficulties with appropriate experimental tools for the detection of the light Be element with satisfactory accuracy. As it is shown, our applied ion beam technique, supported with the detailed simulation of ion stopping, backscattering, and detection processes allows of quantitative depth profiling and compositional analysis of wurtzite BeZnO/ZnO/sapphire and BeMgZnO/ZnO/sapphire layer structures with low uncertainty for both Be and Mg. In addition, the excitonic bandgaps of the layers were deduced from optical transmittance measurements. To augment the measured compositions and bandgaps of BeO and MgO co-alloyed ZnO layers, hybrid density functional bandgap calculations were performed with varying the Be and Mg contents. The theoretical vs. experimental bandgaps show linear correlation in the entire bandgap range studied from 3.26eV to 4.62eV. The analytical method employed should help facilitate bandgap engineering for potential applications, such as solar blind UV photodetectors and heterostructures for UV emitters and intersubband devices.

Depth profile analysis of amorphous silicon thin film solar cells by pulsed radiofrequency glow discharge time of flight mass spectrometry.

Among the different solar cell technologies, amorphous silicon (a-Si:H) thin film solar cells (TFSCs) are today very promising and, so, TFSCs analytical characterization for quality control issues is increasingly demanding. In this line, depth profile analysis of a-Si:H TFSCs on steel substrate has been investigated by using pulsed radiofrequency glow discharge-time of flight mass spectrometry (rf-PGD-TOFMS). First, to discriminate potential polyatomic interferences for several analytes (e.g., (28)Si(+), (31)P(+), and (16)O(+)) appropriate time positions along the GD pulse profile were selected. A multi-matrix calibration approach, using homogeneous certified reference materials without hydrogen as well as coated laboratory-made standards containing hydrogen, was employed for the methodological calibration. Different calibration strategies (in terms of time interval selection on the pulse profile within the afterglow region) have been compared, searching for optimal calibration graphs correlation. Results showed that reliable and fast quantitative depth profile analysis of a-Si:H TFSCs by rf-PGD-TOFMS can be achieved.

A path towards a better characterisation of silicon thin‐film solar cells: depth profile analysis by pulsed radiofrequency glow discharge optical emission spectrometry

ABSTRACTThe analytical potential of radiofrequency pulsed glow discharge optical emission spectrometry (rf‐PGD‐OES) is investigated for quantitative depth profiling analysis of thin‐film solar cells (TFSC) based on hydrogenated amorphous silicon (a‐Si:H). This method does not require sampling at ultra‐high‐vacuum conditions, and so it facilitates higher sample throughput than do reference techniques. In this paper, the determination of compositional depth profiles of a‐Si:H TFSC was performed by resorting to a multi‐matrix calibration procedure. For this purpose, certified reference materials, as well as laboratory standards based on individual layers of doped a‐Si:H, were simultaneously employed to build the analytical calibration curves. Results show that rf‐PGD‐OES allows us to discriminate the different layers of photovoltaic devices: the front contact composed by ZnO:Al2O3 (AZO), the a‐Si:H layer (the B‐doped, intrinsic a‐Si:H and P‐doped films), the AZO/Al back contact and substrate. A good agreement with the nominal values for element concentrations (e.g. 0.4% of H, 1.5% of B and 3.7% of P) and layer thicknesses (in the range of 950 nm for the front contact and 13 nm for the P‐doped a‐Si:H layer) was obtained, demonstrating the ability of rf‐PGD‐OES for a direct, sensitive and high‐depth‐resolution analysis of photovoltaic devices. Moreover, diffusion processes between the coating layers, which could have an important influence on the final efficiency of TFSC, can be identified as well. Hence, the findings support the use of rf‐PGD‐OES as an analysis method in the development of photovoltaic thin films. Copyright © 2013 John Wiley & Sons, Ltd.

Quantitative depth profile analysis of metallic coatings by pulsed radiofrequency glow discharge optical emission spectrometry

In recent years particular effort is being devoted towards the development of pulsed GDs because this powering operation mode could offer important analytical advantages. However, the capabilities of radiofrequency (rf) powered glow discharge (GD) in pulsed mode coupled to optical emission spectrometry (OES) for real depth profile quantification has not been demonstrated yet. Therefore, the first part of this work is focussed on assessing the expected advantages of the pulsed GD mode, in comparison with its continuous mode counterpart, in terms of analytical emission intensities and emission yield parameters. Then, the capability of pulsed rf-GD-OES for determination of thickness and compositional depth profiles is demonstrated by resorting to a simple multi-matrix calibration procedure. A rf forward power of 50 W, a pressure of 600 Pa, 1000 Hz pulse frequency and 50% duty cycle were selected. The quantification procedure used was validated by analysing conductive layers of thicknesses ranging from a few tens of nanometer up to about 20 μm and varied compositions (hot-dipped zinc, galvanneal, back contact of thin film photovoltaic solar cells and tinplates).

Quantitative depth profile analysis of boron implanted silicon by pulsed radiofrequency glow discharge time-of-flight mass spectrometry

The analytical potential of pulsed radiofrequency glow discharge time-of-flight mass spectrometry (pulsed-rf-GD-TOFMS) is investigated for fast quantitative analysis of major and dopant elements in bulk and thin film layers. This technique does not require sampling at ultra-high vacuum conditions and so it facilitates high sample throughput compared to reference techniques as secondary ionization mass spectrometry (SIMS). In this paper, bulk and boron implanted silicon samples are analyzed. Boron concentration in Si samples is calculated from calibration curves obtained using solar grade silicon and B doped silicon wafers as calibrating materials, and using 29Si + ion signal as internal standard. Qualitative depth profiles of 10B implanted silicon are determined in a few seconds using the low-pressure pulsed-rf-GD-TOFMS system. Additionally, quantitative depth profiles are easily determined making use of the calibration curves. A good agreement with the depth profiles measured using SIMS was obtained, demonstrating the analytical potential of the pulsed-GD-TOFMS system for fast, sensitive and high depth resolution analysis of implanted silicon samples.

The hydrogen effect as a function of discharge parameters - investigations of the variation of emission yield in glow discharge plasmas

It is well known that traces of hydrogen in the glow discharge plasma enhance or suppress the intensities of other spectral lines, in this work termed “the hydrogen effect”. In this work, the focus is on the variation of the hydrogen effect as a function of the discharge parameters, for the purpose of developing effective correction methods in quantitative depth profile analysis. A simple, but effective experimental method was employed: The intrinsic contamination of the source leads to an increased amount of hydrogen in the plasma at the beginning of the discharge, which is rapidly reduced with sputtering time. Thus, by recording the intensity depth profiles of multi-element bulk reference materials, the influence of hydrogen on several emission lines can be observed. The decay or increase in intensity, correlated to the intensity of the hydrogen emission line, gives the desired information. Systematic investigations by varying current and voltage in a considerable range provided a good matrix of data to find a model describing these variations. Furthermore, renewed investigations of the variation of emission yields (EY) with discharge parameters have led to a model which has been used to correct the obtained data for the hydrogen intensities, so as to represent the actual content of hydrogen in the plasma. The information extracted from these studies is expected to be of great importance for routine depth profile analysis, as the hydrogen correction is a relevant tool in software quantification algorithms. Existing correction models for the hydrogen effect do not take variations in the discharge parameters into account. This work clearly shows that it is necessary to implement such variations for accurate correction.

SIMS and GDMS depth profile analysis of hard coatings

Rapid development in hard coating technology calls for simple construction depth profile analysers. Here we present results of depth profile analysis of a set of Ar arc plasma deposited TiN, CrN layers. The results are obtained with the use of recently constructed simple glow discharge mass spectrometer (GDMS) and compared with secondary ion mass spectrometer (SIMS). In SIMS (SAJW-05 model) we apply 5 keV Ar + ion beam of about 100 μm in diameter. Digitally controlled spiral scanning of primary ion beam is performed over 1.6 mm 2 area. Secondary ions are extracted from the central part due to an “electronic gate” and analysed by quadrupole mass spectrometer QMA-410 Balzers (16 mm rods). GDMS analyses are performed on SMWJ-01 glow discharge prototype spectrometer. To supply discharge in 1 hPa argon we use 1.5 kV DC voltage. The analysed sample works as a cathode in a discharge cell. Area of the analysis is ∼4 mm 2 due to the use of secondary cathode—high purity tantalum diaphragm. Sputtered atoms are ionised, next extracted into the analytical chamber and finally analysed by the quadrupole mass analyser SRS-200 (6 mm rods). The results show that the use of simple construction GDMS analyser allows obtaining similar or even slightly better depth resolution than it can be obtained in the SIMS spectrometer. Application of glow discharge analysis opens new possibilities in direct quantitative depth profile analysis of hard coatings.