Secondary Ion Mass Spectrometry Quantification Research Articles

Quantification of secondary ion mass spectrometry measurements by using ion‐implanted metallic standards

This research addresses an analytical methodology to quantify elements of interest in fusion‐relevant materials using secondary ion mass spectrometry (SIMS). For this purpose, internal standards have been fabricated by ion implantation to avoid the well‐known matrix effect of this technique. In particular, chromium has been implanted at an energy of 12 MeV using two fluences in high‐purity iron and tungsten matrices together with Si control substrates. The latter were applied to determine the Cr concentration implanted through experimental and semiempirical methods. Specifically, the IBA technique Rutherford backscattering spectrometry (RBS) provided the quantitative results being 3.1 × 1019 at/cm3 and 1.6 × 1019 at/cm3 for the high and low dose, respectively. The SIMS depth profiles of Cr for the Fe and W matrices established an ion implantation depth close to 2 μm on both substrates in agreement with the calculations previously performed by Stopping and Range of Ions in Matter (SRIM) simulations. Correlation between the integration of SIMS profiles and known concentrations of the implanted ion resulted in the calibration curve for each matrix, obtaining the SIMS quantification approach by means of this relative sensitivity factor (RSF). Additionally, a cross‐check of the method by comparing commercial Fe‐Cr alloys with the Cr‐implanted Fe matrices of the present study pointed out the need to produce standards with higher chromium concentrations.

Erratum: “Secondary ion mass spectrometry quantification: Do you remember when a factor of 2 was good enough?” [J. Vac. Sci. Technol. B 41, 030803 (2023)

Erratum: “Secondary ion mass spectrometry quantification: Do you remember when a factor of 2 was good enough?” [J. Vac. Sci. Technol. B 41, 030803 (2023)

Secondary ion mass spectrometry quantification: Do you remember when a factor of 2 was good enough?

Well, do you remember when a factor of 2 was good enough? Probably, not unless you have been around secondary ion mass spectrometry (SIMS) since the early 1960s, like one of us has been. This paper will give many references back to the early days of quantification when a local thermal equilibrium model was used to obtain the first results that were accurate to within a factor of 2, but only 60% of the time. It only worked for bulk silicate matrixes. People were not even using SIMS on semiconductors in those days. Several early references showing profiles of ion implants in Si will be referenced, but it was not until 1980 that the first paper was published that explicitly showed how to use ion implants as SIMS standards. People were using ion implants as standards before 1980, but only in limited cases, and with no formal published equations specifying how to use them. But, the samples for which ion implants were used as standards were for dilute concentrations in a single matrix, which had a uniform matrix composition with depth. The rest of the paper will show how we at Eurofins EAG Laboratories tackled the problem of quantification of both major and minor elements in nonuniform, multi-element matrices with continuously graded composition changes using point-by-point CORrected-SIMS. These include SiGe heterostructure bipolar transistors, AlGaAs vertical cavity surface emitting lasers, and B plasma-implanted poly-silicon gates.

Secondary ion mass spectrometry quantification of boron distribution in an array of silicon nanowires

The development of non-planar structures such as arrays of nanowires (NWs), poses a significant challenge for dopant concentration determination. Techniques that can be readily used for 3D structures usually lack the desired sensitivity whereas secondary ion mass spectrometry (SIMS), known for its excellent detection limits, is designed to analyze flat samples. In this work, we overcome the limitation of standard SIMS approaches. NWs are covered with photoresist forming a flat surface. For high incident angle bombardment, the sputtering process becomes self-flattening, i.e. the ions collide with the sidewalls of the exposed tips of NWs at much lower angles and sputter them significantly faster. Thus, reliable information about the dopant distribution along the height of NWs can be obtained. The SIMS analysis can be performed on an array of 1000 x 1000 nanowires with a detection limit of about 5 x 1016 atoms/cm3 and a reasonable signal-to-noise ratio of about 10 dB.

A two‐point calibration method for quantifying organic binary mixtures using secondary ion mass spectrometry in the presence of matrix effects

Quantification of the composition of binary mixtures in secondary ion mass spectrometry (SIMS) is required in the analyses of technological materials from organic electronics to drug delivery systems. In some instances, it is found that there is a linear dependence between the composition, expressed as a ratio of component volumes, and the secondary ion intensities, expressed as a ratio of intensities of ions from each component. However, this ideal relationship fails in the presence of matrix effects and linearity is observed only over small compositional ranges, particularly in the dilute limits. In this paper, we assess an empirical method, which introduces a power law dependence between the intensity ratio and the volume fraction ratio. A previously published physical model of the organic matrix effect is employed to test the limits of the method and a mixed system of 3,3′‐bis(9‐carbazolyl) biphenyl and tris(2‐phenylpyridinato)iridium (III) is used to demonstrate the method. This paper introduces a two‐point calibration, which determines both the exponent in the power law and the sensitivity factor for the conversion of ion intensity ratio into volume fraction ratio. We demonstrate that this provides significantly improved accuracy, compared with a one‐point calibration, over a wide compositional range in SIMS quantification and with a weak dependence on matrix effects. Because the method enables the use of clearly identifiable secondary ions for quantitative purposes and mitigates commonly observed matrix effects in organic materials, the two‐point calibration method could be of significant benefit to SIMS analysts.

Calibration correction of ultra low energy SIMS profiles based on MEIS analyses for arsenic shallow implants in silicon

Secondary ion mass spectrometry (SIMS) and medium energy ion scattering (MEIS) have been applied to the characterization of ultra shallow distribution of arsenic in silicon obtained by ion implantation at 0.5–5 keV. MEIS offers the advantage of accurate quantification and ultimate depth resolution <1 nm but the detection limit achievable is always poorer than the one obtained by SIMS. The comparison of the results obtained by the two techniques allows to discriminate among different SIMS quantification processes in order to individuate the best in terms of accuracy in the initial transient width and at the SiO 2–silicon interface and develop quantitative model for SIMS profiles to align them to the curves as determined by MEIS. This model relies on different sputtering condition in SiO 2 (such as sputtering rate and ion yield) and additionally compensates analysis behavior in SiO 2/Si interface.

Strategies for Quantification of Light Elements in Minerals by SIMS: H, B and F

Using a large set of silicate crystals, characterized by Structure REFinement (SREF), Electron Probe Micro-Analysis (EPMA) and Secondary Ion Mass Spectrometry (SIMS), and mounted with known crystallographic orientation [1], we propose a new SIMS quantification for H, B and F (from ppm level to several wt.%), using 27Al+ and 44Ca+, in turn, as the reference isotope for the matrix, and propose suitable calibration standards to obtain accurate results. The final SIMS data are then compared to those obtained using Si as the reference element, with those available from EMPA (B and F), and with the crystallographic constraints derived from SREF investigation. The results of this study can be extended to the measurement of light elements in complex silicate or non-silicate samples.

Characterization of Amorphous Silicon by Secondary Ion Mass Spectrometry

AbstractBased on various implanted standards, we have used SIMS (Secondary Ion Mass Spectrometry) to characterize amorphous Si thin films with high hydrogen content. SIMS and HFS (Hydrogen Forward Scattering) showed good agreement on the measured total H doses for H-implanted Si samples and the a-Si thin films. For the H-implanted Si samples, in the dose range of 2e15 atoms/cm2 to 2e17 atoms/cm2 (corresponding to peak H concentration from 0.32 at.% to 32 at.%), SIMS results showed that the calibration curve is a straight line. In other words, no correction for SIMS quantification is needed when moving from low to high hydrogen content samples. Analysis of P (Phosphorus) in a-Si thin films requires the use of high mass resolution magnetic sector SIMS to separate P and a mass interference from (30Si+H). Using a magnetic sector SIMS instrument, P-doped a-Si thin layers (˜ 50nm thick) were analyzed using 3keV O2 beam with oxygen leak for better depth resolution and improved detection limits. For the analysis of C, N, O in a-Si thin films (again approximately 50nm thick) the profiling energy typically needs to be lowered down to 3keV and the material needs to be sputtered at a high rate in order to reach real background levels. In this work, a-Si thin films were also analyzed using a 3keV Cs+ primary ion beam with (Cs2M)+ (M= C, N, O) detection for good depth resolution and detection limits.

Effect of CdCl 2 activation on the impurity distribution in CdTe/CdS solar cell structures

CdTe/CdS/In 2O 3:F/glass solar cell structures made using 7N CdTe were investigated to determine the distribution of impurities. This study was carried out using quantitative secondary ion mass spectrometry (SIMS) profiling from the CdTe surface through the glass substrate. Particular emphasis was placed on the potential for electrically active impurities to originate from the cadmium chloride (CdCl 2) processing step, since such impurities are likely to affect the CdTe/CdS device performance. The impurities: Cl, O, Cu, Na, In, Sb, Sn, Si, Zn, Pb and S were profiled for as-grown and CdCl 2 treated structures. Ion implanted CdTe and CdS standards were used for SIMS quantification. It has been shown that O and Cu do not originate from the CdCl 2 activation process. Zn, Sn and Pb are also invariant on processing. Other impurities such as Cl, Na and Sb are definitely present in the activated structures due to their presence in the CdCl 2 starting material used in the treatment. Si diffusion from the glass substrate as well as Te and S interdiffusion at the CdTe/CdS interface following the CdCl 2 treatment were also highlighted.

SIMS: a capable method for BCN quantification

Obvious matrix effects often inhibit major component analysis carried out with secondary ion mass spectrometry (SIMS). Although MCs + secondary ions (M represents the element to be analyzed) are used — already know as matrix independent for some compounds — feasibility of SIMS quantification has separately be validated for each new system. For the ternary system consisting of boron, carbon and nitrogen (BCN), all features possibly influences quantification, i.e. uniqueness of detected secondary ion signals, charge effects, altering measurement conditions, reproducibility or matrix effects are investigated and taken into account. The results indicate that an accurate quantification applying SIMS for major component analysis is possible for this system. Furthermore, deviations between SIMS results and real compositions are determined.

SIMS quantification of As and In in Hg1−xCdxTe materials of different x values

This paper presents a study of Secondary Ion Mass Spectrometry (SIMS) quantification of As and In in Hg1–xCdxTe materials. The SIMS results show that for Hg1-xCdxTe with x from 0.2 to 0.8, As and In quantification is independent of the x-values (0.2–0.8). The relative sensitivity factors (RSF) for In and As derived from the standard of one x value can be used to accurately quantify unknown samples of different x value(s). We also determined the dependence of sputtering rate vs. x values under oxygen beam bombardment.

SIMS and RBS analysis of leached glass: Reliability of RSF method for SIMS quantification

The reliability of the relative sensitivity factor (RSF) approach for secondary ion mass spectrometry (SIMS) quantification of the leached layers on glass was investigated by measuring comparable samples of glass with SIMS and RBS (Rutherford backscattering spectrometry). The RSF factors were calculated using the nominal bulk compositions. Accurate results can be obtained only when the leached layer and the bulk glass have the same major elemental compositions (Si and O) and the matrix effect is inhibited. The concentrations of the different elements in the leached layer obtained from the comparable samples measured by SIMS and RBS are coincident within a factor of 2

Evaluation of matrix effects in SIMS quantification of Al xGa 1−xAs/GaAs heterostructures: a SNMS approach

Al x Ga 1− x As/GaAs heterostructures (0.15 ≤ x ≤ 0.4) have been studied using Secondary Ion Mass Spectrometry (SIMS) and Sputtered Neutral Mass Spectrometry (SNMS) techniques. A thin MQW structure was also investigated. Both techniques give a good quantification of the constituent elements in these systems, provided that standard samples are available. It is shown that SNMS provides a tool for quantitative evaluation of the matrix effect in SIMS measurements. In addition, a standardless method for the determination of the Ga content in Al x Ga 1− x As/GaAs heterostructures by means of SNMS is proposed.

Secondary ion mass spectrometry quantification of elements in TiSi2, TiN, and TiW matrices

The titanium based matrices TiSi2, TiN, and TiW are used extensively in current semiconductor fabrication. Quantification of elements in these matrices using secondary ion mass spectrometry (SIMS) is hampered by a lack of available information on the relative secondary ion yields for the elements of interest and by a large number of mass interferences. This study provides the ion yields in the form of relative sensitivity factors (RSFs) for a large number of elements ion implanted into these three matrices and describes methods of analysis to circumvent mass interferences of important elements. The RSFs can be organized into patterns of positive secondary ion RSFs versus ionization potential and negative secondary ion RSFs versus electron affinity, similar to those measured for other matrices. The use of molecular ions can improve detection limits for some elements with mass interferences that are beyond the mass resolution capabilities of many SIMS instruments. Depth resolution in TiW is adversely affected by surface roughening during ion bombardment.

Depth profiling and secondary ion mass spectrometry relative sensitivity factors and systematics for polymers/organics

Depth profiles and secondary ion mass spectrometry (SIMS) relative sensitivity factors (RSF) for quantification (inverse relative ion yields) are reported for oxygen ion bombardment and positive secondary ion mass spectrometry and for cesium bombardment and negative secondary ion mass spectrometry measured for implants of more than 40 elements in PMMA/polymethyl methacrylate/Lucite/AZ111, polypyromellitimide/polyimide/Kapton, and epoxy, using magnetic sector SIMS instruments (CAMECA IMS 3f or 4f). The RSFs are plotted versus ionization potential (positive secondary ions) and versus electron affinity (negative secondary ions), and the resulting patterns are compared among themselves and with those for semiconductors reported previously. Charge compensation using electron flooding was employed in most cases for both oxygen (oblique incidence flooding) and cesium (normal incidence flooding) primary beams. Profiles in these low atomic number materials are relatively deep. Crater depths are sometimes difficult to measure; some are distorted and some are not. More work in this area of SIMS quantification and depth profiling in organic polymers appears to be needed, but these results are promising.

Secondary ion mass spectrometry quantification of Be in AlxGa1−xAs/GaAs multilayer structures

The 84AsBe− molecular ions under Cs+ bombardment were used to detect Be atoms in AlGaAs/GaAs heterostructures. They showed a negligible matrix dependence, compared to that of the 9Be+ ions under O+2 bombardment. The suppressed matrix effect in the former case provided a more straightforward and accurate way for secondary ion mass spectrometry quantification.