Magnetic Sector SIMS Research Articles

Accurate determination of matrix composition in Cd x Zn 1 − x O semiconductor material using MS-SIMS and ToF-SIMS methods

Abstract This study focuses on the method for determining the exact composition for Cd x Zn 1 − x O semiconducting material using secondary ion mass spectrometry. The calibration curve method is employed to establish a quantitative relationship between the intensity of secondary ions and the concentrations of elements in Cd x Zn 1 − x O thin films. Additionally, the study compares the relative sensitivity factors with the calibration curve method for determining the value of x in Cd x Zn 1 − x O . A comparison between the performances of Time of Flight and Magnetic Sector SIMS in analyzing Cd x Zn 1 − x O thin films is also presented. This approach aims to enhance the accuracy and reliability of quantitative analysis in SIMS for Cd x Zn 1 − x O thin films.

Determining the oxygen detection limit with magnetic sector dynamic secondary ion mass spectrometry (SIMS)

Dynamic SIMS is often used in evaluating the concentration of impurities in solids because of its high sensitivity and depth profiling capabilities with good depth resolution and high throughput. Continuous ion beam sputtering with a high-density primary beam provides high sensitivity and reduced background contribution from residual gases within the analytical chamber. Numerical simulations along with the data acquired in the real depth profiling experiment show a good agreement of the simple model, assuming that the surface uptake of the oxygen under Cs bombardment depends on the Cs surface retention concentration. In cases where high depth resolution is desired, requiring a low primary ion beam energy, a background subtraction option will help provide better detection limits. It is proposed to perform the background subtraction based on the difference between the continuous and interleaving sputtering modes of dynamic SIMS. The experiments performed on different instruments using different sputtering rate conditions (and different impact energies) show the power function dependence of oxygen detection limit on the reversed sputter rate variation or sputtering beam density. The proposed detection limit dependence curve can be used for analytical specifications benchmarking in most magnetic sector SIMS instruments.

Magnetic Sector SIMS System with Continuous Focal Plane Detector for Advanced Analytical Capabilities on FIB Instruments

Journal Article Magnetic Sector SIMS System with Continuous Focal Plane Detector for Advanced Analytical Capabilities on FIB Instruments Get access Tom Wirtz, Tom Wirtz Luxembourg Institute of Science and Technology (LIST), Belvaux, Grevenmacher, Luxembourg Search for other works by this author on: Oxford Academic Google Scholar Olivier De Castro, Olivier De Castro Luxembourg Institute of Science and Technology (LIST), Belvaux, Grevenmacher, Luxembourg Search for other works by this author on: Oxford Academic Google Scholar Antje Biesemeier, Antje Biesemeier Luxembourg Institute of Science and Technology (LIST), Belvaux, Grevenmacher, Luxembourg Search for other works by this author on: Oxford Academic Google Scholar Hung Quang Hoang, Hung Quang Hoang Luxembourg Institute of Science and Technology (LIST), Belvaux, Grevenmacher, Luxembourg Search for other works by this author on: Oxford Academic Google Scholar Jean-Nicolas Audinot Jean-Nicolas Audinot Luxembourg Institute of Science and Technology (LIST), Belvaux, Grevenmacher, Luxembourg Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 26, Issue S2, 1 August 2020, Pages 1972–1974, https://doi.org/10.1017/S1431927620019984 Published: 01 August 2020

Comparison of quantitative analyses using SIMS, atom probe tomography, and femtosecond laser ablation inductively coupled plasma mass spectrometry with Si1−XGeX and Fe1−X NiX binary alloys

Due to their electrical and physical properties, Si1−XGeX materials are widely used in microelectronic devices. In particular, the Ge component found within Si1−XGeX compounds is important for enhancing carrier mobility and altering the lattice constant of metal-oxide-semiconductor field-effect transistors. In this study, magnetic sector secondary ion mass spectrometry (magnetic sector SIMS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to determine the accurate concentrations of major compositions present within binary alloy samples. However, quantitative SIMS analysis is limited by the matrix effect, which influences the sputter yield of an element in a compound and alters the secondary ionization yields. Quantitative deviations that were due to the matrix effect were reduced by using Cs cluster ions (MCs+ and MCs2+) instead of elemental ions; the SIMS results using the elements were, therefore, compared with those using MCs+ and MCs2+ cluster ions. In the case of Fe1−XNiX alloys that have a less matrix effect compared to Si1−XGeX alloys, both the Cs primary ion beam (Cs+) and an oxygen primary ion beam (O2+) were used to measure the Fe1−XNiX compositions. The quantitative results from the two different primary ion beams were then compared to understand the ionization process. Deviations in the quantitative values gained with the O2+ beam were lower than those obtained using the Cs+ primary ions, meaning that using oxygen as the primary ion improves the accuracy in quantifying Fe1−XNiX compounds. Other reliable tools for analysis such as atom probe tomography and femtosecond laser ablation inductively coupled plasma mass spectrometry were also used in the quantitative analysis, with results that were consistent with the most accurate results obtained using magnetic sector SIMS and ToF-SIMS.

Stability of Zircon and Its Isotopic Ratios in High-Temperature Fluids: Long-Term (4 months) Isotope Exchange Experiment at 850°C and 50 MPa

Stability of zircon in hydrothermal fluids and vanishingly slow rates of diffusion identify zircon as a reliable recorder of its formation conditions in recent and ancient rocks. Debate, however, persists on how rapidly oxygen and key trace elements (e.g., Li, B, Pb) diffuse when zircon is exposed to hot aqueous fluids. Here, we report results of a nano- to micrometer-scale investigation of isotopic exchange using natural zircon from Mesa Falls Tuff (Yellowstone) treated with quartz-saturated, isotopically (18O, D, 7Li, and 11B) labeled water with a nominal δ18O value of +450‰ over 4 months at 850°C and 50 MPa. Frontside (crystal rim inwards) δ18O depth profiling of zircon by magnetic sector SIMS shows initially high but decreasing 18O/16O over a ~130 nm non-Fickian profile, with a decay length comparable to the signal from surficial Au coating deposited onto zircon. In contrast, backside (crystal interior outwards) depth profiling on a 2-3 µm thick wafer cut and thinned from treated zircon by focused ion beam (FIB) milling lacks any significant increase in 18O/16O during penetration of the original surface layer. Near-surface time-of-flight (TOF-SIMS) frontside profiles of uncoated zircon from 4-month and 1-day-long experiments as well as untreated zircons display similar enrichments of 18O over a distance of ~20 nm. All frontside 18O profiles are here interpreted as transient surface signals from nm-thick surface enrichment or contamination unrelated to diffusion. Likewise, frontside depth profiling of H, Li, and B isotopes are similar for long- and short-duration experiments. Additionally, surface U-Pb dating of zircon from the 4-month experiment returned U-Pb ages by depth profiling with ~1 µm penetration that were identical to untreated samples. Frontside and backside depth-profiling thus demonstrate that diffusive 18O enrichment in the presence of H2O is much slower than predicted from experiments in Watson and Cherniak (1997). Instead, intracrystalline exchange of oxygen between fluid and zircon in wet experimental conditions with excess silica occurred over length-scales equivalent to those predicted for dry diffusion. Oxygen diffusion coefficients even under wet conditions and elevated temperatures (850 °C) are <1-3×10-23 m2/sec, underscoring a virtual lack of oxygen diffusion and an outstanding survivability of zircons

Detection of Matrix Elements and Trace Impurities in Cu(In, Ga)Se2 Photovoltaic Absorbers Using Surface Analytical Techniques.

Chalcopyrite Cu(In, Ga)Se2 (CIGS) thin films are well known as the next-generation solar cell materials notable for their high absorption coefficient for solar radiation, suitable band gap, and ability for deposition on flexible substrate materials, allowing the production of highly flexible and lightweight solar panels. To improve solar cell performances, a quantitative and depth-resolved elemental analysis of photovoltaic thin films is much needed. In this study, Cu(In, Ga)Se2 thin films were prepared on molybdenum back contacts deposited on soda-lime glass substrates via three-stage evaporation. Surface analyses via AES and SIMS were used to characterize the CIGS thin films and compare their depth profiles. We determined the average concentration of the matrix elements, Cu, In, Ga, and Se, using ICP-AES, XRF, and EPMA. We also obtained depth profiling results using TOF-SIMS, magnetic sector SIMS and AES, and APT, a sub-nanometer resolution characterization technique that enables three-dimensional elemental mapping. The SIMS technique, with its high detection limit and ability to obtain the profiles of elements in parallel, is a powerful tool for monitoring trace elements in CIGS thin films. To identify impurities in a CIGS layer, the distribution of trace elements was also observed according to depth by SIMS and APT.

Quantitative analysis for CIGS thin films by surface analytical techniques

The compound semiconductor Cu(In,Ga)Se2 (CIGS) is well known as the next‐generation solar cell material because of its high absorption coefficient for solar radiation, suitable band gap, ability to be deposited on flexible substrate materials, and producing highly flexible and lightweight solar panels. In order to improve the performance of solar cells, a quantitative and depth‐resolved elemental analysis of photovoltaic thin films is strongly required. In this study, we determined the average concentration of the major elements, Cu, In, Ga, and Se in fabricated CIGS thin films, using inductively coupled plasma atomic emission spectrometry, X‐ray fluorescence, and electron probe microanalysis. Depth profiling results for CIGS samples using AES, XPS, magnetic sector SIMS, and time of flight SIMS were also obtained to compare their atomic concentration results. In the SIMS technique, detection of MCs+ clusters reduced possible matrix effects because of the variant concentrations of In and Ga. The reproducibility and accuracy of quantitative analysis were investigated as a function of ion sputtering energy. The compositional distributions of CIGS absorber layers as measured by MCs+–SIMS showed good agreement with those of AES and XPS. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Optimizing charge neutralization for a magnetic sector SIMS instrument in negative mode

Successful self-adjusted charge compensation was demonstrated for a CAMECA magnetic-sector secondary ion mass spectrometer applied in negative mode. Operation with the normal-incidence electron gun (NEG) potential positively biased relative to a sample potential enables substantial broadening of the Cs primary-ion-current density range available for analysis of insulators. The decrease of the negative NEG potential by 30 V allows the highest value of primary current density used for the analysis of a silica sample to increase by a factor of more than 6. By applying the improved charge neutralization technique, accurate Na depth profiles for SiO2 samples were obtained within detection limits of ∼3 × 1015 atoms/cm3.

Suppressing the redistribution of boron in crystalline silicon during SIMS analysis

AbstractBoron is one of the most commonly used p‐type dopant in silicon. We found that boron in crystalline silicon does not have identical distribution in depth profile between front side and rear side SIMS analysis. Comparing boron profiles of both analyses, different distributions can be seen at the depth in a few hundreds of nanometers from the surface side. Additionally, we continued analysis to investigate the behavior of boron in homogenously boron‐doped sample, such as p‐type silicon substrate. The result showed that distortion arises at the surface side during analysis and consequently nonuniform distribution was obtained. From the results, we estimate that boron should be redistributed during usual SIMS analysis, and study various analytical conditions in order to suppress such phenomenon. In this study, entire experiments were carried out by CAMECA ims 6f and 7f instruments, known as magnetic sector SIMS. Several ion‐implanted samples having different conditions are prepared for the analyses.As a result of experiments, redistribution of boron in crystalline silicon is suppressed suitably by cooling method using liquid nitrogen. Furthermore, it was revealed that the boron redistribution takes place in activation‐annealing samples, while the redistribution cannot be observed in as‐implanted samples. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Numerical approach to resolve mass interference in depth profiling As in SiGe

AbstractSIMS analysis of SiGe material is intricate and challenging due to the mass interference effects. For instance, analysis of arsenic (As) in SiGe requires ultra‐high mass resolution (MR) to resolve the mass interferences to As and AsSi. Unfortunately, the ultra‐high MR is achieved at the cost of sensitivity for magnetic sector SIMS. Especially in the case of low‐dose As implantation, 75As28Si− should be monitored to ensure enough dynamic range. But the required MR to resolve mass interference of 74Ge29Si− to 75As28Si− is too high for all types of SIMS systems. In this work, a numerical approach has been developed to eliminate the mass interference to AsSi based on the dependence of interference ion intensity on Ge concentration. An undoped SiGe sample with a Ge fraction of 0.128 was used as the reference sample to determine the dependence of interference ion intensity on Ge‐contained reference ions intensity. Interpolation algorithm was applied to minimize the deviation caused by the test time difference. The effectiveness of two interpolation algorithms, linear and exponential interpolation, was evaluated in this paper. Gaussian‐like profiles of As implantation with the dose of 3.6E13 at/cm2 and 1E15 at/cm2 were obtained with this numerical approach. The profile of 1E15 at/cm2 As implantation agreed quite well with that obtained with ultra‐high mass resolution, and achieved at least two orders of improvement in the dynamic range. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Back side SIMS analysis of hafnium silicate

High-k dielectrics are under study as part of the effort to continually reduce semiconductor device dimensions and hafnium silicate (HfSi x O y ) is one of the most promising high-k materials. A requirement of the dielectric is that the constituent elements cannot diffuse into adjacent device regions during thermal processing. Analysis for inter-diffusion using front side SIMS of high-k dielectrics has been complicated by matrix and sputtering effects. Use of a back side analysis sample preparation procedure that was successful for copper diffusion and site specific studies produced a HfSiO specimen that has less than 250 nm silicon remaining and minimal slope over the analysis region. Magnetic Sector (CAMECA IMS-6F) SIMS analysis of this specimen with low energy O 2 + bombardment does not show the matrix and sputtering effects noted in the front side data. Sufficient depth resolution was obtained to define the interface between the silicon substrate and the HfSiO layer and indicate what appears to be an interfacial layer. There is no indication of hafnium diffusion into the silicon substrate.

Improved charge neutralization method for depth profiling of bulk insulators using O 2+ primary beam on a magnetic sector SIMS instrument

Use of electrons for charge neutralization during positive secondary ion SIMS analysis of insulators has typically been achieved using coincident primary ion and electron beams. The normal incidence electron gun on CAMECA magnetic sector SIMS instruments can effectively eliminate sample charging during analysis of thin insulating films if the electron energy is sufficient to penetrate the film. However, positive secondary ion SIMS bulk insulator analysis using this instrument can be difficult, especially if high sputtering rates are required. A neutralization method has been developed utilizing electron beam impact of a region adjacent to the sputtered area. Prior to analysis, the surface of the sample is coated with gold which provides a conductive surface layer and which has a high secondary and backscattered electron yield. Results have been obtained showing excellent neutralization for a variety of bulk insulators including glass, silica, alumina, and lithium niobate. Sputtering rates exceeding 2 nm/s have been achieved in bulk silica. The technique should be applicable to minerals and possibly for other materials in cases where the analyzed area cannot be directly irradiated with an electron beam.

Utilization of electron impact ionization of gaseous and sputtered species in the secondary ion acceleration region of a magnetic sector SIMS instrument

Negative secondary ion insulator analysis using a normal incidence electron gun (NEG) on CAMECA magnetic sector SIMS instruments can be difficult due to an inability to adequately determine the electron beam impact region during NEG alignment. The electron impact energy is too low to utilize phosphor cathodoluminescent materials that can be used for NEG alignment for positive secondary ion analyses. Detection of electron beam desorbed H − is often used for NEG alignment, but the presence of H on the surface is not always uniform and it is transient, making it difficult to determine whether variations in the H − secondary ion intensity are due to non-uniformity of the electron beam or of the H on the sample. To overcome this difficulty, a new technique has been developed that takes advantage of sputtering of the sample surface by positive ions created by electron impact ionization in the spectrometer secondary ion acceleration region between the sample and the immersion lens of the mass spectrometer. The formation of the ions occurs by interaction of residual gas species in the spectrometer secondary ion acceleration region with the NEG electron beam. This method is used to align the NEG for negative secondary ion charge neutralization.

Short-term and long-term RSF repeatability for CAMECA SC-Ultra SIMS measurements

The higher degree of instrumental automation becomes increasingly important in order to reduce the operator attendance for SIMS analyses. Concurrently a high repeatability is demanded from these instruments to guarantee process reproducibility or material uniformity. This work is focused on the depth profiling repeatability obtained from the new magnetic sector SIMS instrument CAMECA SC-Ultra 300 for arsenic, boron and phosphorous implants in silicon. The short-term repeatability has been evaluated by performing a continuous sequence of automatic measurements: RSF repeatability better than 1% has been obtained over a single day. Additionally the long-term repeatability has been evaluated by repeating several weeks later the same measurements with the instrumental presets stored by software, i.e. without changes in the analytical parameters. The RSF repeatability values are about 3% for As with cesium source and 5% for B with oxygen primary beam.

The features of using of BO 2− secondary ions for SIMS depth profiling of shallow boron implantation in silicon

The strong influence of oxygen to the positive secondary ion yield determines the problems of SIMS depth profiling of shallow boron implants in silicon, related to surface oxide and formation of modified layer. High value (4 eV) of electron affinity of BO 2 molecule responds for the high yield of BO 2 − negative secondary ions, its small sensitivity to the variation of emission properties of the sample surface and relatively weak dependence on oxygen concentration. The features of using of named ions for shallow boron profiling was studied with a magnetic sector SIMS instrument in a high mass resolution mode under O 2 − and NO 2 − primary ion bombardment. The refuse from oxygen flooding allowed to avoid the initial significant change of sputter rate. The studied approach provides simplification of transient phenomena while still keeping sufficient sensitivity.

Ultrashallow profiling of semiconductors by secondary ion mass spectrometry:: methods and applications

We have investigated in detail the capability of a CAMECA IMS-4f magnetic-sector SIMS instrument in terms of ultimate depth resolution, accuracy, quantification in the uppermost layers, sensitivity and dynamic range, as well as fastness and ease of measurement. A method to obtain ultrahigh depth resolutions will be demonstrated and discussed. The study has primarily been finalized to the investigation of ultrashallow boron implants in silicon. Specific applications to the above-mentioned material will be presented. In particular, it will be shown that, taking advantage of the developed measurement protocol, it was possible to perform a detailed investigation on the atomic transport properties of the sub-keV energy implanted boron in silicon.

Recent instrumental developments in magnetic sector SIMS

The recent developments in magnetic sector SIMS are reviewed. It is not aimed at a detailed description of these instruments which, for several of them, can be found elsewhere [1–8] but reviews the driving forces making necessary the development of magnetic sector SIMS for all types of analysis (single instrument alternative) as well as instruments dedicated to ultimate lateral resolution (50 nm), to isotopic ratio measurements with multicollection of all isotopes, to depth profiling at high depth resolution using an impact energy of 250 eV, and instruments allowing better flexibility about the amount of cesium incorporated in the specimen to optimize the formation of MCs clusters for the analysis of complex materials.

Isotopic Measurements of Inorganic Material by Time-Of-Flight SIMS

Abstract Isotopic measurements via Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) have generally not been considered as practical because of the low duty cycle at which ToF-SIMS instruments operate and the corresponding low data rate. The recent discovery of pre-solar material in meteorites has shown that large variations in isotopic ratios (several orders of magnitude for some elements) exist in small (∼1 μm), refractory meteoritic grains. These grains are ideal candidates for ToF-SIMS, which consumes little sample material, compared to dynamic, magneticsector SIMS. ToF-SIMS also allows for parallel detection of all species present in the sample; thus, multiple isotopic systems can be studied in one measurement. As a prerequisite to studying the isotopic composition of meteoritic materials, preliminary determinations of ratios for a number of elements have been made on materials of known isotopic composition. This allows us to investigate problems that may be unique to ToF-SIMS for the measurement of isotopic ratios.

A Novel Approach for the Determination of the Actual Incidence Angle in a Magnetic-sector SIMS Instrument

A novel approach for the determination of the incidence angle in a magnetic-sector SIMS instrument is described. It is based on accurate mapping of the primary beam in the extraction field near the sample surface. The accuracy of the method and the applicability of simple formulas are discussed in detail. In addition, the variation in the incidence angle over the rastered area has been measured and it is shown that, by adjusting the potential on the extraction electrode, this angle can be selected. Grazingly incident primary beams with energies well below 1 keV have been produced. © 1997 by John Wiley & Sons, Ltd.

Profiling Shallow As Implants with Low‐energy Cs Bombardment on a Modified Cameca IMS-4f

The inability to decouple primary ion beam energy and incidence angle in Cameca-type magnetic sector SIMS instruments makes profiling shallow As implants (⩽20 keV), using typical Cs+ bombardment conditions and negative secondary ion detection, problematic. A Cameca IMS-4f has been modified to lower the Cs+ primary beam impact energy by concomitant decreases in primary ion beam energy and sample potential. Evaluation of the instrument's performance after modification shows about a 35% improvement in depth resolution as defined by the decay length, λ, of a 20 keV As implant profile. This is accompanied by a decrease in useful yield, resulting from the lower sample potential, of about a factor of eight. Comparison of Cameca IMS-4f data from a 5 keV As implant with data obtained on a quadrupole-based instrument suggests that the Cameca's fixed incidence angle at low energy is the limiting factor to further improvements in depth resolution. Nevertheless, the ease and relatively low cost of modification makes this an attractive approach to increasing the range and flexibility of existing Cameca SIMS instruments. © 1997 John Wiley & Sons, Ltd.