Cameca IMS-3f Research Articles

SIMS depth profiling and direct ion imaging of a 16-megabit DRAM

The use of secondary ion mass spectrometry (SIMS) has long been established as a powerful tool forthe analysis of microelectronic devices. However, as newer fabrication technologies emerge, and device dimensions shrink, increasing demands are placed upon the SIMS analyst.The present work illustrates how the depth profiling and direct ion imaging capabilities of a Cameca ims 4f SIMS can be exploited to determine the structure and dopant chemistry of a state-of-the-art16 megabit DRAM (dynamic random access memory) device. The optical micrograph shown in Fig. 1 is an overview of a portion of the sense amplifiers located between two array blocks. In the centre of this area, p-type devices sitting in an n-well, surrounded on either side by n-type devices, all in a p-type substrate can be observed. The object of the study was to determine if a low concentration p-type implant is present below the n-type devices.

SIMS Depth Profiling of Delta-doped Layers in Silicon

Boron and germanium 6-doped silicon samples were studied using SIMS depth profiling on a Cameca IMS-4F instrument with O 2 + , N 2 + and Cs + primary beams at various energies and incidence angles. The depth resolution characteristics were compared. We show that, with experimental conditions being the same, the N 2 + primary beam provides for better decay lengths, while the leading edges of the profiles turn out to be significantly broadened because of the beam-induced roughness which develops at an early stage of silicon bombardment by N 2 + ions. The influence of ripple-like roughness on the SIMS profile shape is considered within the present simple analytical model. The effect of a modified layer on the SIMS profile depth was experimentally investigated. For profiles obtained with an N 2 + primary beam, it was shown that swelling of the modified layer produced by the implantation and trapping of primary particles shifts the profile as a whole toward the surface.

Ion microscopy evidence that La3+ releases Ca2+ from Golgi complex in LLC-PK1 cells.

The effect of La3+ on LLC-PK1 cells was investigated by ion microscopy, a mass spectrometry-based technique with a spatial resolution of approximately 0.5 micron. Cells were incubated with LaCl3 for 10 min. (1 mM) or 30 min (0.1 mM), and intracellular calcium distributions were measured with a Cameca IMS-3f ion microscope in cryogenically prepared cells. Compared with control cells, La3+ reduced total calcium in the Golgi complex by > 100 microM in both treatments, whereas other cellular regions, such as the nucleus and cytoplasm, remained largely unchanged. These two treatments were repeated on cells that were preincubated with 1 mM ouabain. The presence of ouabain in the medium increased the loss of calcium from the Golgi by about fourfold compared with the treatments without ouabain. The La3+ effect, therefore, was amplified by ouabain-induced Na+ loading, indicating a possible involvement of a Na+/La3+ exchanger. La3+ was detected within cells and its influx was facilitated by Na+ loading. These results suggest that La3+ may affect cellular calcium homeostasis by actions other than as a simple Ca2+ antagonist.

Imaging ion and molecular transport at subcellular resolution by secondary ion mass spectrometry

The transport of K +, Na +, and Ca 2+ were imaged in individual cells with a Cameca IMS-3f ion microscope. Strict cryogenic frozen freeze-dry sample preparations were employed. Ion redistribution artifacts in conventional chemical preparations are discussed. Cryogenically prepared freeze-fractured freeze-dried cultured cells allowed the three-dimensional ion microscopic imaging of elements. As smaller structures in calcium images can be resolved with the 0.5 μm spatial resolution, correlative techniques are needed to confirm their identity. The potentials of reflected light microscopy, scanning electron microscopy and laser scanning confocal microscopy are discussed for microfeature recognition in freeze-fractured freeze-dried cells. The feasibility of using frozen freeze-dried cells for imaging molecular transport at subcellular resolution was tested. Ion microscopy successfully imaged the transport of the isotopically tagged ( 13C, 15N) amino acid, l-arginine. The labeled amino acid was imaged at mass 28 with a Cs + primary ion beam as the 28( 13C 15N) − species. After a 4 h exposure of LLC-PK 1 kidney cells to 4 mM labeled arginine, the amino acid was localized throughout the cell with a preferential incorporation into the nucleus and nucleolus. An example is also shown of the ion microscopic imaging of sodium borocaptate, an experimental therapeutic drug for brain tumors, in cryogenically prepared frozen freeze-dried Swiss 3T3 cells.

Determination of hydrogen in silicates by secondary ion mass spectrometry

A quantitative procedure for the determination of hydrogen in silicates was developed for incorporation in the general procedure used with the Cameca IMS 4f ion microprobe for light and trace elements. The procedure employs a static 16O– primary beam and the ‘energy filtering’ technique. Moreover, it allows the analysis of samples placed on separate mounts with respect to standards and, in particular, of mineral grains directly in thin sections of rock. Factors influencing the hydrogen background were studied in order to ascertain the appropriate analytical conditions and to develop a specific procedure for the determination of low hydrogen contents. A low and reproducible background was obtained with simple heating and de-gassing of the sample. The background value was equivalent to 0.007–0.015% H2O and its fluctuation over a 1 week working session indicated that the detection limit was ≈0.015% H2O. The results obtained confirm that the use of high-energy ions reduces the influence of the matrix composition on the ionization of hydrogen (relative to that of Si); effects related to the structure of the sample appear to be negligible. Residual matrix composition effects are related, to a first approximation, to the Si content of the sample. As such effects could not be completely removed, two separate ion yields were used for samples with SiO2 contents in the range 27–51% and for rhyolites (≈72% SiO2). The reproducibility of the measurements was typically ≈3% and the accuracy for the former group of samples was 15% for H2O contents >0.1% and 30% for H2O contents of ≈0.05%.

Single zircon U-Pb geochronology of the Limpopo Belt by secondary ion mass spectrometry.

Single zircon U-Pb chronology was applied to help understanding the evolution of the Limpopo Belt in southern Africa. High mass resolution (M/ΔM=ca. 6000) obtained by a CAMECA IMS-3F ion microprobe was sufficient to determine Pb/U ratios of zircon crystals without any significant mass interferences. U-Pb ages of euhedral zircons from the belt cluster at around 3.2 Ga for the Central Zone and 2.8 Ga for the Northern Marginal Zone. The difference in age between the two zones can be explained by difference in protolith age. Timing of metamorphism was identified for the Northern Marginal Zone as 2 to 1.7 Ga which is younger than previously reported metamorphic ages of the Limpopo Belt.

Suppression of Cluster Ion Interferences in Glow Discharge Mass Spectrometry by Sampling High-Energy Ions from a Reversed Hollow Cathode Ion Source

The energy distributions of the ions produced in a reversed hollow cathode glow discharge ion source were studied using a Cameca IMS 3f mass spectrometer. Aluminum cathodes containing various impurities at concentrations of a few hundred parts per million (ppm) were used. Two prominent peaks were found in the energy distributions, corresponding to ions with high kinetic energies (formed in the negative glow region of the discharge) and ions with low kinetic energies (formed near the cathode potential at or near the extraction aperture in the base of the follow cathode). For Al + ions, the high-energy peak is more intense than the low-energy peak, while for Ar + ions the high-energy peak is much weaker than the low-energy peak due to efficient resonant charge exchange in the cathode dark space

18O tracer study of the oxidation of zircaloy‐4 in steam

AbstractThe corrosion resistance of Zircaloy‐4, used as fuel cladding in pressurized water reactors, in steam at 400°C is related to the annealing temperature used in fabrication. This change in corrosion behaviour appears to be related to the size and composition of intermetallic compound precipitates, which vary with annealing temperature.A SIMS study has been undertaken to clarify the mechanisms responsible for these variations in the initial stages of corrosion of Zircaloy‐4. A set of samples subjected to different annealing temperatures have been oxidized, initially in normal steam and subsequently in steam enriched in H2 18O. Corrosion mechanisms have been followed using depth profiling in a Cameca IMS 3F microscope together with three‐dimensional depth profiles and imaging of taper sections using a gallium microprobe (VG Scientific).Iron and chromium, present in intermetallics in the alloy, remain localized within the oxide scale. The size and frequency of these local concentrations of iron and chromium reflect the distribution of these elements in the alloy. There is, however, some diffusion of these elements into the surrounding oxide, the iron diffusion being greater than that for chromium. The 18O tracer studies indicate that grain boundary transport of oxygen dominates the initial oxide growth process for Zircaloy‐4.

Sample rotation during SIMS depth profiling in a Cameca IMS3F

SIMS depth profiles of a Be spike doped GaAIAs sample grown by MBE and a sputter deposited Al on Si film have been analysed in a Cameca IMS3F with and without sample rotation. The sample rotation was achieved using a stage (manufactured by Kore Technology) which maintains the alignment of the ion optical and rotational axes at any position on the sample surface. Significant improvement in depth resolution is shown for both materials' systems.

High precision [formula omitted] zircon geochronology using a small ion microprobe

A small geometry ion microprobe (Cameca ims 4f) has been successfully used for the routine measurement of 207Pb 206Pb ratios in individual zircons with a spatial resolution of $ ̌ -20 μm. In spite of the lower sensitivity of the small ion microprobe, resulting from operating at high mass resolution (M/ΔM > 4600) in order to resolve isobaric molecular interferences, we can discern Archean components whose ages differ by ⪰ 50 Ma. A single measurement requires 90 min of data acquisition; thus, a comprehensive study of a zircon population can be accomplished in a few days. Three sets of Precambrian zircons, analyzed earlier by other techniques, yielded ages which are within ± 2 σ of their “true” values. As our first “unknown” we analyzed zircons from a sample of orthogneiss collected from the Aravalli Craton of northwestern India. For this sample, we obtained a minimum age of 3281 ± 3 Ma (1σ), which we believe closely approximates the time of crystallization of the gneiss's igneous protolith.

Imaging of total intracellular calcium and calcium influx and efflux in individual resting and stimulated tumor mast cells using ion microscopy.

Ion microscopy was employed to investigate intracellular total calcium concentrations and calcium influx, and efflux in resting and antigen-stimulated tumor mast cells (RBL-2H3 cells). The nucleus, a perinuclear region which included the Golgi apparatus (Golgi region), and the remaining cytoplasm were spatially resolved with the Cameca IMS-3f ion microscope in cryogenically prepared cells. In resting cells the nucleus contained about 0.60 mM, the Golgi region about 1.2 mM, and the remaining cytoplasm about 1.0 mM total calcium. Antigen stimulation of rat basophilic leukemia cells resulted in a significant loading of calcium in all three cellular compartments. Antigen stimulation in the absence of extracellular calcium resulted in a significant loss of total calcium from all three intracellular compartments. Influx and efflux of calcium were measured simultaneously in resting and stimulated cells by using stable 44Ca in the extracellular solution, and by imaging mass 40 to determine the native intracellular calcium (40Ca) and mass 44 to localize the 44Ca that entered the cell from extracellular solution. After a 10-min incubation, 0.240 fmol of the total calcium per cell had been replaced with 44Ca, which amounts to about 33% of the total cell calcium. If antigen was present during this incubation there was an additional loss of 0.229 fmol of 40Ca and an added gain of 0.476 fmol of 44Ca per cell, which corresponds to a net increase in total intracellular calcium of 0.247 fmol.

SIMS depth profiling with sample rotation in a cameca IMS 3F

AbstractThe improvements in depth resolution and the suppression of sputter‐induced surface topography obtained using sample rotation during SIMS depth profiling in a Cameca IMS 3F are described. The sample rotation was achieved using a stage that maintains the alignment of the ion optical and rotational axes whilst allowing x–y translation to any position on the sample surface. The material systems studied were a Be‐spike‐doped GaAlAs sample grown by molecular beam epitaxy and a sputter‐deposited film of aluminium on silicon. Significant improvement in depth resolution is shown for buried features in both materials; the sputter‐induced ripple topography was suppressed in the analysis of the GaAlAs; for the aluminium on silicon sample the surface roughening was much reduced but some topography was still present even with sample rotation. The apparent interface width between the 1 μm thick aluminium film and the silicon substrate was reduced from 310 to 45 nm.

Inverse velocity trends in secondary ion mass spectrometry; a new method for quantification?

Secondary ions from the elements of As, Cu, Ni, P, and Zn, from two standard reference materials analysed with a Cameca IMS 3f SIMS instrument were found to exhibit strong exponential-like dependences on escape velocity, particularly over the higher emission energy range. These dependences were noted under O −, O 2 +, and Cs + primary ion beam conditions. After accounting for their known concentrations, the inverse velocity curves (secondary ion intensities corrected for instrument transmission and sputter yield effects plotted against the inverse of the velocity) were found to merge as infinite velocity was approached. These observations agree with quantum mechanical arguments used to describe secondary ion formation, and, in addition, suggests a new method for undertaking quantitative analysis by secondary ion mass spectrometry (SIMS). Quantification would be carried out by referencing infinite velocity values for each element of interest to that obtained from an element for which the concentration is already known.

Secondary ion inverse velocity plots from a cameca IMS-3f SIMS instrument

Transmission function calculations for a Cameca IMS-3f secondary ion mass spectrometer have allowed for the measurements of inverse velocity ( 1 v ) plots for Cu + and Cu − secondary ions emitted from a Cu substrate over the 6–250 eV (plus binding energy) emission energy range. Strong linear relationships were exhibited in these plots, particularly over the higher energy portion (> 80 eV). Such trends indicate an exponential dependence of the secondary ion yield on emission velocity, consistent with current surface ionisation theories. At energies below 80 eV deviations from this trend were observed particularly for the Cu − secondary ions. Comparison with 1 v plots for ions (F + and H +) known to be produced, to some extent, via a stimulated desorption process, suggests that the lower energy deviation exhibited by the Cu − secondary ions results from a desorption process. The possibility of near surface collisions is also considered.

Depths of Melting and Melt Extraction Beneath Mid-Ocean Ridges as Recorded in Melt Inclusions

Recent studies have shown that chemical compositions of primitive melt inclusions in olivine and plagioclase phenocrysts in mid-ocean ridge basalts (MORB) carry important information of process of melting and melt extraction beneath mid-ocean ridges (e.g., Sobolev and Shimizu, 1993). It is generally observed that variations of trace element abundances and abundance ratios in melt inclusions on small sampling scales (e.g., single dredge, single pillow) are very large, and can be adequately explained by melting models involving efficient extraction of small-degree melt fractions. This paper reports chemical variations in two primitive melt inclusion suites (33.7~ MidAtlantic Ridge and 36.5~ Mid-Atlantic Ridge, FAMOUS area) with distinct trace element characteristics, representing melting and melt extraction occurred at different depths. Major element compositions in melt inclusions and host minerals were determined with a JEOL 733 at MIT, and trace element abundances (Ti, V, Cr, Sr, Y, Zr, REE) were determined with a Cameca IMS 3f at WHOI. Only perfectly glassy primary inclusions were analyzed. Effects of postentrapment growth of host minerals were found to be typically 5 ~ 15%. Olivine (s9-91)- and plagioclase (Ansl-ss)

Residence of REE in Low-Temperature Eclogites from Ligurian Alps, North Western Italy: The Role of Accessory Minerals

The ophiolites of Ligurian Alps were subjected to pervasive re-equilibration under low-temperature eclogite facies conditions, as a result of a subduction event probably of Cretaceous-Eocene age (Ernst, 1976). Eclogitized Fe-Ti-gabbros developed the bimineralic assemblage of omphacite and Fe-rich garnet, with coronitic to mylonitic textures caused by stress gradient during synmetamorphic deformation. The involvement of fluids during eclogite facies metamorphism, probably related to the breakdown of hydrous minerals developed during the preceding ocean-floor metamorphism, is testified by the local occurrence of garnet (__. omphacite __+ rutile)veins. In coronitic eclogites, high pressure clinopyroxenes have different REE compositions which reflect the original distribution of the major igneous minerals (Messiga et al., 1994). Clinopyroxenes from mylonitic eclogites show homogeneous REE compositions, due to the enlargement of reaction domains into the shear zones. The eclogitic clinopyroxenes, as well as garnets, invariably show a marked LREEdepletion (Fig. 1), stronger than that of igneous diopside relics from coronitic eclogites which have LaN/SmN ~ 0.2. In order to unravel the REE redistribution during the eclogite facies metamorphism, accessory apatites and allanites from an eclogite sample were analyzed using a Cameca IMS 4F ion microprobe. modal percentage is lower than 1%. Other accessory phases are quartz and Fe-sulphides. Apatites display high REE contents (~ 103 x C1), their pattern is characterized by slight MREE-enrichment and negative Eu anomaly (Fig. 1). Allanites have extremely high amounts o f L R E E (,~ 105 x CI; Fig. 1), with a slight Nd-

Experimental Determination of Trace Element Partitioning Between Pargasitic Amphibole and Hydrous Silicate Melt

Our starting material is similar to that used by Mysen (1978), and is broadly analogous to a Kand Fe-free andesite. At the run conditions of our experiments (1.5GPa, 1000~ nearly H20-saturated), pargasite and subordinate clinopyroxene are the liquidus phases. Starting materials were synthesized from oxides and carbonates; trace elements were added as dilute nitrate solutions. The samples were sealed in Pt capsules with 10 wt.% H20, and run in a piston cylinder apparatus (fo2 ~ QFM) using a P-T history designed to promote equilibrium growth of a few large crystals. Electron microprobe analyses of the run products used a 20ttm, defocussed beam and a 10hA or 5hA beam current on crystals and glass, respectively. Trace elements were measured using a Cameca IMS-3F ion microprobe using a 15-50nA Oprimary beam. For each sample, multiple spots on each phase were analyzed, and the results for each phase were averaged. Isobaric molecular interferences were minimized by the use of an energy-filtering technique. Trace element concentrations were determined by comparing the 3~ isotopic ratios of the samples to those of silicate mineral and glass standards. Our quench glass contains > 10% H20, and ion yields relative to 3~ were higher in this hydrous glass than in an anhydrous glass of the same composition. The enhancement in yield is largest for Rb (+39%), Sr (+17%), and Ba (+ 20%). For the other elements we report, the enhancement is < 10%. All glass analyses were corrected for this effect. The estimated combined error in the trace element concentrations is -+20%. Partition coefficients were calculated from the ratio of the average 3~ count rate of an isotope in the amphibole to the average ~~ count rate in the glass, correcting for the differences in Si contents and the difference in ion yields due to the effect noted above. Reported errors reflect propagation of the larger of the counting statistics errors or the lt~ variability of the spot analyses.

Two-dimensional doping profiles from experimentally measured one-dimensional secondary ion mass spectroscopy data

Two-dimensional doping profiles can be determined from multiple one-dimensional secondary ion mass spectroscopy (SIMS) profiles using computed tomography techniques. The chemical nature of SIMS enables the measurement of both as-implanted and annealed profiles with this technique. Mechanical lapping was done of multiple samples to expose different faces of the substrates followed by one-dimensional SIMS measurements. Measurements have been done with a Perkin Elmer Model 6300 SIMS and a Cameca IMS-3f SIMS. Refinements have been made in the numerical alignment of the separate one-dimensional SIMS data sets, which lead to more accurate reconstructions of the two-dimensional profiles.

SIMS imaging of insulator surfaces

AbstractImaging of secondary ions emitted from bare insulator surfaces has been carried out on a Cameca IMS 3F secondary ion mass spectrometer without the use of electron beam, conductive grid or coating methods. This was accomplished by analysing secondary ions with kinetic energies ranging from 200 to 350 eV emitted from chargestablized samples. Charge stabilization was attained by placing the sample under various forms of specimen isolation. Images from both O− and Cs+ primary ion‐bombarded surfaces were collected, with several examples shown; O− provided the better spatial resolution due to improved sample potential stability. Mechanisms associated with charge stabilization and image distortion are elaborated upon with the aid of computer simulations.

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.