Secondary Ion Mass Spectrometry Method Research Articles

Influence of ion beam on optical properties of GaAs: Calculation using the fractional‐derivative‐spectrum method

AbstractSemiconductor GaAs (100) was implanted with In+ at a room temperature. Fluences of implanted ions were from 1x 1012 cm‐2 to 3x1013 cm‐2 and the energy was equal to 85 keV. The detectability of the indium content in near surface layer of GaAs has been studied with the use of the secondary ion mass spectrometry (SIMS). The depths distribution of a indium concentration measured by SIMS method ware compared with depth profiles calculated with the help of SATVAL code. It was noticed that calculated profiles are in a good agreement with the measured values. Additionally, the concentration of indium in the near surface layer increased with growing of the implantation fluence and a maximum of these profiles shift in the side of ions exposed surfaces of GaAs. This effect can be explained by self‐diffusion process of target atoms and indium during the implantation. The fractional derivative spectrum (FDS) model in connection with spectroscopic ellipsometry ES was used for particular optical analyses of implanted GaAs substrates. The FDS is especially promising technique when the limitations of the standard treatment by Lorentz shape line analysis occur and it is very helpful to extract basic information on relevant physical quantities from the detected εE2(E) spectra determined by spectroscopic ellipsometry. In particular, using spectroscopic ellipsometry and FDS, the critical points E1 and E1+Δ observed in the εE2(E) spectra in the implanted substrates have been investigated. The differences in complex refractive index and dielectric function (ε=ε1+iε2) between GaAs substrate before and implantation were observed. Moreover, the several nanometres thick oxide layer on GaAs surface was detected. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Damage engineering of boron-based low energy ion implantations on ultrashallow junction fabrications

Combination of transmission electron microscopy and secondary ion mass spectrometry methods and device characteristics are used to successfully study damage engineering of the B-based low energy ion implants. The depths and densities of the amorphizing (a-Si) layer (surface lattice damage) and the end of range (EOR) damage are found to correlate to ion mass (amu) and implant energy, which are scalable to the molecular ion implants and ultralow energy) implants. The B11 beam-line implant shows thinner both a-Si and EOR depths due to its smaller amu and lower energy, and the damage are well annealed under the current annealing conditions. The BF2 beam-line implant shows severe surface lattice damage by more amorphizing due to its larger amu and higher energy, and needs more thermal budget to annealing (recrystallizing). The B2H6 plasma doping (PLAD) shows moderate a-Si layer and less EOR damage than beam-line ones which attributes to B deposition as a screen so that there are no direct ion bombardments on Si wafer substrate. The BF3 PLAD shows similar damage behavior to the BF2 beam-line implant but with less lattice damage. The device performance evaluation confirms that the device processed by B2H6 PLAD shows better ION versus IOFF characteristics than those processed by BF2 and C2B10H12 molecular beam-line implants due to less damage and more complete annealing.

Inelastic ion-surface collisions: Understanding secondary emission of molecular ions

Electron transfer phenomena and inelastic ion-surface collisions lead to various processes of ionization: excitation of projectile/target atoms, secondary electron or atom/ion emission, etc. An important issue is the effect of electron exchange between the outgoing excited/ionized species and in particular, the effect of the chemical environment or surface composition on the outcome of the emission process. Secondary emission of molecular and/or cluster ions in the sputtering process has a large impact on the compositional analysis of materials. The problem arising out of 'matrix effect' in secondary ion mass spectrometry (SIMS) has largely been circumvented by the quantitative potential of the MCs+-SIMS method. However, it generally suffers from a low useful yield of MCs+ ions and in such case, MCs+2 molecular ions offers a better detection sensitivity. The present paper addresses the understanding of MCs+n (n = 1,2...) molecular ions formed in inelastic ion-surface collision processes.

Investigation of Local Hydrogen Distribution Around Fatigue Crack Tip of a Type 304 Stainless Steel with Secondary Ion Mass Spectrometry and Hydrogen Micro-Print Technique

In order to establish an appropriate method for measuring the local hydrogen content distribution around a fatigue crack tip in austenitic stainless steels, secondary ion mass spectrometry (SIMS) and the hydrogen micro-print technique (HMPT) were applied to a fatigue crack in a type 304 stainless steel fatigued in a hydrogen gas environment. The main results in this study are as follows. In the SIMS method, it is visualized that a high content of hydrogen exists in the plastic zone at a fatigue crack tip propagated in hydrogen gas, compared to that on a smooth area fatigued in hydrogen, though there is a measurement error based on false detection due to the edge effect regarding hydrogen in water vapor on the fatigue crack surface. On the other hand, hydrogen in the plastic zone is difficult to detect by HMPT. This is attributed to the difficulty for hydrogen atoms to be emitted from the sample in this case. To detect hydrogen, it is necessary to sputter the atoms forcibly. In addition, it is considered that to analyze the local hydrogen distribution around a fatigue crack tip with SIMS not only qualitatively but also quantitatively, reduction of the false detection due to the edge effect is necessary.

Characterization of an ultrashallow junction structure using angle resolved x-ray photoelectron spectroscopy and medium energy ion scattering

The control of dose and energy (and therefore depth distribution) of ion implantation in n-channel MOSFET (NMOS) ultrashallow junctions is vital. Therefore there is a need to provide reliable metrology. Since the standard sheet resistance probing method, and the dynamic secondary ion mass spectroscopy method used to calibrate it both become more problematic for very shallow junctions, other techniques need to be evaluated. Angle resolved x-ray photoelectron spectroscopy (AR-XPS) is investigated here as an additional, nondestructive, laboratory-based tool to characterize NMOS junctions. The arsenic depth distribution and chemical bonding configuration are investigated for a set of p-type wafers implanted at 2keV with nominal doses from 1×1015to2×1015at.∕cm2. The results are compared to those using medium energy ion scattering (MEIS). It is demonstrated that XPS is a useful nondestructive tool for obtaining dopant chemical bonding state, qualitative elemental and chemical state depth information without modeling, and quantitative information on overlayer film thickness. Modeling the AR-XPS data and comparison to trial depth structures can lead to a more quantitative, but crude, depth profile. The combination of AR-XPS and MEIS was also able to explain why secondary ion mass spectroscopy profiling measures an approximately 2% increase for 1×1015at.∕cm2 in apparent dose on annealing the arsenic as-implanted wafer.

Surface analysis of the size-fractioned urban aerosols by secondary ion mass spectrometry (ToF-SIMS)

AbstractThe secondary ion mass spectrometry method (ToF-SIMS) has been applied to the analysis of some mineral and organic species on the surface layers of airborne urban particulates. Particulate matter was collected on aluminum sheets of the 8-stage Anderson type cascade impactor from three different sampling sites in the city of Lodz, Poland, which were different in terms of aerosol source apportionment. The obtained results show that vehicle combustion products occur mainly in fine fraction with aerodynamic diameters below 1µm. The main contribution to the mineral components comes from direct and traffic related soil resuspension.

Investigation of Local Hydrogen Distribution Around Fatigue Crack Tip on a Type 304 Stainless Steel with Secondary Ion Mass Spectrometry and the Hydrogen Micro-print Technique

In order to establish an appropriate method for measuring the local hydrogen content distribution around a fatigue crack tip in austenitic stainless steels, secondary ion mass spectrometry (SIMS) and the hydrogen micro-print technique (HMPT) were applied to a fatigue crack in a type 304 stainless steel tested in a hydrogen gas environment. The main results obtained in this study are as follows. In the SIMS method, there is a measurement error based on the edge effect regarding hydrogen in water vapor on the fatigue crack surface, though it is visualized that a high content of hydrogen exists in the plastic zone at a fatigue crack tip propagated in hydrogen, compared to that on a smooth area fatigued in hydrogen. On the other hand, this hydrogen in the plastic zone is difficult to detect with HMPT. In this case, this is attributed to the difficulty for hydrogen atoms to be emitted from the sample. To detect the hydrogen, it is necessary to sputter atoms forcibly. In addition, it is understood that to analyze the local hydrogen distribution around a fatigue crack tip with SIMS not only qualitatively but also quantitatively, reduction of the error based on the edge effect is necessary.

Evaluating and Improving SIMS Method for Measuring Nitrogen in SiC

A multiple data point version of the industry standard, two data point raster-changing procedure is employed to measure low levels (< 1 x 1017 atoms/cm3) of nitrogen (N) in silicon carbide (SiC) by SIMS (Secondary Ion Mass Spectrometry). A current-changing procedure is also employed. Together, these are used evaluate the assumptions of the standard method, to separate and measure the components of background signal, and to improve upon the precision and accuracy of the standard method. The risk of poor precision in the two-point method is demonstrated, as is the improvement provided by the multiple-point method. Results show that, in addition to the wellknown N memory background, adsorption background can contribute significantly to the N signal. In general, establishing the presence of adsorption gas in this way can be used to warn of the presence of ionization background, which is not measurable per se.

SIMS-depth profile and microstructure studies of Ti-diffused Mg-doped near-stoichiometric lithium niobate waveguide

Ti-diffused planer waveguides have been fabricated on pure and Mg-doped near stoichiometric lithium niobate (SLN). Secondary ion mass spectroscopy method was applied to study the Ti diffusion in 1 mol% Mg-doped Z-cut SLN crystal. 100 nm Ti film has been deposited on LN substrate by e-beam evaporation at room temperature. Diffusion constant value for Mg-doped SLN is lower (1.84×10 −13 cm −2/s) than that of pure SLN. Mg-doped CLN also possesses low diffusion constant value of 1.27×10 −13 cm −2/s due to higher doping concentration of Mg (5 mol%). AFM topographic observation reveals that Mg-doped SLN shows lower surface roughness than Mg-doped CLN. The roughness (peak to valley) of the Ti-diffused Mg:SLN is 20 nm compared to 62 nm for the congruent LN waveguide. These features make Mg:SLN highly attractive for the fabrication of efficient waveguides.

Characterisation of molybdenum intermediate layers in Cu–C system with SIMS method

In the design of new high-speed chip generations a huge problem is bleeding off process heat during their operation. The installation of heat sinks onto such chips is necessary. Possible materials are copper-coated carbon composites. They combine high thermal conductivity with low density and a tailorable coefficient of thermal expansion (CTE). The low wettability of copper onto carbon necessitates a surface pretreatment. Flat slices of nitrogen-plasma etched vitreous carbon (Sigradur G) made up as a model system for carbon fiber material. The later serial fabrication of these fibers includes a hot pressing step after the deposition joining them to solid composites. It is simulated by a heat treatment step of the compound. The first sample series consisted of samples with 100 nm molybdenum and 500 nm copper layers (sputter deposited), as deposited and heat treated. The second run concludes samples without molybdenum layer but an additional 50 nm cap layer deposited after heat treatment. All samples were investigated with secondary ion mass spectrometry (SIMS), showing a diffusion of carbon into the molybdenum layer. Measuring MCs + secondary ions, both matrix elements and trace elements were detectable sufficiently.

Secondary-ion mass spectrometry of photosensitive heterophase semiconductor

The influence of positively charged ion bombardment and white light illumination on polycrystalline high-resistance photosensitive CdS–PbS semiconductor was investigated by secondary-ion mass spectrometry method. The illumination during ion sputtering was found to result in an ion yield decrease of some film components (Cd or PbO) and in increase of another one (Pb). The experimental data are explained by the model of a heterophase semiconductor resistant to degradation.

Investigation of 3-mercaptopropyltrimethoxysilane self-assembled monolayers on Au(111) surface

In this paper, preparation method of two-dimensional (2D) silica-like surface from self-assembled monolayers (SAMs) of 3-mercaptopropyltrimethoxysilane (MPTMS) on Au(111) surface is presented. The surface structure and morphology were characterized by scanning tunneling microscopy (STM) and secondary ion mass spectrometry (SIMS). In a first step, gold surface was imaged in order to find the topography. Then investigations were focused on MPTMS deposited on Au(111). Further steps like hydrolysis and condensation of MPTMS end-groups were performed and monitored by STM and SIMS methods. Hydrolysis and condensation reactions lead to 2D SiO 2 network called glass monolayer. It can be also described as 2D sol–gel processes. All procedures were performed in monolayer. When the state of end groups of MPTMS changes, i.e. when methoxy (Si–OCH 3) groups undergo hydrolysis to silanols (Si–OH) groups, the surface topography changes. The similar phenomena may be observed when silanols undergo condensation and siloxy (Si–O–Si) bonds are created.

Secondary-ion mass spectrometry of photosensitive heterophase semiconductor

The influence of positively charged ion bombardment and white light illumination on polycrystalline high-resistance photosensitive CdS–PbS semiconductor was investigated by secondary-ion mass spectrometry method. The illumination during ion sputtering was found to result in an ion yield decrease of some film components (Cd or PbO) and in increase of another one (Pb). The experimental data are explained by the model of a heterophase semiconductor resistant to degradation.

Investigation of nitrogen distribution in samples produced by ion-induced deposition of Cr films on aluminum under nitrogen ions bombardment

The paper describes the development of methods for hardening of pieces of aluminum alloys by ion-induced deposition of Cr–N films. We investigated the nitrogen distribution in the films and in the aluminum substrate. The method of secondary ion mass-spectrometry (SIMS) and a nuclear reaction method (NRM) were used in the study described. A computer model was developed that allowed us to describe the nitrogen distribution under the high temperatures in the growing film and in the interface substrate layers. The experimental results obtained agree well with the calculated data.

Sputtering of a polycyclic hydrocarbon molecule: TOF–SIMS experiments and molecular dynamic simulations

This study focuses on the desorption and ionization processes of an aromatic molecule containing several phenyl rings, 1,2,3,4-tetraphenylnaphthalene (TPN), adsorbed on a Au surface, via the comparison of experimental secondary ion mass spectrometry (SIMS) data and molecular dynamic (MD) simulations. The mass spectra and kinetic energy distribution (KED) measurements were obtained using both TOF–SIMS and MD simulation methods. For entire TPN molecules, a good agreement is observed between the calculated and experimental KEDs, except for high energies, where they start diverging. This difference is partly caused by the unimolecular dissociation of internally excited molecules over larger time intervals than those considered in the simulation. In turn, using an internal energy threshold to remove the most excited molecules from the calculated KEDs provides a better agreement with the experiment. The MD simulations also show that molecules surrounding the impact point of the projectile are sputtered with more kinetic energy and shorter emission times than molecules located farther away from it. The distinct emission mechanisms inducing these different energy spectra are identified by the analysis of the simulation results.

Nano-dimensional analysis for practical materials using the nano-beam SIMS apparatus

We have been developing the nano-beam secondary ion mass spectrometry (SIMS) apparatus, which can realize high spatial resolution and high efficiency of secondary ion detection. In this paper, the nano-beam SIMS method was introduced for the purpose of characterization for practical materials: contact holes. Contrasts of ion induced secondary electron (ISE) image and ion induced secondary ion (ISI) image were different. The difference was discussed with respect to information depth and chemical sensitivity. Elemental maps were obtained with nano-dimension and the maps provided many aspects of the sample. [DOI: 10.1380/ejssnt.2004.131]

Adhesion promotion of Cu on C by Cr intermediate layers investigated by the SIMS method.

Copper-carbon composites are candidate materials for heat sinks for high speed/high-performance electronic components. They combine high thermal conductivity with low density and a tailorable coefficient of thermal expansion (CTE). Because of the low wettability of carbon by copper, a thin layer of chromium can be deposited to promote both the adhesion and the thermal contact of copper with the carbon fibers. Therefore, in a first step layers of Cr and Cu were deposited by magnetron sputtering on plane vitreous carbon substrates (Sigradur G), which serve as a model for carbon fibers. From pull-off-adhesion measurements an interlayer thickness of Cr in the range of 2-10 nm was found to provide the optimal adhesion for 1 micro m thick copper overlayers. To model the later serial fabrication of the composite that involves a hot pressing step following the deposition, the C/Cr/Cu samples were heat treated at 800 degrees C under vacuum for 1 h. Adhesion on the heat-treated samples was superior in comparison to the untreated ones. To obtain information about the adhesion mechanism secondary ion mass spectrometry (SIMS) investigations were done on the depth distribution of the main elements copper, chromium, and carbon. Two samples, one as deposited and one subjected to heat treatment after deposition, were compared in this investigation. We found that heat treatment mainly modifies the distribution of Cr in the C/Cr/Cu system.

SIMS analysis of volatiles in silicate glasses: 1. Calibration, matrix effects and comparisons with FTIR

This paper describes microanalysis techniques using secondary ion mass spectrometry (SIMS) to measure the abundances and isotopic compositions of hydrogen, carbon, fluorine, sulfur and chlorine in volcanic glasses. SIMS measurement of total H 2O and total CO 2 abundances compare very well with measurements on the same glasses using vibrational spectroscopy techniques (FTIR). A typical 10-min SIMS measurement for volatile abundances is made on a singly polished specimen, sputtering a crater 15–30 μm in diameter and 2–3 μm deep, utilizing 1–5×10 −9 g of sample material. Detection limits are routinely <30 ppm H 2O, <3 ppm CO 2, and <1 ppm F, S and Cl. Measurements of δD, δ 13C and δ 34S in volcanic glasses are currently reproducible and accurate to 2–5‰, depending on the concentration of the element. Because of their spatial selectivity, the SIMS methods allow resolution of magmatic volatile signatures from those carried by secondary phases, which can sometimes plague traditional vacuum extraction methods that require large amounts of sample (tens to hundreds of milligrams). Ease of sample preparation, rapid analysis and high sensitivity allow SIMS to be applied to volatile analysis of small samples such as melt inclusions, in which large numbers of individual analyses are often required in order to obtain a representative sample population. Combined abundance and isotopic composition data for volatile elements provide coupled constraints on processes relevant to magma genesis and evolution, including degassing, magma contamination, mixing, and source variability.

Application of the method of secondary-ion mass spectroscopy to the study of heterodiffusion in alkali-halide crystals

The present paper gives the results of investigations of the high-temperature diffusion of Na and Mg ions into single crystals of potassium bromide by the method of secondary-ion mass spectrometry (SIMS). It is demonstrated that the diffusion profiles are nonelementary in character, and the diffusion in the near-surface layer is decelerated. To determine the volume diffusion coefficient, the diffusion profiles must be approximated for depths ≥1 μm. The efficiency of the procedure for determining the diffusion coefficient is confirmed by a comparison of the diffusion coefficients for Na ions determined in the present work with their values obtained by other methods having high reliability and measurement accuracy. The diffusion coefficients of the magnesium impurity are determined for various initial chemical states.

Characterisation of Cr intermediate layers in Cu–C-system with SIMS method

In the design of new high speed chip generations, the greatest problem is to bleed off process heat during their operation. The installation of heat sinks onto such chips is necessary. A copper–carbon (Cu–C) composite is one possible material. It combines high thermal conductivity with low density and tailorable coefficient of thermal expansion (CTE). Because of low wettability of carbon by copper, a thin layer of chromium (Cr) has to be deposited first to contact copper with the carbon fibers. The optimization of processing parameters was done on vitreous carbon substrates (Sigradur G) as a model for carbon fibers. Onto these substrates, 2 nm chromium and 1 μm copper were deposited. In the later serial fabrication of the composite, a hot pressing step will follow the deposition, which is simulated with a heat treatment of the compound. Secondary ion mass spectrometry (SIMS) investigations were done to obtain information on the depth distribution of the main elements copper, chromium and carbon. Two samples, one as deposited and one subjected to a heat treatment after deposition are compared in this investigation.