AES Profiling Research Articles

The electrical and material properties of MOS capacitors with electrolessly deposited integrated copper gate

The electrical properties of electroless-deposited barriers were studied using metal-oxide-silicon (MOS) capacitors with thin (14 nm) thermal oxide. Three different metal electrodes were deposited on a thin sputtered Co seed layer: (a) sputtered Al, (b) electroless Co(W,P) and (c) electroless multilayer of Co(W,P)/Cu/Co(W,P). The study includes thermal stress in vacuum in the 300–600°C temperature range, for periods of 30 min to 4 h, followed by electrical characterization. The high-frequency capacitance versus voltage ( C– V) characteristics of the capacitors was near ideal after annealing at 300–500°C for 30 min. After annealing at higher temperatures for longer times the inversion capacitance increased above the ideal high-frequency value while the flat band voltage remained unchanged. The minority carrier lifetime, as obtained from transient capacitance analysis, was in the range of 60 μs for samples annealed at temperatures below 500°C. It dropped for the samples with copper layers to 12 μs after 520°C anneal for 2 h and to 1 μs after 600°C for 4 h while remaining in the range of 50–60 μs for the samples with either electroless barrier or aluminum. AES profiling indicated that the copper profile remained unchanged after annealing at temperatures up to 500°C anneal for 30 min. Above 520°C, the copper profile showed significant diffusion onto the Co(W,P) barrier layer underneath and much less diffusion onto the Co(W,P) capping layer above.

Depth Profiling Study of the CdTe/CdS/ITO/Glass Heterostructure with AES and GIXRD

In this work we use Auger electron spectroscopy depth profiling and grazing incidence X-ray diffraction (GIXRD) to study chemical composition and structure of the CdTe/CdS/ITO/glass heterostructure. The CdS layer was deposited on ITO (In2Sn2O7–x) substrates by chemical bath deposition and the CdTe film was deposited by double-step close space sublimation. We found by AES profiling a strong intermixing at the CdS/ITO and CdS/CdTe interfaces, confirmed by GIXRD and evidences of two diffusion steps for the CdS into the ITO matrix. Additionally, the CdS/ITO structure was separately investigated in order to know the influence of the substrate roughness on the heterostructure conformation. The morphology of the ITO substrate and the as-deposited CdS layer was studied by atomic force microscopy. The use of GIXRD showed to be useful to study the entire CdTe/CdS/ITO/glass heterostructure. The ITO roughness has proved to be an influencing factor in the structural features and suggested that CdS roughness can also influence the observed composition profiles.

Electrochemical and analytical (XPS and AES) study of passive layers formed on Fe-Ni alloys in borate solutions

Passivation of Fe–Ni alloys (25, 50 and 75 Ni at.%) in borate buffer solution (pH 9.2) at +0.2 V/SCE has been studied by electrochemical methods (polarization curves, capacitance measurements and dissolution kinetics). The depth composition, chemical bonding and thickness of passive layers are determined by AES and XPS depth profiling experiments. Their structure consists of a thin enriched Ni(OH)2 outer layer above a thicker internal Fe-rich layer (Fe3+ and deeper Fe2+ oxidized species) of increasing thickness with the Fe alloy concentration. The presence of small amounts of internal NiO is also depicted in the Ni 75 at.% passivated alloy at short polarization times, in agreement with a potential analysis carried out during passive film dissolution kinetics in Na2SO4 solution (pH 3). In the underlying metallic alloy, a significant Fe depletion (and a simultaneous Ni enrichment) is observed after the first few minutes of polarization; afterwards, a slow decrease of the external Ni film content takes place, causing filmng film thinning. This can be interpreted by a two-step film formation mechanism consisting of fast initial selective oxidation of iron followed by slow preferential Ni dissolution. Copyright © 2000 John Wiley & Sons, Ltd.

A novel metal ion source for preparing hard coatings

A novel metal ion source, Electron Beam Evaporation Metal Ion Source, has been developed for material modifications. This ion source is based on the electron beam evaporation technology. It can provide gaseous, solid or gaseous and solid mixed intense ion beams for preparing a variety of thin films. In this ion source, a focusing electron beam is used to bombard and vaporize the metal or other solid element within same chamber where the metal or solid atoms are ionized and plasma medium from which ions are extracted is formed by arc discharge. A small aperture diameter extraction system is used for extracting the ion beam from this source. Ion beams of a series of elements, which include C, W, Ta, Mo, Cr, Ti, B, Cu, Ni, Al, Ar, N, C+N, Ti+N, Cr+N, etc., have been extracted. The source has a 3.6 cm extraction diameter. The beam energy ranges from 0.3 to 4 keV for single charge state ions, and the maximum beam current extractable is over 90 mA. The source has been used for preparing hard coatings. The films of carbon nitride and titanium nitride have been synthesized by direct deposition with C+N and Ti+N mixed ion beams. The results have shown to exhibit very high hardness value for carbon nitride films. The microhardness is up to HK 5800 kgf/mm2. In comparison with other methods, it is also to exhibit higher hardness value for titanium nitride coating. The highest hardness value obtained for titanium nitride is about 3000 kgf/mm2. The AES profile shows that there is a good intermixture between coating and substrate for both films. The principle, structure and performance of this ion source will be described. The preliminary results for forming hard coatings are also presented in this article.

Study on the ZrO 2–Y 2O 3/Fe interface

XPS measurements of the electron binding energy are made for the elements Zr, Y, Fe, and O at different depths to understand the effect of oxygen ion bombardment on the interface between a ZrO 2–Y 2O 3 film and an Fe substrate. The results show that (FeZr)O 1+ x ( x=1–<2) is formed at the interface as a result of the bombardment and reaction of depositing atoms and ions. The AES profile shows a broad transient region about 40 nm wide. Carbon contamination, a result of residual gases in the chamber during r.f. magnetron sputter deposition, is also discussed.

Depth distribution and bonding states of phosphorus implanted in titanium investigated by AES, XPS and SIMS

The depth distribution of phosphorus implanted in titanium at 20 keV with doses ranging from 1×1015 to 3×1017 cm−2 was investigated by AES, SIMS and XPS. For small doses (⩽1016 cm−2) Gaussian-like phosphorus profiles have been observed. For doses >1017 cm−2 the depth profiles suggest that a TiP-like surface layer is formed without additional thermal treatment. In the implanted layer a certain amount of oxygen was found. Factor analysis of the spectra obtained during AES and XPS depth profiling proved that the surface region of the implanted samples is composed of Ti metal, surface oxide and Ti phosphide, which is produced at high doses. From P L2,3 VV Auger spectra the existence of a second bonding state of phosphorus is deduced, which is distinguished from TiP by differences in the peak shape and position. This species is distributed mainly in a narrow profile located at a depth near the projected range of the phosphorus ions, i.e. in the region of maximum lattice defects. It is attributed to phosphorus on interstitial sites. The amount of this species reaches saturation for a dose of ∽1017 cm−2. © 1998 John Wiley & Sons, Ltd.

Determination of the inelastic mean free path of electrons in GaAs and InP after surface cleaning by ion bombardment using elastic peak electron spectroscopy

Abstract The inelastic mean free path (IMFP) of electrons is an important material parameter needed for quantitative AES, EELS and non-destructive depth profiling. The distinction between the terms for IMFP and the attenuation length (AL) has been established by ASTM standards. A practical experimental method for determining values of the IMFP is elastic peak electron spectroscopy (EPES). In this method, experimentally determined ratios of elastically backscattered electrons from test surfaces and from a Ni reference standard are compared with the values evaluated theoretically. The present paper reports systematic measurements of the IMFP by EPES for GaAs and InP. They are carried out in two laboratories using two different electron spectrometers: a CMA in Budapest and DCMA in Warsaw. Prior to measurements, the samples were amorphized by high-energy Ar + ions (100–400 keV), and the surface composition was determined by quantitative XPS. Argon cleaning produces enrichment of samples in the surface layer in Ga (80%) and In (70%), respectively. The experiments refer to a such modified sample surface that was considered in Monte Carlo calculations. The experimental data were analyzed using calibration curves from Monte Carlo calculations which account for multiple elastic scattering events. This approach has been used previously for elemental solids and is now extended to amorphized binary compounds. The experimental values of IMFP obtained in both laboratories exhibited a reasonable agreement with the available literature data in the 0.1–3.0 keV energy range. With respect to the information depth of EPES, the experimental results refer to the bulk composition within a reasonable extent.

A protective coating of Silicate on zincplate

AbstractA protective chemical conversion coating, developed on zincplate from a silicate aqueous solution, was found to be more effective in anticorrosive performance than molybdate, tungstate and some heteropoly acid conversion coatings. The relative atomic percent content (A.C. %) of the film, obtained from the constant elemental composition region of the AES profile curves, were oxygen 59.2 zinc 5.9% silicium 19.1%, nitrogen 2.7%, sulfur 4.2%, phosphorus 3.6% and carbon 5.3%. The results of XPS analysis showed that zinc existed as zinc sulfide in the surface layer of the film, while as zinc oxide in the internal layer of the film.

A protective coating of P-Mo-V heteropoly acid on steel

The corrosion resistance of chemical conversion coatings formed on mild steel from various P-Mo-V heteropoly acid solutions has been compared with that formed by the salt water dip, CuSO4 spot and H2S tarnish test. The results show that the passivation treatment with Na4PMo11VO40 gives the best protective performance. XPS and AES analyses of the conversion coating of Na4PMo11VO40 heteropoly acid Mo show that Fe, Mo, V and P are mainly present as Fe (III), Mo (VI), V (V) and P (V) respectively in the outerlayer of the film, while the above elements in the inner layer of the film exist partly in some lower valency state with the exception of P. The relative atomic percentages (A.C. %) of film composition obtained from the elemental composition constant region of the AES profile curves are Fe 1.7%, P 10.0%, Mo 34.4%, V 2.7%, O 50.4% and C 0.8%.

Nitrogen incorporation during N 20- and NO-oxidation of silicon at temperatures down to 600°C

The preferred incorporation of nitrogen in the SiO x transient layer near the SiO 2/Si interface was investigated using N 20- and NO-oxidation at temperatures from 1200°C down to 600°C and 20 s to 135 min process time. The peak nitrogen content, measured by AES and SIMS depth profiling, was accumulated with a high starting rate during N 2O-oxidation. This leads to a temperature-dependent concentration level of nitrogen of 4.5 at.% down to 0.25 at.% at the lowest temperature. An exponential fit of the peak nitrogen concentration (N peak) against reciprocal temperature gives an apparent activation energy of about 0.45 eV under the conditions used here at rapid thermal and at conventional furnace oxidation. After longer process time, e.g. 270 s to 800 s, a further low rate nitrogen accumulation at the SiO 2/Si interface was measured. This also holds at reduced temperatures down to 600°C, independent of the type of preoxide grown by dry 0 2-oxidation or by chemical vapor deposition (CVD). The NO-oxidation leads to a more than three times higher peak nitrogen level, dependent on temperature and time. A low thermal budget gate oxide preparation with nitrogen stabilization of the interface seems to be possible at 800C with not more than 30 s to 40 s process time using a CVD preoxide and diluted NO.

A protective‐decorative Cathodic conversion coating on steel

AbstractA decorative conversion coating was formed on mild steel from a solution of sodium molybdate and phosphate by cathodic treatment. Anodic corrosion curves demonstrated the good anticorrosive ability of the coating formed. The results of XPS analysis showed that iron existed as iron (II) and iron (III) in the film; molybdenum existed as molybdenum (VI) in the surface layer of the film, while as molybdenum (VI) and molybdenum (IV) in the inner layer of the film; phosphorus in the film was present in the pentavalent state. The relative atomic percent content (A.C.%) of the film was obtained by AES profile to be oxygen 58.6, molybdenum 21.3, phosphorus 10.2, iron 6.5 and carbon 3.4.

Thermal Stability and Interaction Between SiOF and Cu Film

AbstractIn this work, we study the thermal stability and interaction between SiOF and Cu. Blanket SiOF films with various F concentration were deposited by PE-CVD. A dielectric constant as low as 3.2 was obtained. Copper were deposited on these SiOF and a series of post-deposition anneal were performed. Dielectric constant of SiOF was measured after deposition and again after anneal. AES and SIMS depth profile are utilized to determine the interdiffusion between Cu and SiOF under different annealing conditions. Breakdown voltage and dielectric constant were determined form C-V and I-V measurement using a MIS ( Cu/ SiOF/ p-Si) diode. This results of leakage current measurement and flat band shift measurement suggest that the fluorine in the SiOF film will retard the cu diffusion.

Adhesion of ceramics to Inconel 600 under various chemical conditions

AbstractTwo types of catalytic ceramic coating for steam reforming were adhered to the surface of an Ni‐based alloy, Inconel 600, by sintering at high temperatures (1000°C) in atmospheric air. The interfaces were subsequently investiagated with AES, SAM and depth profiling after being submitted to a direct‐pull test to obtain a measure of the adhesion strength. It was found that the adhesion of the Mg‐rich coating was caused mainly by diffusion of Mg from the ceramic into the Cr2O3 scale of the metal substrate. After reduction in H2 (activation of the Ni catalyst), a substantial drop in the adhesion strength was found. This was caused by metallization of Ni‐rich islands in the interface zone formed on the metal during sintering. These findings suggest that firing temperature with lower oxygen partial pressure (during sintering) will lead to a more stable adhesion strength. The other, Al‐rich coating had a much weaker adhesion strength compared to the Mg‐rich coating.

RTA-Treated Ohmic Contacts To GaAs Containing WSiN Barriers

AbstractFor III-V device operation at 300 °C or above ohmic contacts have to consist of multilayered systems comprising an amorphous diffusion barrier. The contact system Au/Pt/Ti/WSiN/ Au/Ge/Ni-n-GaAs (n ≈ 5.1017 cm−3) has been developed and optimized with respect to the parameters of the barrier as well as the internal Au/Ge/Ni layers. The WSiN layer was deposited via reactive dc magnetron sputtering, the other layers by electron beam evaporation without breaking the vacuum. Annealing has been performed in a halogen lamp furnace. The contact resistance Rc as determined by TLM structures was measured as function of the annealing temperature and time. It was found that short-time annealings lead to a broad Rc minimum at 0.1 ωmm. For such Rc's the Au/Ge/Ni layer thicknesses must be ≥ 20/10/6 nm. Extended microstructural analysis was accomplished by XTEM/EDS and by AES and SNMS depth profiling. The typical alloying depth of the contact in the GaAs has been found to be about 50 nm, i.e. smaller than for the conventional Au/Ni/AuGe contact. The secondary phases formed (Au(Ga), NiGe(As)) are similar. With annealing conditions producing the desired Rc value, both Au(Ga) and NiGe(As) were observed in a bamboo-like arrangement at the metal-semiconductor interface. Degradation of Rc could be attributed to burying of the nickel-rich phases beneath gold-rich phases. This contact system is stable up to ≈ 300°C.

High-temperature oxidation of (Ti,Pd)N and (Cr,Pd)N coatings studied with AES and XPS sputter depth profiling

(Ti,Pd)N and (Cr,Pd)N coatings with Pd content of 10 at% were deposited on polished high-speed steel substrates by reactive magnetron sputtering using a multiple target technique. The coatings were annealed in air at temperatures between 350 and 700°C. At all temperatures the oxidation rate of (Ti,Pd)N is increased as compared with pure TiN. The oxide layers consist of TiO 2 on top and a Ti-oxynitride layer below. The TiO 2 layers grow according to a parabolic diffusion law with an activation energy of 135 kJmol −1 (TiN 184 kJmol −1). For (Cr,Pd)N the Cr 2O 3 layers grow according to a parabolic diffusion law with an activation energy of 113 kJmol −1 (CrN 123 kJmol −1). The increase of the oxidation rate with respect to CrN is much smaller than in the case of (Ti,Pd)N. The results can be explained by a different mobility of Pd in (Ti,Pd)N and (Cr,Pd)N according to the ratios of the atomic radii of the respective metallic components.

GaAs/AlAs superlattice as a proposed new reference material for sputter depth profiling

AbstractA GaAs/AlAs superlattice growth by metal–organic chemical vapour deposition is being proposed as the single crystalline multilayer reference material for sputter depth profiling. This material was characterized by transmission electron microscopy experiments, which showed that the interface between GaAs and AlAs is atomically flat. The preliminary depth profiling experiments were carried out by AES and SIMS.The AES experiments were performed using a Perkin‐Elmer SAM 660 scanning Auger microprobe and the SIMS experiments were carried out using a VSW multitechnique XPS/SIMS surface analysis system.The AES and SIMS sputter depth profiling experiments proved that the depth resolution was found to be almost constant for each interface when an Ar+ beam was used for sputtering. Therefore the sputtering‐induced roughness is very small for this material with Ar+ beam profiling, the depth resolution deteriorated as a function of depth, indicating oxygen ion beam‐induced surface roughening.For both AES and SIMS, the depth resolution improved for ion beams with lower kinetic energy and more glancing angles of incidence.

Iridium silicides obtained by rapid thermal annealing

Iridium silicides formation by RTA in an Ar atmosphere or under vacuum has been studied for several temperatures in the range of 350–500°C. For the samples annealed in argon atmosphere, oxygen is incorporated during the RTA process, slowing down the reaction at the interface or even stopping it. In this case, no clear compound, Ir 1Si 1 or Ir 1Si 1.75, could be identified neither from the RBS spectra nor from the AES profiles. On the other hand, when the anneal is performed under vacuum, silicidation takes place. In samples processed at 400°C in these conditions and processing time shorter than 45 s only the Ir 1Si 1 compound was formed. For longer annealing time, Ir 1Si 1.75 appeared too. At higher temperatures, even for very short processing time, Ir 1Si 1.75 was formed.

Compact data processing and control system for SIMS and AES

An improved version of a data processing and control system has been used with state-of-the-art AES and SIMS instruments. It consists of a mainframe with CPU, buffer and IEEE 488 interface to a host computer and a range of plug-in submodules. Its features include three-dimensional analysis, imaging, multichannel spectra and sample bias control. The performance of the system has been tested by AES and SIMS depth profile measurements of Si-Ge multilayers.

Rotational Auger depth profiling of a GaAs/AlGaAs multilayer structure

A superlattice sample consisting of 200 alternating 5 nm layers of GaAs and Al0.45Ga0.55As was analyzed to explore some of the factors affecting depth resolution in rotational depth profiling by AES, including coincidence of sample rotation and probe beam axes, stability of analysis position and probe beam current density. Because of the periodic nature of the layers involved, it was possible to detect very small (< 2 nm) changes in surface topography. A mathematical model is proposed which explains the unusual features observed in the AES profile.

AES, XPS and TEM characterization of metal/oxide multilayers

Multilayer structures for application in microelectronics, hard and wear resistant as well as optical coatings are becoming increasingly complex. Therefore, there is a permanent need for new model multilayer structures appropriate for high resolution depth profiling studies which are helpful for the interpretation of everyday analytical results. A new type of metal/oxide multilayer structure composed of alternating Cr, Ni, NiO and Cr 2O 3 layers with a total thickness of about 475 nm was sputter deposited onto a smooth silicon substrate. By TEM investigations we found a columnar crystalline structure of Ni, Cr and NiO layers with a comparable size of crystal grains while the Cr 2O 3 layer showed a partial amorphous structure with a small amount of a crystalline phase. Compositional depth profiles of the model multilayer structure were obtained with Auger and X-ray photoelectron spectroscopy on stationary and rotated samples. The AES and XPS depth profiles are discussed with respect to different instrumental parameters and the influence of crystalline and amorphous structures on depth resolution. The AES depth profiling of stationary samples, using a unidirectional ion beam, shows an evident beneficial influence of the oxide sandwich layers on depth resolution.