Auger Electron Spectroscopy Depth Research Articles

Improvement of thermal stability of Ta-N film in Cu metallization by a Zr-Si interlayer

Ta-N (10 nm)/Zr (20 nm) film was grown on n-type (100) silicon wafer at various substrate temperatures in a rf magnetron sputtering system, followed by in situ deposition of Cu. The Cu/Ta-N/Zr/Si samples were subjected to thermal annealing up to 800 ℃ under the protection of pure nitrogen gas. In order to investigate the effect of insertion of a thin Zr layer under Ta-N film on Ta-N diffusion barrier performance in Cu metallization, Cu/Ta-N/Zr/Si contact system was characterized by X-ray diffraction (XRD), four-point probe (FPP) measurement, scanning electron microscopy (SEM), and Auger electron spectroscopy (AES) depth profile. The results reveal that the microstructure of Ta-N films deposited on Zr is amorphous at different substrate temperatures. The barrier breakdown temperature of Ta-N/Zr film is about 100°C higher than that of Ta-N. It can effectively prevent the diffusion of Cu after annealed at 800°C. The improvement of diffusion barrier performance may be due to the production of Zr-Si layer with low contact resistivity after annealed at 800°C.

Extremely Thermal Stable Ni/W/TaSi<sub>2</sub>/Pt Simultaneous Ohmic Contacts to n-Type and p-Type 4H-SiC

Studying the ohmic contacts formed on ion-implanted SiC layers is fundamental to understand and to predict the behavior of practical devices. Ohmic contacts to n- (1×1019 cm−3) and p-type (1×1020 cm−3) ion-implanted 4H-SiC using Ni/W/TaSi2/Pt were investigated. No degradation of the specific contact resistance nor a minute change of the surface morphologies was observed after 300 h of 500 oC thermal treatment in air. From auger electron spectroscopy (AES) depth profiles, it was found that the oxidation of the protective platinum silicide overlayer significantly slowed down further migration of oxygen to the SiC interface. In addition, Pt and W played the role of mutual blocking, which guarantees the stability of the contact. This research suggests that the contacts are very promising for applications in harsh environments, where the simultaneously completed both on n-and p-type stability ohmic contacts is crucial.

Sputtered PdO Decorated TiO2 Sensing Layer for a Hydrogen Gas Sensor

We report a sputtered PdO decorated TiO2 sensing layer by radiofrequency (RF) sputtering methods and demonstrated gas sensing performance for H2 gas. We prepared sputtered anatase TiO2 sensing films with 200 nm thickness and deposited a Pd layer on top of the TiO2 films with a thickness ranging from 3 nm to 13 nm. Using an in situ TiO2/Pd multilayer annealing process at 550°C for 1 hour, we observed that Pd turns into PdO by Auger electron spectroscopy (AES) depth profile and confirmed decorated PdO on TiO2 sensing layer from scanning electron microscope (SEM) and atomic-force microscope (AFM). We also observed a positive sensing signal for 3, 4.5, and 6.5 nm PdO decorated TiO2 sensor while we observed negative output signal for a 13.5 nm PdO decorated one. Using a microheater platform, we acquired fast response time as ~11 sec and sensitivity as 6 μV/ppm for 3 nm PdO under 33 mW power.

A Thermally Stable NiZn/Ta/Ni Scheme to Replace AuBe/Au Contacts in High-Efficiency AlGaInP-Based Light-Emitting Diodes

We developed NiZn/(Ta/)Ni ohmic contacts to replace expensive AuBe/Au contacts commonly used in high-efficiency AlGaInP-based light-emitting diodes (LEDs), and compared the electrical properties of the two contact types. Unlike the AuBe/Au (130 nm/100 nm) contact, the NiZn/Ta/Ni (130 nm/20 nm/100 nm) contact shows improved electrical properties after being annealed at 500°C, with a contact resistivity of 5.2 × 10−6 Ω cm2. LEDs with the NiZn/Ta/Ni contact exhibited a 4.4% higher output power (at 250 mW) than LEDs with the AuBe/Au contact. In contrast to the trend for the AuBe/Au contact, the Ga 2p core level for the NiZn/Ta/Ni contact shifted toward lower binding energies after being annealed at 500°C. Auger electron spectroscopy (AES) depth profiles showed that annealing the AuBe/Au samples caused the outdiffusion of both Be and P atoms into the metal contact, whereas in the NiZn/Ta/Ni samples, Zn atoms indiffused into the GaP layer. The annealing-induced electrical degradation and ohmic contact formation mechanisms are described and discussed on the basis of the results of x-ray photoemission spectroscopy and AES.

흑색 코발트 태양 선택흡수막의 열퇴화

Black cobalt solar selective coatings were prepared by using an electroplating method. The changes in the optical properties of the black cobalt selective coating due to thermal degradation were analyzed by using the Auger electron spectroscopy (AES) and spectrophotometer. The black cobalt selective coating was prepared on a copper substrate by using a synthesized electrolyte with and KSCN at a current density of for 45s ~ 60s. Its optical properties were a solar absorptance () of the order of 0.80 ~ 0.84 and a thermal emittance () of 0.01. From the AES depth profile analysis of heated sample, thermal degradation of the black cobalt selective coating heated for 33 hours at temperature of occurred primarily due to interdiffusion at interface of cobalt and copper substrate. This results were predictable that the decreases due to the thermal oxidation and diffusion.

Controlling the Magnetic Properties of Cr-Implanted Co/Pt Multilayer Films Using Ion Irradiation for Planar Patterned Media

We have investigated the modification of the microstructure and magnetic properties of Co/Pt multilayer films with various layer structures using ion beam irradiation. Cr/[Co/Pt] multilayer films prepared by a magnetron sputtering deposition on a surface oxidized Si substrate were irradiated by 30 keV Kr+ ion beam with various ion doses from 1×1014 to 5×1015 ions/cm2. The modifications of magnetic properties and microstructures due to Kr+ ion irradiation depended on Co/Pt layer structures. The as-prepared [Co(0.4 nm)/Pt(0.45 nm)]15 multilayer films were confirmed to exhibit the square shaped M-H loop and the perpendicular easy axis with a saturation magnetization of 620 emu/cc and coercivity of 1.1 kOe. After the irradiation with ion dose of 5×1015 ions/cm2, the easy axis changes from perpendicular to in-plane direction. The coercivity and saturation magnetization decrease down to 2% and 13% of its original values, respectively. The decrease of coercivity and saturation magnetization is due to the implantation of the Cr atom in the top most layers into Co/Pt multilayer films caused by Kr+ ion irradiation, as confirmed from Auger electron spectroscopy (AES) depth profiles.

Effect of Substrate Temperature on the <I>In-Situ</I> Formation of Crystalline SiC Nanostructured Film Using Ultra-High-Vacuum Ion Beam Sputtering

In this paper, we have investigated the effect of substrate temperature on the in-situ formation of crystalline SiC (c-SiC) nanostructured film using ultra-high-vacuum ion beam sputtering (UHV IBS). The phase transformation, bonding behavior, morphology, composition and interdiffusion of the SiC nanostructured film were examined by X-ray diffraction, Raman spectra, high resolution scanning electron microscopy (SEM) with the attached energy dispersive X-ray detector and Auger electron spectroscopy (AES) depth profile, respectively. The in-situ formation of c-SiC was through interdiffusion and reaction between the sputtered carbon (C) and the crystalline Si (c-Si) substrate at high temperature. The amorphous-like C microstructure is stable up to 500 degrees C and transformed into a new phase of c-SiC together with the remained C at 600 degrees C. Complete C and Si reaction was found at 700 degrees C from Raman spectra without any C peaks. The main diving force for the c-SiC formation is the thermal energy to activate the large interdiffusion between C and c-Si which was detected from AES depth profile. Also, a nanoweb-like morphology of the c-SiC was observed on the surface of film from the SEM image. Therefore, the c-SiC nanostructured film can be obtained at 700 degrees C using in-situ UHV IBS process, which is much lower than conventional CVD c-SiC.

High Temperature Post-deposition Annealing Studies of Layer-by-layer (LBL) Deposited Hydrogenated Amorphous Silicon Films

AbstractHigh temperature post-deposition annealing studies were done on hydrogenated amorphous silicon thin films deposited by plasma-enhanced chemical vapour deposition (PECVD) using the layer-by-layer (LBL) deposition technique. The films were annealed at temperatures of 400 °C, 600 °C, 800 °C and 1000 °C in ambient nitrogen for one hour. Auger electron spectroscopy (AES) depth profiling results showed that high concentration of O atoms were present at the substrate/film interface and at film surface. Very low concentration of O atoms was present separating silicon layers at regular intervals from the film surface and the substrate due to the nature of the LBL deposition and these silicon oxide layers were stable to high annealing temperature. Reflectance spectroscopy measurements showed that the onset of transformation from amorphous to crystalline phase in the LBL a-Si:H film structure started when annealed at temperature of 600 °C but the X-ray diffraction (XRD) and Raman scattering spectroscopy showed that this transition only started at 800 °C. The films were polycrystalline with very small grains when annealed at 800 °C and 1000 °C. Fourier transform infrared spectroscopy (FTIR), measurements showed that hydrogen was completely evolved from the film at the on-set of crystallization when annealed at 800 °C. The edge of the reflectance fringes shifted to longer wavelength decrease in hydrogen content but shifted to shorter wavelength with increase in crystallinity.

Interface Effects Study in Hard–Soft Carbon Multilayered Films by AES Depth Profiling

Systems consisting of sequential layers of hard and soft carbon films were deposited on Si substrates by sputtering and plasma-assisted chemical vapor deposition (PACVD). A full characterization of the film and of the interfaces is considered crucial to obtain a correlation between the mechanical properties and the chemical composition and architecture of the films. In this work, the Auger-electron spectroscopy (AES) depth profiling technique was applied to study the chemical composition of the film and of the different interfaces (hard/soft layers; film/substrate). In particular, we focused on an optimization of the depth resolution parameters. A strong period–thickness effect on the film/substrate interface width was observed. Sputtering-induced roughness was also evaluated to check its effect on the interface width and on its morphological changes.

Structural and electrical properties of low resistance Pt/Pd/Au contact on p-GaN

We have investigated electrical and structural properties of Pt/Pd/Au ohmic contact on p-type GaN:Mg (2.5 × 1017 cm−3) using Auger electron spectroscopy (AES) and glancing angle x-ray diffraction (GXRD) analysis. It was shown that the specific contact resistivity improved with increasing annealing temperature. The annealing of the contact at 600∘C for 2 min in flowing N2 atmosphere resulted in a specific contact resistivity of 3.1 × 10−5 Ω cm2. Both GXRD and AES depth profile results show that Ga3Pt5, Ga2Pd5, and Au7Ga2 phases are formed at the interface region between metal and GaN when annealed at temperatures 600∘C. Possible explanation is suggested to describe the annealing dependence of the specific contact resistivity of the Pt/Pd/Au contacts.

Determination of the interdiffusion coefficient for the CdS/CdTe heteroestructure by AES sputter depth profiling

Abstract Double heterostructures were prepared by depositing CdTe films on stainless steel (ss) substrates by the close spaced sublimation (CSS) method. The CdTe films were treated with a saturated solution of CdCl 2 in methanol, dried in air and annealed at 400 °C. CdS layer of 0.2 μm was deposited on the CdTe film by the chemical bath method. The CdS/CdTe system was treated with saturated solution of CdCl 2 in methanol and annealed for 30 min in air at different temperatures from 300 to 400 °C. The samples were characterized by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES). The main effect of the temperature is to change the surface morphology of the CdS film from polycrystalline to an amorphous texture. By AES depth profiling the diffusion processes of the constituent element of the film was studied.

Investigation of Electroplating-Induced Degradation of PMZNT Relaxor Ferroelectrics

Resistance degradation of lead magnesium niobate-based (PMZNT) ceramics during nickel electroplating was investigated using resistivity measurement and auger electron spectroscopy (AES) analysis. It was found that the resistivity of the ceramics remained nearly unchanged at the initial stage of the electroplating, and, as electroplating time increased, the resistivity decreased rapidly. An AES depth profile analysis of a degraded specimen showed oxygen content in the surface to be lower than the theoretical value, and the relationship of oxygen content and detection depth was obtained. The results indicated that Pb 2+ and Nb 5+ were reduced to lower valence states and oxygen in the lattice was lost, thereby leading to a generation of oxygen vacancies. Hence, the conductivity of the dielectrics was enhanced. The results also indicated that only the outermost surface had suffered the reducing effect induced by hydrogen generated during nickel electroplating, whereas the bulk material remained impervious.

Thermal Stability of Spin Valves Incorporating New Amorphous ZrAl Alloy Films as Under and Capping Layers

We investigated the thermal stability and interdiffusion behavior of new amorphous ZrAl-based spin valves (SVs) and compared them with similarly structured Ta-based top (T) and bottom (B) SVs. The magneto-resistance (MR) ratios of ZrAl-based T-and B-SVs were enhanced from 8.49 to 9.14% and from 6.91 to 7.54%, respectively. The Ta-based SVs degraded relatively quickly at elevated temperatures because of interlayer diffusion. In contrast, the MR ratio of the ZrAl-based T-SV decreased by only 6.6% (9.14 /spl rarr/ 8.54%), while that of the B-SV increased by 2.3% (7.54 /spl rarr/ 7.71%), after annealing at 300/spl deg/C for 240 min. This result and the Auger electron spectroscopy (AES) depth profile clearly showed that ZrAl-based SVs have high interdiffusion resistance. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) analyses of the root-mean-square (rms) roughness indicated that the ZrAl layer (0.162 nm) has a smoother interface than the Ta layer (0.431 nm). The ZrAl-based SV has a fine, dense microstructure. It resists interdiffusion at elevated temperature and results in superior thermal stability over traditional Ta-based SVs.

Adhesion of rubber compounds to nano-copper-coated iron plates as studied by AES depth profiles

Three nano-copper-coated iron plates with different thicknesses of the copper coating from 29 to 56 nm were prepared by sputtering and their adhesion properties to rubber compounds were examined. At the optimum cure of rubber, the nano-copper-coated iron plate with thick copper coating (56 nm) showed the best adhesion to rubber compound, whereas the thin copper coating (29 nm) showed the best adhesion to rubber compound at overcure. This may be explained as follows: at optimum cure, diffusion of iron to the copper surface in the adhesion interphase is dominant, whereas copper sulfide formation in the adhesion interphase is dominant at overcure. This fact was confirmed by Auger electron spectroscopy (AES) depth profiles of adhesion interphases using Ar+ ion sputtering.

Improvement of electrical conductivity of Cu/Ag glue joints by discharge cleaning

A study of different methods for cleaning copper components to improve electrical conductivity of Cu/Ag glue joints is presented. Copper samples were cleaned with three different methods: (i) wet chemical cleaning with tetrachloroethylene, (ii) discharge cleaning with an oxygen plasma, and (iii) subsequent discharge cleaning with oxygen and hydrogen plasmas. Discharge cleaning was performed in a low-pressure weakly-ionized plasma created with a RF generator of the output power of 200 W and the frequency of 27.12 MHz. The concentration of impurities on the copper surface was determined by Auger electron spectroscopy (AES) depth profiling. Cleaning with oxygen plasma caused effective removal of organic impurities, but the oxygen concentration on the surface was increased. Additional cleaning with hydrogen plasma effectively reduced the oxide film, so the copper surface became virtually free of any impurities. The electrical resistance of the joints between the components treated by different methods showed that the contact resistance is decreased with increasing copper surface cleanliness.

Quantitative AES depth profiling of a Ge/Si multilayer structure

AbstractAuger electron spectroscopy (AES) depth profiling of a Ge/Si multilayer structure with Ge layers of 2.2, 4.3 and 2.2 nm thickness in Si was performed with Ar+ ions of 1.5 and 3 keV energy and at 74° incidence angle to the normal to the surface. The plot of the Ge LMM Auger peak intensity as a function of the sputtering time was analysed quantitatively using the MRI (mixing–roughness–information depth) model. As a result, the optimum MRI parameters w (mixing length), σ (roughness) and λ (here, used as information depth) were found to be 1.7, 0.8 and 1.6 nm, respectively, for 1.5 keV Ar+ bombardment. For an appropriate evaluation of the 3 keV Ar+ data, w had to be increased to 3.0 nm and σ to 1.4 nm, respectively, while λ was kept constant. In the first run, the MRI calculation results could not be fitted optimally to the profiling results, and therefore the assumed in‐depth distribution of Ge had to be changed accordingly. After a few modifications of the latter and of the roughness parameter, an optimized fit was obtained by changing either the thickness of the layers or the average Ge concentration within the layers, or, most favourably, by a combination of both approaches. Comparison with densitometer measurements on transmission electron microscopy images confirm the thicker layer structure. Copyright © 2002 John Wiley & Sons, Ltd.

A STUDY OF ALUMINA THIN FILMS GROWN BY LOW PRESSURE MOCVD: XPS AND AES

We have studied the chemical composition of alumina ( Al 2 O 3) films grown on Si(100) at different substrate temperatures by metalorganic chemical vapor deposition (MOCVD) using aluminium acetylactonate { Al(acac) 3} as the precursor. We have found that the resulting films of Al 2 O 3 contain substantial amounts of carbon. X-ray photoelectron spectroscopy (XPS) was employed to study the chemical state of carbon present in such films. The XPS spectrum reveals that the carbon present in Al 2 O 3 film is graphitic in nature. Auger electron spectroscopy (AES) was employed to study the distribution of carbon in the Al 2 O 3 films. The AES depth profile reveals that carbon is present throughout the film. The AES study on Al 2 O 3 films corroborates the XPS findings. An investigation of the Al 2 O 3/ Si (100) interface was carried out using cross-sectional transmission electron microscopy (XTEM). The TEM study reveals textured growth of alumina film on Si(100), with very fine grains of alumina embedded in an amorphous carbon-containing matrix.

Growth and characterization of silicon nitride films on various underlying materials

Characteristics of silicon nitride (SiNx:H) films, grown by plasma enhanced chemical vapor deposition (PECVD) on various metals such as Ta, IrMn, NiFe, Cu, and CoFe at various temperatures down to 100 °C, were studied using measurements of BHF etch rate, surface roughness and Auger electron spectroscopy (AES). The results were compared with those obtained for SiNx:H films on Si. The deposition rate of SiNx:H films increased slightly as deposition temperature decreased, and showed a weak dependence on the underlying materials. The surface of the nitride films deposited on all underlying materials at lower temperatures (below 150 °C) became rougher. In particular, a bubble-like surface was observed on the nitride film deposited on NiFe at 100 °C. At higher deposition temperatures (above 200 °C), SiNx:H films on all the above metals had small RMS values, except for films on Cu which cracked at 250 °C. BHF (10:1) etch rate increased dramatically for nitride films deposited below 150 °C. For different underlying films, the BHF etch rate was quite different, but exhibited the same trend with decrease in deposition temperature. AES measurements showed that Si and N concentrations in the SiNx:H films were only slightly different for the various deposition temperatures and underlying materials. AES depth profile of nitride films indicated that both surface O content and the depth of oxygen penetrating into SiNx:H increased for low temperature-deposited films. However, there was no observed oxygen signal from within the films, even for films deposited at 100 °C, and both Si and N concentrations were uniform throughout the film.

Interdiffusion in Exchange Biased NiFe/IrMn/CoFe Electrode in Magnetic Tunnel Junctions

ABSTRACTExtent of Mn diffusion to the plasma-oxidized AlOx tunnel barrier of magnetic tunnel junction was examined using Auger Electron Spectroscopy (AES) and X-Ray Photoelectron Spectroscopy (XPS). A magnetic film stack consisting of Ta/AlOx/CoFe/IrMn/NiFe/Ta was deposited with the AlOx layer treated under different plasma oxidation durations. AES depth profiles showed that Mn diffusion to the AlOx/CoFe interface increased with increasing oxidation after annealing at 300°C. XPS analysis indicated that Mn found at the CoFe/AlOx interface in the over-oxidized electrode was in the form of MnO2. Our research suggests that Mn diffusion was accelerated by preferential oxidation of Mn at the CoFe/AlOx interface.

Effects of surface structure on depth resolution of AES depth profiles of Ni/Cr multilayers

The influence of surface topography and crystalline structure on the depth resolution of Auger electron spectroscopy (AES) depth profiles of Ni/Cr multilayers was studied on three different samples sputter deposited onto smooth Si(111) substrates: an Ni/Cr multilayer composed of 16 alternating Ni and Cr layers with a single layer thickness of ∼30 nm, and the same Ni/Cr multilayer covered either with a smooth amorphous Ta 2 O 5 layer ∼50 nm thick or a crystalline Al layer with an average thickness of ∼40 nm and a relatively large average surface roughness (R a = 21.5 nm) in comparison with the first two samples (R a < I nm). All three types of samples were AES depth profiled with (1 rpm) and without sample rotation, using two symmetrically inclined 1 keV Ar + ion beams at two different ion incidence angles of 47° and 80°. The AES depth profiles obtained at an ion incidence angle of 47° on stationary Ni/Cr and a-Ta 2 O 5 /Ni/Cr multilayer samples with smooth surfaces showed sharp interfaces with a depth resolution of approximately the same order of magnitude. However, due to surface microroughness induced by ion sputtering, a slight monotonous degradation of the depth resolution with sputter depth was observed on both samples. In contrast, AES depth profiling of the Al/Ni/Cr stationary sample with the initially rough crystalline Al surface layer caused in-depth topographical changes of the Ni/Cr multilayer, and the originally sharp internal interfaces were strongly broadened. The optimal depth resolution was obtained by rotational depth profiling of the samples at an ion incidence angle of ∼80°, The values of depth resolution were independent of the sputter depth, and were of the same order of magnitude for all three types of samples, lying between 4.5 and 8.0 nm. An atomic force microscopy study of as-deposited and selected ion-sputtered samples showed that use of a grazing incidence angle and sample rotation during AES depth profiling promoted a smoothing effect and reduced the microroughness of the initially rough sample surface.