Rutherford Backscattering Spectrometry Results Research Articles

Efficiency of TiN diffusion barrier between Al and Si prepared by reactive evaporation and rapid thermal annealing

TiN layers prepared by reactive evaporation and rapid thermal annealing were tested as diffusion barrier between Al and Si. First, Rutherford backscattering spectroscopy (RBS) analysis of Al/Ti(N)/Ti/Si and Al/Ti(N)/Si multilayer structures showed that Si does not diffuse out up to a sintering temperature of 550 °C. However, as the temperature increases beyond 450 °C, Al starts to react with TiN. This reaction leaves less than half the TiN original thickness after a 30 min anneal at 550 °C. The RBS results indicate that TiN, crystallized at a temperature around 850 °C, forms a good barrier between Al and Si. Electrical measurements on various microelectronic devices were performed to verify this. Annealing of Ti(N) at 900 °C leads to a breakdown of p-MOS (metal–oxide–semiconductor) devices while n-MOS devices still work properly. Annealing at 800 °C gives good results on both MOS types except that the contact resistance of a p-type resistor is higher than desired. The electrical circuit failure is mainly due to dopant loss from the active area of the device into the titanium silicide which forms during the rapid thermal annealing at 800 or 900 °C of the deposited Ti(N) layers.

Nitrogen ion implantation into the amorphous CN films prepared with ion beam assisted deposition

In order to further increase the nitrogen content of the amorphous CN films prepared with ion beam assisted deposition (IBAD), nitrogen ion implantation at 50 keV has been performed with the films. The films were characterized by Auger electron spectroscopy (AES), Rutherford backscattering spectrometry (RBS), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Both AES and RBS results show that the N concentration of the implanted films can be increased up to a saturated value of about 43 at.%. Although this saturated value is still lower than the stoichiometric N concentration of β-C 3N 4, TEM observation indicates that crystalline β-C 3N 4 with a dimension of about 30 nm has been grown at a dose of 10 18 ions cm −2. It is also demonstrated by XPS that nitrogen ion implantation can result in more sp 3 bonding character in the CN films.

Preparation, structure, composition, optical and photoelectrochemical properties of vacuum annealed In-Se thin films

In2Se3 thin films have been prepared by sequentially evaporating In and Se followed by vacuum annealing at different temperatures. X-ray diffraction studies of the annealed films indicate the presence of β-In2Se3 along with free Se in the deposit. Rutherford backscattering spectrometry (RBS) analysis gave the In to Se ratio as 0.676 but it changed with annealing temperature. Proton-induced X-ray emission (PIXE) analysis of the annealed films gave an In to Se ratio lower than that of the RBS value. The discrepancy in the RBS and PIXE results has been discussed in terms of the inhomogeneity present in the In-Se film. The (KβKα) X-ray intensity ratios of In and Se in In-Se film have been estimated and found to be lower than their respective elemental values. The results have been attributed to the chemical/environmental changes in the electronic structure of In-Se films. The band gap has been estimated from the optical absorption studies and found to be ∼ 1.8 eV but changes with annealing temperature. A film formation mechanism involving the reaction between In and Se under thermal treatment has been described. Finally, photoelectrochemical solar cells have been fabricated and the results are discussed.

Preparation, structure, composition, optical and photoelectrochemical properties of vacuum annealed In-Se thin films

In 2 Se 3 thin films have been prepared by sequentially evaporating In and Se followed by vacuum annealing at different temperatures. X-ray diffraction studies of the annealed films indicate the presence of β-In 2 Se 3 along with free Se in the deposit. Rutherford backscattering spectrometry (RBS) analysis gave the In to Se ratio as 0.676 but it changed with annealing temperature. Proton-induced X-ray emission (PIXE) analysis of the annealed films gave an In to Se ratio lower than that of the RBS value. The discrepancy in the RBS and PIXE results has been discussed in terms of the inhomogeneity present in the In-Se film. The (K β K α ) X-ray intensity ratios of In and Se in In-Se film have been estimated and found to be lower than their respective elemental values. The results have been attributed to the chemical/environmental changes in the electronic structure of In-Se films. The band gap has been estimated from the optical absorption studies and found to be ∼ 1.8 eV but changes with annealing temperature. A film formation mechanism involving the reaction between In and Se under thermal treatment has been described. Finally, photoelectrochemical solar cells have been fabricated and the results are discussed.

Determination of P/Al ratio in phosphorus-doped aluminium oxide thin films by XRF, RBS and FTIR

Phosphorus-doped aluminium oxide thin films were deposited in a flow-type ALE reactor from AlCl3, H2O and from either P2O5 or trimethyl-phosphate. Structural information of the films was obtained from Fourier transform infrared (FTIR) spectra. Rutherford backscattering spectroscopy (RBS) was used to quantitatively determine the composition of the films. The P/Al intensity ratios calculated from X-ray fluorescence (XRF) results were in a linear relation with the P/Al concentration ratios calculated from RBS results. For comparison, the intensity ratios of the phosphorus peak (P=O) at about 1250 cm−1 and the aluminium peak (Al-O) at about 950 cm−1 were determined from the IR absorption spectra. The calibration of FTIR peak intensities was done by plotting the intensity ratios of phosphorus and aluminium peaks against the P/Al concentration ratios measured by RBS. FTIR gave also a linear calibration curve with RBS but the method is less suitable for routine analysis of P/Al ratio than XRF.

Rutherford Backscattering Studies of Polypyrrole Films: I . Effect of Electrolyte on Deposition Efficiency

The effect of three different electrolytes on the efficiency of polypyrrole deposition was studied using Rutherford backscattering spectrometry (RBS). The RBS results were used to determine the thickness, roughness, and composition of the polypyrrole films. The films were deposited from aqueous solutions of sodium perchlorate, sodium xylene‐sulfonate, and poly(sodium 4‐styrene‐sulfonate) (NaPSS). The highest deposition efficiency (93%) was obtained with the sodium xylene‐sulfonate electrolyte. The NaPSS electrolyte yielded the highest film density and the lowest film roughness. Deposition from electrolytes yielded the lowest efficiency and the roughest films. Evidence for a nucleation and growth mechanism was also observed.

Diamond-Like Coatings : Microstructural Evolution under Ion Beam Assistance

Non-hydrogenated diamond-like carbon films have been prepared by Dual Ion Beam Sputtering and Ion Beam Assisted Magnetron. The assistance parameters -ion energy, ion mass, ion flux/atom flux-have been systematically varied and their effect on the microsaucture of the films studied. The films have been characterised by Rutherford Backscattering Spectroscopy (RBS), High Resolution Transmission Electron Microscopy (HRTEM), Electron Energy Loss Spectroscopy (EELS), Positron Annihilation Spectroscopy (PAS), and Raman Spectroscopy (RS). RBS and PAS results showed that the density and the degree of disorder of the films go through a maximum with ion energy, and that the void concentration goes through a minimum. EELS and RS show that the films are mostly sp 2 bonded, with a maximum concentration of sp 3 bonding of about 16% for the largest values of density. The evolution of density with ion flux and energy is consistent with a combined effect of atomic displacements in the film leading to densification, and with damage buildup leading to progressive graphitisation as the energy is increased

Study of the relation between composition and physical properties of YBaCuO thin films using RBS, NRA, XRD, XAS and ϱ( T)

Superconducting YBaCuO thin films with various oxygen contents were prepared by inverted cylindrical magnetron sputtering of a stoichiometric YBaCuO target on a MgO single crystal heated to about 750°C. The samples were cooled to room temperature either (i) at p o 2 = 0.25 mbar or (ii) at p o 2 = 1 atm.As-grown samples were characterized by ϱ( T) measurements ( T c, Δ T c). The film composition was determined by Rutherford backscattering spectrometry (RBS) in random and channeling geometries, nuclear reaction analysis (NRA) and X-ray diffraction (XRD). The oxygen content, directly measured by RBS and NRA, were compared to that deduced from the c-axis lattice parameter. While for the (i) samples a difference is observed between RBS and XRD results, the latter being inconsistent with both T c and the oxygen content, for the (ii) samples, a good agreement is found. The copper oxidation state was controlled by X-ray absorption spectroscopy (XAS) of the CuL 2,3 edge operated in the total electron yield mode. The results show that for the as-grown YBaCuO films only the Cu(II) state is present. The effect of long temperature annealings in 18O 2 and 16O 2 atmospheres ( T = 650°C, t = 19 h) was also studied. The results are discussed.

Quantitative thin‐film analysis with an energy‐dispersive x‐ray detector

AbstractRecent mathematical approximations of ϕ(ρz), the depth distribution of electron‐excited x‐rays, have opened up the possibility of accurate quantitative analysis of thin‐film specimens by electron beam techniques. This method has been used extensively in electron probe microanalysis. This paper demonstrates quantitative analyses of thin films using energy‐dispersive x‐ray analysis (EDS) coupled with the ϕ(ρz) method. Metal and oxide films were analyzed by several techniques, including electron probe microanalysis (EPMA), Rutherford backscattering spectroscopy (RBS), x‐ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), spectroscopic ellipsometry (SE) and x‐ray fluorescence spectroscopy (XRF); the results were compared with those obtained from the EDS thin‐film analysis. In the case of Al2O3 films, EDS film thickness results agree to within ±4%, ±7% and ±9% of the TEM, EPMA and SE results, respectively. For metal films, the EDS results agree to within ±12% (thicknesses) and ±7% (composition) of the RBS, EPMA and XRF results.

Interface study of physically vapour-deposited TiN coatings on plasma-nitrided tool steel surfaces with Auger electron spectroscopy, resonant nuclear reaction analysis and Rutherford backscattering spectroscopy

It is known that adhesion of a TiN coating on a plasma-nitrided tool steel surface depends strongly on the kind of substrate material and on the process steps between plasma nitriding and deposition of TiN. To obtain relevant information concerning the interface composition a combined Auger electron spectroscopy (AES), resonant nuclear reaction analysis (RNRA) and Rutherford backscattering spectroscopy (RBS) analysis has been performed. With these techniques, mutually complementary information could be obtained by measuring quantitative nitrogen (RNRA) and qualitative nitrogen, titanium and iron depth profiles (AES). The composition of the interface between the TiN coating and the plasma-nitrided surface was deduced from both AES and RBS results. The results indicate that the transition treatment carried out between plasma nitriding and TiN coating influences the interface composition. They will be explained in relation to previous adhesion results. The work was carried out on high speed steel ASP 23 and on cold-worked steel 1.2379.

Ar+-induced mixing mechanisms in metal-metal bilayer systems

Ion-beam mixing in Al-Pd, Al-Cr, Pd-Cu, Ag-Cu and Ag-Fe bilayers has been studied using Rutherford backscattering spectroscopy (RBS) and Auger electron spectroscopy (AES) over an ion dose range between 1 × 1015 and 1 × 1016 Ar+ cm−2 at room temperature. RBS and AES results show that the mixing efficiency of the light elements is higher than that of the heavy elements. The mixing efficiency of a heavy element is independent of the heat of mixing energy, while that of a light element has a close relation with the heat of mixing. The experimental results are discussed in terms of cascade mixing and thermal spike mixing.

Effects of Processing Parameters on KrF Excimer Laser Ablation Deposited ZrO2 Films

ABSTRACTSystematic experiments have been carried out to characterize the yttria containing zirconia thin films on sapphire substrates by 248nm KrF excimer laser ablation. The deposition rate as a function of laser fluence and O2 pressure at room temperature was measured with a quartz crystal microbalance. The results show different threshold fluences for deposition in vacuum vs. oxygen. While the deposition rate increases with increasing fluence at a given oxygen pressure, the rate eventually saturates at a higher laser fluence. At a given fluence, the oxygen pressure dependence of the deposition rate shows a radical reduction when the O2 pressure increases from 10 mTorr to 1 Torr. Rutherford backscattering spectrometry (RBS) and x-ray photoelectron spectroscopy were used to obtain stoichiometric information. A very strong pressure dependence of the O/Zr ratio was observed. While the trend of increasing O/Zr and Zr/Y ratio with increasing O2 pressure is apparent, the correlations between O/Zr as well as Zr/Y ratio and other processing conditions are less obvious. RBS results indicate an increasing roughness at the interface between the ZrO2 film and the sapphire substrate as the oxygen pressure exceeds 50 mTorr. The structural information obtained from x-ray diffraction patterns indicates broadening of peak width with increasing laser fluence as well as decreasing substrate temperature. For the film deposited at a lower substrate temperature, a strong (002) texture was observed.

Effects of Processing Parameters on KrF Excimer Laser Ablation Deposited ZrO2 Films

AbstractSystematic experiments have been carried out to characterize the yttria containing zirconia thin films on sapphire substrates by 248nm KrF excimer laser ablation. The deposition rate as a function of laser fluence and O2 pressure at room temperature was measured with a quartz crystal microbalance. The results show different threshold fluences for deposition in vacuum vs. oxygen. While the deposition rate increases with increasing fluence at a given oxygen pressure, the rate eventually saturates at a higher laser fluence. At a given fluence, the oxygen pressure dependence of the deposition rate shows a radical reduction when the O2 pressure increases from 10 mTorr to 1 Torr. Rutherford backscattering spectrometry (RBS) and x-ray photoelectron spectroscopy were used to obtain stoichiometric information. A very strong pressure dependence of the O/Zr ratio was observed. While the trend of increasing O/Zr and Zr/Y ratio with increasing O2 pressure is apparent, the correlations between O/Zr as well as Zr/Y ratio and other processing conditions are less obvious. RBS results indicate an increasing roughness at the interface between the ZrO2 film and the sapphire substrate as the oxygen pressure exceeds 50 mTorr. The structural information obtained from x-ray diffraction patterns indicates broadening of peak width with increasing laser fluence as well as decreasing substrate temperature. For the film deposited at a lower substrate temperature, a strong (002) texture was observed.

Rutherford backscattering spectroscopy and X-ray photoelectron spectroscopy studies of thin glass films prepared by laser evaporation

Multicomponent glass and laser-evaporated thin films prepared from the glass were studied by Rutherford backscattering spectroscopy (RBS) and X-ray photoelectron spectroscopy. The composition of the glass and the film as determined through RBS suggested that the films were deficient in oxygen. Furthermore, an increase in the reduced states of vanadium ions in going from the glass to the film was detected from the shift in the binding energy of the core level peak of V 2p and the development of a component peak in the V L 3M 23V Auger spectra. The reduction of vanadium could have possibly occurred because of the loss of oxygen during evaporation and thus would support the RBS results.

Dopant Site Location in Dual-Implanted Gap using {111} Planar Channeling

ABSTRACTPrevious studies have indicated that dual implantation can efficiently introduce group IV dopant onto selected sub-lattice sites in m-V compound semiconductors, thus enhancing electrical activation. We studied this phenomenon in GaP using Rutherford Backscattering Spectroscopy (RBS) to determine the lattice location of Sn atoms. We used single crystals of GaP (100) which had been implanted at 400° C with120 Sn+ following previously implanted69 Ga+ or 31P+. Energies were selected for euivalent projected ranges, and all species were implanted with doses of 1 × 1015 atoms/cm2 . Asymmetry in the angular scan of the {111} planar channel was then used to determine the sub-lattice location of the implanted Sn. RBS results indicated that for all implants Sn atoms were substituting Ga and P sites eually. However, Hall effect measurements gave p type conduction for GaP implanted with Sn alone, while those with prior implants of Ga or P resulted in n-type conduction. RBS and Hall effect results are explained by a vacancy complex model.

Organometallic chemical vapor phase deposition of “Mn 2Si”

We have deposited Mn 2Si films on nickel foils by the pyrolysis of the organometallic complex Mn 2(CO) 10(μ-SiH 2). These films have been subsequently studied by Rutherford backscattering spectrometry (RBS) and are observed to be isotropic. Scanning electron microscopy and X-ray diffraction indicate that the deposition rate is rapid and results in the formation of amorphous films. The RBS results, as well as depth profiling using Auger electron spectroscopy, demonstrate that the films formed by the vapor phase pyrolysis of this metal carbonyl silyl complex have a stoichiometric ratio of manganese to silicon that is well preserved at 2:1 for substrate deposition temperatures above 300°C.

Characterization of titanium nitride films sputter deposited from a high-purity titanium nitride target

Titanium nitride films (100–300 nm) were sputter deposited from a high-purity titanium nitride target (nominal purity 99.99%) in an experimental dc-magnetron system. The gold-colored target, 5 cm in diameter, had a density of 92% of the theoretical value. X-ray diffraction indicated that the target material matched the simulated stoichiometric TiN pattern, while the deposited films showed a shift in the crystallographic plane spacing of the (111) and (200) Bragg reflections. Rutherford backscattering spectrometry (RBS) performed on titanium nitride films which were deposited on amorphous carbon substrates indicated the presence of titanium, nitrogen, and oxygen as principal components of the films. No argon was detected in the films within the sensitivity of the RBS technique. Titanium to nitrogen atomic ratios in the films varied from 0.83 to 1.02 according to the RBS results. The binding energy measured by x-ray photoelectron spectrometry (XPS) indicated that Ti and N were present in compound form. The effect of substrate temperature deposition, dc bias, and nitrogen content in the sputtering gas were correlated to the stoichiometry and resistivity of the films. High rates of deposition (3.8 nm/s) on hot Si(100) substrates produced films with a resistivity as low as 40 μΩ cm. The performance of the TiN films as a diffusion barrier was evaluated in a Al/TiN/TiSi2/Si(100) layered structure.

Thermal stability of WSix/GaAs interface

Secondary ion mass spectrometry (SIMS), Rutherford backscattering spectrometry (RBS), and measurements of forward current-voltage characteristics at various temperatures were used to study metallurgical reactions in WSix/GaAs formed by sputter deposition. Both SIMS and RBS showed that annealing at 800 °C results in migration of W and Si into GaAs when the atomic ratio x deviates from 0.5. On the other hand, the forward current-voltage characteristics of WSix/GaAs diodes at various temperatures showed that the excess current across the interface induced after annealing is large when x deviates substantially from 0.5, in agreement with the SIMS and RBS results. It is suggested that the migration of W and Si is directly involved in the thermal degradation of the structural and electrical properties of the WSix/GaAs interface and its x dependence.

In situ rutherford backscattering spectroscopy for electrochemical interphase analysis

For the first time, Rutherford backscattering spectroscopy (RBS) has been used for in situ monitoring of the electrochemical interface. A thin membrane (itd ∼ 1.5 μ) was used as a window for the electrochemical cell, separating the liquid electrolyte from the vacuum of the beam line. The working electrode is evaporated onto the backside of the membrane. The design of the electrochemical cell for in situ RBS and first preliminary results for copper deposition onto iridium and oxide formation on titanium are presented. The power and the limits of this new RBS application are briefly discussed.

SIMS depth profiling of multilayer metal-oxide thin films — improved accuracy using a xenon primary ion

Multilayer thin films containing silver and copper, sandwiched in a metal oxide, have been depth profiled by secondary ion mass spectrometry (SIMS) using primary ions of differing mass, energy and chemical reactivity. These results were compared for accuracy with those obtained by Rutherford backscattering spectrometry (RBS). The use of O 2 + or O − as primary ions resulted in severe distortion of the silver ion intensity distribution in the SIMS profile of a ZnO/Ag/ZnO thin film on glass; O 2 + bombardment at energies from 3–10 keV resulted in the detection of silver at the glass interface, while the use of O − caused the silver to be detected closer to the outer surface than expected from RBS results. Primary beams of Ar + and Xe + gave progressively more accurate results for the Zn/Ag/Zn distribution; Xe + at 5.0 keV energy produced profiles that agreed within 10% of RBS-derived values. The same beam conditions, used to profile a double silver layer in ZnO, resulted in some discrepancy in the position of the inner layer, compared to RBS results, and this was attributed to an enhanced sputter rate in the oxide under the outside metal film. Depth profiling of TiO 2/Cu/TiO 2 films with oxygen also resulted in significant distortion of the perceived position of the metal layer, and this was again significantly improved using Xe + primary ions of 6–9 keV energy. The distorting effects of oxygen bombardment can be understood in terms of a migration of metal ions in an electrostatic field created by a charged surface. Ionization of the metallic layer is enhanced by the use of oxygen. By contrast, the use of rare gases reduces the production of ions from the metallic layer which can migrate prior to the onset of sputtering.