Papers

ICMCTF2004 Session FP: Symposium F Poster Session

Thursday, April 22, 2004 5:00 PM in Room San Diego

Thursday Afternoon

Time Period ThP Sessions | Topic F Sessions | Time Periods | Topics | ICMCTF2004 Schedule

FP-2 Investigations of the Dependence of Secondary Electron Emission Coefficient γ on Surface-morphology of Mgo Thin Films A.I. Ide-Ektessabi, Y.M. Morimoto, H.N. Nomura (Kyoto University, Japan); Y. Tanaka (Mitsubishi Materials Kobe Tools Corporation, Japan); S.M. Murakami, K.T. Tojo, N.Y. Yasui (Kyoto University, Japan) Thin film of MgO is widely used as a protecting layer of plasma display panel (PDP). The dependence of secondary electron emission coefficient γ on surface-morphology of MgO thin films was investigated. The MgO thin films ware prepared using electron beam evaporation (EB) and ion beam-assisted deposition (IBAD). On preparing MgO thin films, deposition rate, annealing condition, and current density of ion beam were changed. Surface-morphology was measured with Atomic Force Microscope (AFM), and the secondary electron emission coefficient γ was measured using an electrostatic electron energy-current analyzer. The density, the crystallinity, and the surface contamination were also measured using Rutherford Backscttering Spectrometry (RBS), X-Ray Diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), respectively. Experimental results suggest that the surface-morphology strongly influences the secondary electron emission coefficient γ.
FP-3 Electrical Properties and Crystal Structure of Nitrogen Doped Ge₂Sb₂Te₅ Thin Film for Phase Change Memory S.M. Kim, M.J. Shin, D.J. Choi (Yonsei University, South Korea); K.N. Lee, S.K. Hong, Y.J. Park (Hynix Semiconductor Inc., South Korea) The Ge₂Sb₂Te₅ thin film is one of the attractive candidates for phase change memory using the difference of electrical properties between amorphous and crystalline state. In this study, the characteristics of nitrogen doped Ge₂Sb₂Te₅ thin films deposited on Si (100) substrate were investigated by X-ray diffraction (XRD) analysis, four-point probe and atomic force microscopy (AFM). The nitrogen contents of the films were controlled by changing the ratio of N₂ to Ar gas flow rates, while the total flow rates were fixed to 40sccm. It was found that the sheet resistance (Rs) of the films annealed at 260°C increased and the fcc peaks of crystalline state of the films gradually disappeared with the increase of nitrogen concentration. At the N₂ flow rate of 12sccm, however, the sheet resistance of the film remarkably dropped around to that of crystalline state of undoped film and the crystal structure was transformed from fcc to hexagonal. In the next study, we will examine the electrical properties of the nitrogen doped Ge₂Sb₂Te₅ thin film deposited on other substrates (TiN/Si, SiO₂/Si).
FP-4 Effect of Heat Treatment under Controlled Atmosphere on the Properties of TiN Film Deposited by Unbalanced Magnetron Sputtering G.P. Yu (National Tsing Hua University, Hsinchu, Taiwan, R.O.C.); K.J. Yu (Chip Sense Corp., Taiwan, R.O.C.); J.H. Huang (National Tsing Hua University Taiwan R.O.C.) Heat treatment processes were widely applied to enhance the characteristics of TiN thin films. TiN films were deposited on Si wafer using an unbalanced magnetron sputtering technique. Heat-treated environment, including air, Ar/H₂, and Ti getter were discussed with thermodynamic and kinetic analysis. The specimens were heat-treated at 500 and 700°C for 1 hour under optimal atmosphere to reduce the oxidation of the thin films. After heat treatment, the microstructure, resistivity and packing factor of the TiN thin films were not significantly changed. However, the surface grain size was enlarged and crystallization improved. The (200) preferred orientation was more distinct at 700°C than 500°C with thinner thickness. (111) texture coefficient was enhanced at both heat-treated temperature. The hardness and roughness of the specimens after annealing were slightly degraded compared with as-deposited sample. This could be attributed to the relaxation of defect structures, about 40% at 500°C and almost 100% at 700°C. The residual stress of the specimens after 700 heat-treated was transformed from compressive to tensile stress that could be due to the smaller thermal expansive coefficient of Si substrate.
FP-5 Optical and Microstructure Characterization of Ta₂O_5-x Thin Films Deposited on the PET Substrate by RF Magnetron Sputtering Y.H. Pai, C.J. Lu (National Chung Hsing University, Taiwan, R.O.C.); C.C. Wang (National Chung Hsing University, Taiwan, R.O.C>); F.S. Shieu (National Chung Hsing University, Taiwan, R.O.C.) Optical properties and microstructure of Ta₂O₅-x thin films deposited on (100) Si and PET substrates by rf magnetron sputtering with different oxygen mixture ratios ranging from 37% ~ 55%, were investigated by UV/VIS photo spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM). It is obtained that the Ta₂O₅-x films produced with an oxygen mixture ratio 55% have optical transmission 70% in the visible range and band gap energy 3.7 eV. Transmission electron micrograph shows that the Ta₂O₅-x films consist of a mixture of nanocrystalline and amorphous phases with dense microstructure. Both SEM and AFM results show the coating surface is relatively smooth, and the thickness is uniform. In addition, SEM result reveals that the substrate has a pronounced effect on the microstructure of the Ta₂O₅-x films.
FP-6 Characterization and Applications of ZrN_x Thin Films Prepared by Dual Ion Beam Sputtering C.J. Lu, C.C. Wang, Y.H. Pai, F.S. Shieu (National Chung Hsing University, Taiwan, R.O.C.) Copper (Cu) is being used as interconnects to replace aluminum (Al) in advanced ULSI technology because of its low electric resistivity and good electromigration resistance. One key issue remains to be solved is to find a good diffusion barrier material to suppress interdiffusion between Cu and Si substrate. Zirconium nitride (ZrN) exhibits good thermal and chemical stabilities, high melting point and hardness, and good corrosion resistance. As a result, it has been considered to be a potential material for the application in ULSI technology. In this study, ZrN thin films were deposited on Si substrate by a dual ion beam sputtering (DIBS) system. Two process parameters, i.e., Ar gas flow rate and ion beam current, were manipulated during deposition. Thickness measurement of the coatings by Î±-Step and atomic force microscopy (AFM) show that high Ar gas flow rate and Kaufman ion gun current increase the deposition rate. The surface of the ZrN coatings is rather smooth with an average roughness, Ra, less than 1 nm. Transmission electron microscopy (TEM) indicates that the ZrN films consist of nanocrystalline grains of size about 1~7 nm. The films also exhibit (111) preferred orientation as revealed by grazing incident angle X-ray diffraction (GIAXD). Chemical analyses both by Rutherford backscattering spectrometry (RBS) and Auger electron spectroscopy (AES), show that the coating has a composition ZrNX with 1.5 < x < 2.0 , i.e., nitrogen rich. Evaluation of the barrier property of the coating was carried out by annealing of the multilayered samples Cu/ZrN/Si in vacuum at elevated temperatures, and then characterized by AES and secondary ion mass spectrometry (SIMS). The result shows that the ZrN films could prohibit interdiffusion between Cu and Si upon to 700°C. key word:IBAD, microstructure, nanocrystalline, diffusion barrier.
FP-7 Plasma Diagnostics on Synthesis Mechanism of Chromium Nitride Coatings by Unbalanced Magnetron Sputtering Process C.L. Chang, J.Y. Jao (Mingdao University, Taiwan, R.O.C.) Chromium nitrides (CrN) possess excellent mechanical, tribological and wetting characteristics for precision forming and molding applications. In this study, CrN coatings were deposited by unbalanced magnetron sputtering process. The reaction mechanism, including nitrogen dissociation, metal ionization, and chromium nitride deposition was examined by plasma diagnostics techniques. A Langmuir probe was used to analyze the plasma potential, ion density, electron temperature, and electron energy distribution. A quadrupole mass spectrometer was employed to analyze the mass spectra of neutrals, radicals as well as positive and negative ions. An optical emission spectrometer was installed to monitor the density of ionic species. The diagnostics provides a clear insight into the correlation between deposition parameters and CrN properties. Accordingly, the further modification of CrN films such as stress reduction, hardness enhancement, and microstructure evolution via plasma alteration can be based upon.
FP-8 X-ray Scattering Study in Homoepitaxial Growth of Sputter-deposited SrTiO₃ Films H.Y. Lee (National Synchrotron Radiation Research Center, Taiwan, R.O.C.); Y.W. Hsieh (National Synchrotron Radiation Research Center); C.-H. Hsu, K.S. Liang (National Synchrotron Radiation Research Center, Taiwan, R.O.C.) X-ray reflectivity and grazing incidence x-ray diffraction measurements were employed to characterize the microstructure of homoepitaxial SrTiO₃ (STO) films deposited on polished SrTiO₃ (001) substrates by radio frequency magnetron sputtering technique. The presence of oscillation fringe in the diffuse scattering indicates that the conformal relationship exist between layers and substrate in high temperature deposition. The appearance of interference fringes of the crystal truncation rod observed at the film grown higher than 750°C, clearly demonstrates the well epitaxial relationship between film and substrate.
FP-9 Anti-bacterial Silver Coatings Deposited on Activated Carbon Fibers by Unbalanced Magnetron Sputtering Process D.Y. Wang, W.L. Lo (Mingdao University, Taiwan, R.O.C.) Anti-bacteria silver coatings were deposited on activated carbon fibers by using an unbalanced magnetron sputtering process. The anti-bacteria activity depends on the existence of the silver cation (Ag⁺), which binds strongly to electron donor groups on biological molecules containing oxygen, sulfur, or nitrogen. The application of the unbalanced magnetron in conjunction with the pulsed DC bias results in a low temperature deposition of silver at 100-200°C. The bias voltage and argon partial pressure were used to control the microstructure, adhesion, and density of silver coatings. The anti-bacteria silver coating was characterized by field emission SEM, EDS, XRD as well as the bactericidal tests. The effectiveness of anti-bacterial silver coatings depends strongly on the particle size distribution and the mechanical integrity of the film.
FP-10 The Influence of Thermal Treatment on The Microstructure and Hardness in Eletroless Ni-P-W Deposit Y.I. Chen (E-Pin Optical Industry Co., Ltd., Taiwan, R.O.C.); S.K. Tien, J.G. Duh (National Tsing Hua University, Taiwan, R.O.C.) Ni-P-W alloy deposit on the mild steel substrate was obtained by the electroless process. Various thermal heat-treated temperatures from 350 to 600°C for 4 h were performed on the coating to evaluate the effect of crystallization behavior and grain size on the mechanical properties. The microstructure at as-deposited and heat-treated states was investigated by the X-ray diffraction (XRD) and transmission electron microscope (TEM). The hardness at all depths of the coating on the substrate could be acquired by the nanoindentation continuous stiffness measurement (CSM). The Ni-P-W coating showed an amorphous structure in the as-deposited state and exhibited a relatively low hardness of approximately 520HK. Under various heat treated temperature, the Ni-P-W coating hardness showed a maximum value of 1460HK at 500°C with the grain size around 40nm. After further heating up to 600°C, the strength decreased significantly and due to the grain coarsening.
FP-11 Plasma Diagnosis on CrN Films Synthesized by a Magnetically Controlled Cathodic Arc Evaporation Process D.Y. Wang, C.Y. Hung (Mingdao University, Taiwan, R.O.C.) In the presence of a transverse external magnetic field, the motion, including the direction and velocity, of arc spots can be controlled during the cathodic arc evaporation process. The generation of macroparticles in the deposited films can be suppressed with a modulated magnetic field and a direct injection of reactive gases. The influence of the magnetic field configuration on the plasma characteristic was studied by using the Langmuir probe and quodrupole mass spectroscopy. Plasma parameters such as plasma and floating potentials (Vp and Vf), electron temperature (Te), and the densities of ions and electrons (ni and ne) of the CrN plasma were measured. The tribological and microstructual analysis of the as-deposited CrN films were conducted by using an atomic force microscope, field emission microscope, and x-ray diffractometer. Properties of CrN films were correlated with the results from the plasma diagnosis of the CrN plasma.
FP-12 The Effect of Electroless Nickel Interlayer on the Corrosion Behaviors of CrN Coated Alloy Evaluated by Electrochemical Atomic Force Microscope J.W. Lee (Tung Nan Institute of Technology, Taiwan, R.O.C.); P.T. Chen, H.K. Chen, J.G. Duh (National Tsing Hua University, Taiwan, R.O.C.) Electrochemical atomic force microscopy (ECAFM) has become a useful tool to study the surface properties and reactions of corrosion down to atomic scale. With the aid of electrochemical control, detailed surface morphology changes can be in-situ observed during corrosion test. In this study, corrosion behaviors of the chromium nitride coated Fe-Mn-Al alloys with and without electroless nickel interlayer in the sodium chloride aqueous solution were investigated by the ECAFM. In-situ localized corrosion images were observed on the thin film surface. Traditional electrochemical tests were also used as a comparison. Scanning electron microscopy and electron probe microanalyzer were conducted to explore the chemical composition variations around corrosion pits. The correlation between surface defects and corrosion pits of the chromium nitride film were discussed. It was found that the macroparticles and pinholes were detrimental to the corrosion resistance of CrN film. The corrosion resistance of CrN film was enhanced by the presence of electroless nickel interlayer due to the restriction of sodium chloride electrolyte penetrating through the surface defects.
FP-13 Role of hcp-AlN on the Hardness Behaviour of Ti_1-xAl_xN Nanocomposites during Annealing A. Escudiero-Santana, A. Karimi (Swiss Federal Institute of Technology (EPFL), Switzerland); A. Schuetze, V.H. Derflinger (Balzers AG, Liechtenstein) TiAlN-based thin films are used to improve performance of cutting tools and hence are exposed to high-localized temperatures and high stresses which can activate mechanisms absent at room temperatures. Also, retention of hardness at high temperature is necessary for resistance against abrasive wear during machining. In this optic, systematic thermal treatments up to 1000°C were conducted on TiAlN thin films under controlled conditions. The films were deposited onto the tungsten carbide substrates using arc plasma, and the ration of Al/Ti was varied between 0.3 - 0.7. In this paper we first present the thermally induced structural modifications using HRTEM together with local chemical analysis. Then mechanical properties measured using depth sensing nanoindentation techniques together with fracture modes and mechanisms will be presented. Addition of Al favours structure refinement in these nitrides and beyond a certain concentration a nanocomposite AlTiN structure made of AlN and TiAlN are formed. It was found that Ti-rich films behave differently from Al-rich films under the same thermal conditions. If hardness of TiAlN films decreases with annealing, that of AlTiN films remains constant and even increases. Different mechanisms at the origin of this difference including phase transformation, thermal expansion, oxygen diffusion at the boundaries will be discussed.
FP-14 Chromium Nitride Coatings Deposited by Reactive Unbalanced Magnetron Sputtering: Influence of the Ion Energy and Ion Fluxes. J.J. Olaya, S.E. Rodil, E. Sanchez, S. Muhl (UNAM, Mexico) Increasingly chromium nitride (CrN) coatings are being used as a replacement for the titanium nitride coatings and electroplated hard chromium in various applications. This work reports an investigation of chromium nitride coatings deposited using unbalanced magnetron sputtering (UBM). Samples of CrNx were deposited at different ion energies and ion-current densities. Other deposition conditions, such as, substrate temperature, pressure and current density were kept constant. The microstructure and composition were analyzed by means X-ray diffraction (XRD) analyses, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. Ion current densities as a function of the target-substrate distance were evaluated by means of a planar Langmuir probe. The films were mostly stoichiometric, presenting a Cr:N ratio close to 0.5 The ion energy influenced primarily the crystal orientation and hardness. Films deposited without bias presented about 80% of (200) orientation and 20% (111), whereas at 100 V r.f bias the orientation was preferentially (200). Hardness values on stainless steel substrates varied from 1200 to 1600 HV0.01. Cross-section SEM pictures showed that the CrN films have a dense microstructure where columnar growth was inhibited. The relationship between growth conditions, microstructure and plasma parameters will be presented and discussed.
FP-15 Electromechanical Characteristics of Micromachined Self Actuating PZT Cantilever G.Y Kang, H.H. Park (Yonsei University, South Korea); T.S. Kim (KIST, South Korea) Recently, self-actuating cantilevers have been studied using piezoelectric films for high speed atomic force microscopy (AFM), scanning probe lithography, and high density data storage. Lead zirconate-titanate (PZT), boron-doped diamond, and oxidized zinc (ZnO) are the key materials for actuating the micro-electromechanical system. In this study, various sized PZT(Zr/Ti=52/48) cantilevers were fabricated to investigate the possible application of this piezoelectric film to micromechanical systems. The structure of micromachined PZT cantilever was Pt/PZT/Pt/Ta/SiO₂/SiNx/Si. PZT films with 500 nm-thick were prepared by sol-gel and hybrid method, i.e., sol-gel deposition of 100 nm thick PZT after sputter-deposited 400 nm thick PZT successively. PZT film was patterned by wet etching. Backside silicon was selectively removed after anisotropic etching in 20% TMAH solution. Electromechanical characteristics of micromachined PZT cantilever were measured by laser doppler vibrometer system as a function of cantilever length. The primary resonance frequencies and deflections of PZT cantilever with 200 um-width were proportional to length^-2 and length², respectively. The primary resonance frequencies of cantilever with 400, 600, 800, 1000, and 1200 um-length PZT cantilever prepared by sol-gel method were 14.5, 6.7, 4.2, 2.5, and 1.3 kHz, respectively. Also prepared PZT cantilever by hybrid method showed 9.2, 3.6, 3.1, 2.4, and 1.2 kHz.. Furthermore, the electromechanical properties of PZT films by sol-gel procedure were also compared with those observed in PZT films by hybrid method.
FP-16 Acoustic Emission Monitoring during Tensile Tests on CrN and CrN/NbN Coated Specimens C. Pecchio, L. Crippa, A. Lizundia (Istituto Scientifico Breda, Italy); E. Bemporad (University of Rome, Italy) Acoustic Emission (AE) analyses was utilised to investigate failure mechanisms in CrN and CrN/NbN coated specimens during tensile tests. When a very fast release of elastic energy occurs during a loading cycle, it generates waves in the range of ultrasound (usually between 20kHz and 1MHz). This short, transient, acoustic emission event produced can be detected and measured so to study local damage within the material during loading (i.e. plastic deformation, cracking initiation and growth). Tensile tests were performed on a MTS (Alliance RT/10) Testing Machine on three micrometers thick CrN and CrN/NbN coated specimens deposited by reactive cathodic arc evaporation onto X5CrNiMo 17 12. Acoustic measurements were also performed on one set of non-coated substrate specimens in order to discriminate events arisen in the substrate during the plastic deformation process. Signals were collected by four transducers: two 'data' sensors , placed on the specimens surface enclosing the area of interest; two 'guard' sensors to discriminate from sources originating outside. Amplitude and absolute energy vs. strain curves associated with microscopy observations allowed the definition of the 'failure strain' for these systems. Failure mechanisms and cracks propagation paths were characterized by SEM/EDS, both in plan view and cross section; the role of surface and bulk defects was evidenced and different behaviour was found in the case of multilayered structure.
FP-17 High-density MIM Capacitors with HfO₂ Dielectrics T.H. Perng (National Chiao-Tung University, Taiwan, R.O.C.); C.H. Chien (National Nano Device Laboratory, Taiwan, R.O.C.); C.W. Chen, C.Y. Chang (National Chiao-Tung University, Taiwan, R.O.C.) In recent years, metal-insulator-metal (MIM) capacitors using one of the standard back-end metal layers as bottom electrode have emerged as key passive components for silicon radio-frequency (RF) and mixed-signal integrated circuits (ICs) applications¹¹². Compared with double poly linear capacitors, they offer the advantages of reduced series resistance and lower parasitic capacitance³. A high capacitance density is important for a MIM capacitor to increase the circuit density and reduce the cell area and cost. Therefore, adoption of high-k material like Al₂O₃ or HfO₂ is a very efficient way to increase the capacitance density⁴. In this work, MIM capacitors with HfO₂ dielectrics were fabricated and investigated. Experimental results show low leakage current of ~10^-⁹ A/cm² and high capacitance density of ~3.4 fF/µm² at 100 kHz in the MIM capacitors. The temperature coefficient and frequency dispersion effect for these MIM capacitors were very small. Different metal electrodes like tantalum, aluminum, copper, and polysilicon were also investigated and compared. Finally, the mechanism of electrical transport was extracted for the HfO₂ MIM capacitors with different electrodes. ¹S. Decoutere et al., in Proc. IEEE Bipolar/BiCMOS Circuits Technol. Meeting, 2000, p. 106.²M. Armacost et al., in Int. Electron Devices Meeting Tech. Dig., 2000, p. 157. ³S. Jenei et al., in Proc. IEEE Topical Meeting Si Monolithic IC in RF Systems, Sep. 2001, p. 64.⁴S. B. Chen et al., IEEE Electron Device Lett., vol. 23, p. 185, Apr. 2002.
FP-18 Structural Evolution of Pd-Mg Bilayers under Repeated Hydrogen Absorption and Desorption Cycles. R. Checchetto, N. Bazzanella, A. Miotello, R.S. Brusa (University of Trento, Italy); P. Mengucci (University of Ancona, Italy) The presence of a catalyst in form of thin film or nanoparticle at the surface of hydride forming elements is an important key to produce fast hydrogen absorption and desorption kinetics in metals used for hydrogen storage. In order to mantain fast kinetics also after a high number of absorption and desorption cycles it is important to preserve the microstructure of the catalyst and to ensure the interface stability. In this paper we present a study on the structural evolution of Pd thin films deposited on Mg, which is an important candidate material for hydrogen storage. Pd-Mg bilayers, 15 and 300 nm thick respectively, were deposited on (100) oriented Si wafer by e-beam deposition. Samples were sumbitted to repeated hydrogen absorption and desorption cycles in order to study the influence of the metal to hydride phase transition on the microstructure of the Pd catalyst and on the Mg-Pd interface stability. Structural analysis were carried out by X-rays Diffraction (GIXRD) and X-rays reflectivity, the interface composition was studied by Secondary Ion Mass Spectroscopy (SIMS), the defect evolution was studied by Positron Annihilation Spectroscopy (PAS). The influence of the structural evolution and stability of the Pd-Mg interface on the properties of the Pd catalyst properties was analysed by Thermal Desorption Spectrocscopy (TDS).
FP-19 Metal-induced Crystallization of Amorphous Si_1-xGe_x by Rapid Thermal Annealing C.H. Yu, P.H. Yeh, S.L. Cheng (National Tsing Hua University, Taiwan, R.O.C.); L.J. Chen (National Tsing Hua University, Taiwan, ROC) Metal-induced crystallization of a-Si_1-xGe_x (x=0.2 and 0.3) thin films on SiO₂ by rapid thermal annealing has been investigated. The presence of Ni can reduce the crystallization temperature of a-Si_1-xGe_x by about 100°C. At 300-400 °C, Ni films reacted with a-Si_1-xGe_x films to form Ni germanosilicides on the top of a-Si_1-xGe_x films. During the crystallization, the Ni atoms migrated into the a-Si_1-xGe_x thin films and piled up at the interface of the poly-Si_1-xGe_x and SiO₂. At 500-600°C, segregated grains were found in annealed Ni/Si_1-xGe_x samples and caused an obvious change in grain morphology of poly-Si_1-xGe_x films. From TEM/EDS analysis, the segregated grains contain higher Ni contents and lower Ge contents than the other regions of poly-Si_1-xGe_x.
FP-20 Fatigue Behavior of a SAE 4340 Steel Coated with Balinit Futura C.J. Villalobos-Gutierrez (Universidad Central de Venezuela, Caracas, Venezuela); G. Mesmacque (IUT A, France); D. Bhat (University of Arkansas); E.S. Puchi-Cabrera (Universidad Central de Venezuela) The present investigation has been carried out in order to study the effect of a coating of Balinit Futura® of approximately 3 µm in thickness, on the fatigue behavior of a quenched and tempered SAE 4340 steel both in air and in a NaCl solution. The coating was deposited industrially in a PAPVD reactor by arc enhanced magnetron sputtering and it is a multilayer film composed of approximately 24 alternate layers of TiN/TiAlN. The presence of the coating gave rise to an increase in the yield strength of the substrate from approximately 962 to 1002 MPa, which allowed the conduction of fatigue and corrosion-fatigue tests under rotating bending conditions at maximum alternating stresses of the order of 612, 650, 688 and 726 MPa. The stress versus number of cycles to failure were correlated by means of a simple parametric relationship of the form proposed earlier by Basquin, which allowed the subsequent computation of the effect of the coating on the fatigue properties of the substrate, as a function of the maximum alternating stress applied to the samples. It has been determined that the presence of the coating gives rise to a moderate increase in the fatigue and corrosion-fatigue life of the coated component that can achieve up to 35% at stresses of 612 MPa and 10% at stresses of 726 MPa. Some fracture surfaces corresponding to selected fatigue samples of coated specimens were analyzed by means of SEM techniques. The aim of such analysis was the study the fracture mechanism that takes place when the substrate steel is coated with this film and how this mechanism is related to the increase in fatigue properties that were observed during testing. The preliminary observations indicate that fatigue cracks are nucleated in the coating and that they do not propagate to the substrate until the entire coating thickness has been consumed.
FP-21 Failure Mechanisms of Hard Metallic Thin Films on Soft Polymeric Substrates C. Coupeau, J. Colin, M. George, J. Grilhe (Université de Poitiers, France) Thin films and coating are commonly used in new technologies for the fabrication of optical, magnetic and electronic devices or for protective applications. High tensile stresses induced by the deposition process may lead to the formation of cracks and consequently to some alterations of the required properties. A good understanding of the cracking phenomenon is thus a key point in the improvement of the quality of the films. Several models based on fracture theory applied to bi-materials have been also performed since the beginning of the 90's. These models underline the strong influence of the Young modulus ratio between the film and the substrate. Metallization of polymers used to manufacture microelectronic components or biologically compatible materials for medical implants, leads for instance to the formation of bi-layers with very different elastic coefficients where the mechanical behavior of the soft polymer substrate must be taken into account. In this work, the propagation of cracks has been studied by means of an experimental apparatus consisting in a tensile device interfaced with an atomic force microscope. This experimental apparatus allows to follow in situ the evolution of sample surface during deformation. In situ atomic force microscopy observations of the fine crack structures have thus been carried out on hard nickel thin films on soft polyimide substrates under tensile stress. It is shown that the cracking of the metallic film induces notable damaging of the polymeric substrate. Finite element simulations of the stress field at the cracks head have been carried out in the frame of elasticity to understand this unexpected phenomenon, since no visible damaging for similar strain condition is observed on the uncoated polyimide samples.
FP-22 A Study on Synthesis and Characteristic of Crosslinked Polyimide/Poly (Silsesquioxane) - like Nanocomposite Thin Film for Gas Separation M.H. Tsai (National Chin Yi Institute of Technology, Taiwan, R.O.C.) The synthesis of crosslinked polyimide/poly(silsesquioxane)-like (PI/PSSQ-like) nanocomposite hybrid thin films for gas separation application are presented. The PI/PSSQ-like films are successfully prepared from the poly(amic acid) (PAA) [4,4'-Diaminodiphenyl ether (ODA) and the 3,3'-Oxydiphthalic anhydride (ODPA)] with end-capped phenyltrialkoxysilane (PTS) and monoaryltrialkoxysilane via a self-catalyzed sol-gel process. p-Aminophenyltrimethoxysilane (APTS) was employed to provide bonding between the PTS and ODA-ODPA phases and control the polyimide block chain length (X) ranging from 5000 to 20000 g mole-1. The object here is to correlate the properties with the silica component, the PSSQ-like content, the polyimide block chain length, the crosslinking density and free volume. The effect of composition of the PI/PSSQ-like on their morphology, thermal stability, thermal expansion coefficient, optical transparency in visible (UV-VIS), dynamic mechanical properties (DMA), gas permeability and gas permselectivity were investigated.
FP-23 Characterization of Titanium Oxide Thin Films Prepared by Radio Frequency Magnetron Sputtering H.C. Yao, W.T. Wu, M.C. Chiu, F.S. Shieu (National Chung Hsing University, Taiwan, R.O.C.) Titanium oxide thin films were deposited by RF magnetron sputtering on Si and glass substrates. The microstructure, surface morphology, and optical properties of the thin films were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and UV/VIS spectrophotometer. Both XRD and TEM results show that the microstructure and crystallinity of the coatings depend upon the RF power, oxygen partial pressure, and deposition time. At low oxygen partial pressure and short deposition time, the amorphous phase prevailed; and vice versa for the crystalline phases, anatase and rutile. Surface morphology and roughness of the coatings also vary with RF power and deposition time. Although the coating thickness of the thin films increases with deposition time, the optical transmittance of the films remains approximately constant (~85%).
FP-24 LiCo₂O₄ Cathode Material Coated with Nano-crystallized ZnO by Sol-gel Method for Li-ion Batteries T. Fang, J.G. Duh (National Tsing Hua University, Taiwan, R.O.C.) LiMn₂O₄ spinel is one of the most promising cathode materials for Li-ion batteries. However, the poor cycleability has limited its practicability. Surface modification of the cathode material with metal oxides is a potential approach to improve the electrochemical properties. In this study, nano-crystallized ZnO was coated on the surface of LiMn₂O₄ powders via sol-gel method. The correlation between the amount of coated ZnO and the cycling behavior of surface-treated LiMn₂O₄ powders was discussed. Moreover, the differences of the cycled cathodes with as-prepared powders on the phase and morphology were also considered. The phase and surface morphology characterization were achieved by X-ray diffraction (XRD) and scanning electron microscope (SEM). Transmission electron microscope (TEM) was applied to reveal the detailed interfacial morphology and structural changes of the cathode material before and after cycling. In comparing the characteristics of bare and coated LiMn₂O₄ powders, improvement in cyceability of the ZnO-coated cathode was explored.
FP-25 Charactrizing Metallurgical Reaction of SnPb Solder with Ni/Cu Under-bump Metallization by Electron Microscopy L.Y. Hsiao, Y.L. Chueh, L.J. Chou, J.G. Duh (National Tsing Hua University, Taiwan, R.O.C.) Ni/Cu under-bump metallization (UBM) for flip-chip application is widely used in electronics packaging. The intermetallic compound (IMC) formed at the interface between SnPb solder and Ni/Cu UBM during reflowing are mainly (Ni,Cu)₃Sn₄ and (Cu,Ni)₆Sn₅. It is important to derive the interfacial characterization between eutectic SnPb flip-chip bump and Ni/Cu UBM in the reliability of solder joint. High resolution transmission electron microscopy (HRTEM) analysis is employed in this study to reveal the morphology and structure for intermetallic compounds. The elemental distribution near the interfacial region is probed by digital X-ray maping. The diffusion of Cu atoms through electroplated Ni is evidenced by energy-dispersive X-ray spectroscopy (EDS). It is aimed to further investigate the detailed interfacial reaction and related diffusion behavior of Cu, Sn and Ni atoms between solders and Ni/Cu UBM during reflowing.
FP-26 Characterization of Hot Wall Grown 1,8-dihydroxy-9,10-Anthraquinone Films for Device Applications A. Mahajan (D. A. V. College, India); R.K. Bedi, S. Kumar (Guru Nanak Dev University, India) 1,8-Dihydroxy-9,10-anthraquinone films has been grown by hot wall technique onto the glass substrates kept at different temperatures in a vacuum of 1.3C 10^-3 Pa. These films are characterized by NMR, optical absorption (IR, visible, near-UV), X-ray diffraction and scanning electron microscopy. Besides these, the electrical properties of the films are determined in the temperature range 290-370 K. Crystallites as large as 7µm are observed in the case of films deposited at 348K. The X-ray diffraction pattern of these films show crystalline behaviour of films. The films deposited at higher substrate temperature suggest the formation of more ordered and crystalline films. Analysis of optical absorption measurements indicate that interband transition energies of films lie in the range 1.80 -2.40 eV. The current-voltage characteristics of films show ohmic behaviour of conduction within the investigated field and temperature range (10-60 V, 290-360 K). The substrate temperature appears to influence the properties of the films. The electrical conductivity, carrier concentration, drift mobility and optical band gap of the films increase with increases in substrate temperature, whereas activation energy decreases. The FTO/1,8-dihydroxy-9,10-anthraquinone/Al Schottky barrier device has been prepared by depositing 1,8-dihydroxy-9,10-anthraquinone onto FTO coated glass slides by hot wall technique. The device so obtained was studied for its J-V characteristics and the typical parameters such as open circuit voltage, short circuit current, fill factor and power conversion efficiency has been calculated.
FP-27 Mechanical Properties of Functional Gradient Nitride Coating with Nickel Phosphorous Interlayer F.B. Wu, S.K. Tien, G.T. Liu, J.G. Duh (National Tsing Hua University, Taiwan, R.O.C.) The sputtering nitride coatings, including CrN, TiN, and TiAlN were deposited onto Mild Steel (MS) with the electroless plated Ni-P interlayer to form a multi-layer coating assembly. A special mechanical testing technique, i.e. continuous-stiffness- measurement (CSM), was employed to elucidate the integrity of the properties of the multi-layer coatings. The dependency of mechanical properties, such as hardness and Young's modulus, on indentation depth was investigated through the continuous testing technique. A sharp drop in hardness was observed as the indenter penetrated through nitride coating, while there was no significant fluctuation in the modulus of the multi-layer coating assemblies. The influence by various nitride coating in the integrated mechanical properties was explored. In addition, the effect of Ni-P interlayer incorporation on mechanical performance of various coating assemblies was also discussed.
FP-28 Boron-carbide Barrier Layers in Scandium-silicon Multilayers A.F. Jankowski (Lawrence Livermore National Laboratory) Silicon-based multilayer structures are widely used as mirrors to reflect a range of soft x-ray wavelengths up to the extreme ultra violet. Recent investigations show that scandium-silicon multilayer structures can efficiently reflect x rays at a 47 nm wavelength as generated from a laser source. However, the intrinsic metastability of a silicon-based multilayer structure can lead to the formation and growth of silicide compounds that broaden interfaces and consequently cause a change in the layer spacing and loss of reflectivity. To address the problem of a change in layer spacing, Vinogradov et al. have used thin tungsten layers, less than 1 nm thick, deposited at each interface to serve as a diffusion barrier. Unfortunately, the use of tungsten adversely affects the reflectivity of the multilayer mirror due to adsorption. For example, the reflectivity measured at normal incidence of a 20 nm multilayer decreased by half its peak value with the addition of tungsten barrier layers. An alternate material choice is now presented to serve as a diffusion barrier based on our prior substitutive use of boron carbide to stabilize carbon-based multilayer structures. Scandium-boron carbide-silicon multilayers that are prepared by planar magnetron sputter deposition do not show a significant loss of reflectivity in the extreme ultra violet regime. For example, the reflectivity of a 19 nm scandium-silicon multilayer is affected by only a few percent of its peak value when boron carbide layers are added to each interface. The stability of layer spacing for multilayer structures with the boron-carbide barrier layers is shown using grazing incidence diffraction for samples subjected to vacuum anneal treatments. This work was performed under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.
FP-29 A Model for the Temperature Dependence of Electrical Conductivity in Lead Phthalocyanine Thin Films Showing Space-Charge-Limited Conductivity T.S. Shafai (Staffordshire University, United Kingdom); R.D. Gould (Keele University, United Kingdom) Many of the phthalocyanines exhibit p-type conductivity, and electrical conductivity through thin films of these materials having ohmic contacts show space-charge-limited conductivity (SCLC) dominated by trap levels located within the bandgap. In the present work evaporated thin films of lead phthalocyanine with ohmic Au electrodes were prepared, which showed two distinct regions in the dependence of current density J on applied voltage V. At low voltages sample conductivity was ohmic, changing at higher voltages to a V² dependence, which is indicative of SCLC dominated by trap levels located at a single discrete energy level. The results of temperature measurements indicate three distinct regions, in each of which the hole concentration is controlled by a different activation energy. A simple model is proposed in which a single trap level is located at the same energy spacing E_t from the valence band edge as a single acceptor level. This predicts three different temperature ranges, two of which correspond to those covered by the experimental results. The experimantal results indicate a trap level located at an energy E_t = 0.36 eV above the valence band edge and a thermal band gap E_g = 1.51 eV. Using the proposed model together with data from the experimental J-V characteristics, an acceptor concentration of 4.85 x 10¹⁹ m^-3 and a trap concentration of 5.18 x 10²⁵ m^-3 are indicated. Measurements of mobility based on this model yield a value of 2.6 x 10^-4 m² V^-1 s^-1, which is in close agreement with previous work.
FP-30 Measurement of Mechanical Properties of Thin Films Utilizing Ultrasonic Scanning Tunneling Microscope Technique O.G. Lysenko, N.V. Novikov, S.L. Shapovalov (Institute for Superhard Materials, Ukraine) We present acoustic-based technique to investigate mechanical properties of thin films with nanometer spatial resolution. The technique feature is using two tunneling tips as local acoustic probes to detect phase and amplitude of the acoustic waves at a surface of solids. This approach makes it possible to measure very small changes in acoustic transit time. For example, this change arises from the variation of the sound velocity with temperature, and also has a contribution from thermal stress in the film. By making accurate measurements of the transit time, it is possibly to identify the onset of plastic flow in the film. Also various applications of the technique to measure elastic modulus of diamond and diamond-like thin films are described. The technique is non-contact and does not require the destruction of the sample. Measurements can be made within small areas of a thin film.
FP-31 Surface Analysis of the Wear of TiN/Ti Multilayers Deposited by Sputtering with Variable Magnetic Field M.F.M. Flores (CUCEI, Universidad de Guadalajara., Mexico); L.H.A. Huerta, S. Muhl (UNAM, Mexico) TiN/Ti multilayers have been deposited by magnetron sputtering to improve the corrosion and wear resistance of metallic substrates. In this work we report the results of preparing multiple TiN/Ti layers on H13 steel substrates by reactive magnetron sputtering, with an additional magnetic field, applied by a coil concentric to the magnetron. We report the results of studies of the influence of magnetic field on the wear abrasion resistance of TiN/Ti multilayers; with layers of Ti deposited during 4 minutes and TiN deposited during 10 min, the number of periods was 6. The wear was studied using a commercial ball cratering system. It was found that magnetic field enhanced the ion bombardment and this in turn modified the microstructure which improve the wear resistance of multilayers. The periodical multilayer were compared with a monolithic and some relatively thick (5-10 microns) multilayers. The XRD analysis was used to study the influence of the magnetic field on the texture and interplanar distances of multilayers. The composition of the films was determined by RBS and Auger deep profile. In order to found the compound created during the wear, the surface of crater wore was analysed by XPS and AES techniques.
FP-32 Energy Distribution of Ar⁺ Ions and Cu⁺ Ions Incident on a Substrate using rf and dc Magnetron Sputtering Systems T. Miyamoto, M. Ohnishi, K. Kawabata (Hiroshima Institute of Technology, Japan); H. Kajioka (Industrial Research Institute Hiroshima Prefecture West, Japan) The energy distribution of ⁴⁰Ar⁺ ions and ⁶³Cu⁺ ions incident on a substrate using rf and dc magnetron sputtering systems with a copper target (200 mmφ) was examined by an energy-resolved mass spectrometer PPM 422 (Balzers) whose orifice was set 260 mm in front of the sputtering target. Argon gas pressure was kept at 1.0 Pa. Increasing the rf power from 0.3 to 2.0 kW, the width of the energy distribution of Ar⁺ ions and Cu⁺ ions with saddle-shape characteristic increases from 4 - 26 eV to 0 - 47 eV and from 24 - 25 eV to 0 - 80 eV, respectively, and the mean ion energy of Ar⁺ ions and Cu⁺ ions increases from 24 to 33 eV and from 25 to 35 eV, respectively. The number of ions increases from 1.8x10⁶ to 1.1x10⁷ cps and from 8.0x10¹ to 1.0x10⁷ cps, respectively, and the ratio of the number of Cu⁺ ions to Ar⁺ ions increases from 4.4x10^-5 to 9.0x10^-1. As for dc sputtering, increasing the dc power from 2.0 to 5.0 kW, the width of the energy distribution of Ar⁺ ions and Cu⁺ ions with no saddle-shape characteristic is no change in the range of 0.5 - 3.0 eV, and the mean ion energy of Ar⁺ ions and Cu⁺ ions is no change at 2.0 eV. The number of Ar⁺ ions which reaches maximum value of 1.0x10² cps at dc power of 3.0 kW is much less than the number of Cu⁺ ions which logarithmically increases. The ratio of the number of Cu⁺ ions to Ar⁺ ions increases from 2.3x10¹ to 3.2x10³ in the range of dc power of 2.0 - 4.0 kW. In comparison with rf sputtering, the width of energy distribution of Ar⁺ ions and Cu⁺ ions is very narrow, the energy of both Ar⁺ and Cu⁺ ions is significantly low, and the number of Ar⁺ ions and Cu⁺ ions is small, although the number ratio of Cu⁺ ions to Ar⁺ ions is significantly large.
FP-33 Adhesion Strength and Interface Analysis of Polyimide/Titania Hybrid Films and Copper System P.C. Chiang, W.T. Whang (National Chiao-Tung University, Taiwan, R.O.C.) Polyimides have been widely utilized for the micro-electronic and composite applications. This is attributed to the fact that polyimides offer high thermal stability, good mechanical property, low moisture absorption, low dielectric constant and good chemical resistance. The hybrid films of polyimide incorporated with titania were applied for Polyimide/copper system. Besides, the plasma treatment is used to enhance the adhesion strength between metal and polymer by modifying the morphological and chemical properties of the interface. Peel test was performed to evaluate the adhesion strength of Polyimide/copper system. A tendency that adhesion strength of the Polyimide/copper system can be greatly improved by adding a small amount of titania (1~3% by weight) was observed. The effect of titania content on corrosion protection and adhesion promotion was investigated by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and scanning electron microscopy (SEM).
FP-34 Study on Etching Profile of Nano-porous Silica C.W. Chen (National Chiao Tung University, Taiwan, R.O.C.); T.C. Chang (National Sun Yat-Sen University, Taiwan, R.O.C); P.T. Liu (National Nano Device Laboratory, Taiwan, R.O.C); Y.J. Mei (Ching-Yun Institute of Technology, Taiwan, R.O.C.); T.M. Tsai, T.Y. Tseng (National Chiao Tung University, Taiwan, R.O.C.) We have investigated the impact of H₂-plasma treatment on nano-porous silica (k=2.0). The etching rate of trenches of nano-porous silica film was about 650 nm/min using fluorocarnbon plasma. It is 1.6 times the etching rate of CVD oxide for the same etching condition. This result is expected because the porous silica has a lot of air pores. We found that the profile of the intrinsic samples had mask undercutting. By the contrary, there were no mask-undercutting effects on the H₂-plasma treated samples. Based on FTIR spectra analysis, the Si-H bonding was appeared after H₂-plasma treatment. The mount of H atoms in the porous silica could react with fluorocarnbon radicals and ions. As a result, the spontaneous reactive etching at sidewall was suppressed. We also observed the pattern profile of porous silica was distorted after O₂-plasma ashing. This is due to the oxidation of hydrophobic groups and formation of Si-OH bonds in the bulk.
FP-35 Study on The Effect of Electron Beam Curing on Low-K Organic Silica Glass (OSG) Material T.C. Chang (National Sun Yat-Sen University, Taiwan, R.O.C); T.M. Tsai (National Chiao-Tung University, Taiwan, R.O.C.); P.T. Liu (National Nano Device Laboratory, Taiwan, R.O.C); C.W. Chen, S.T. Yan (National Chiao-Tung University, Taiwan, R.O.C.); Y.T. Chen (National Sun Yat-Sen University, Taiwan, R.O.C.); T.Y. Tseng (National Chiao-Tung University, Taiwan, R.O.C.) This paper presents the effect of electron beam (e-beam) curing on a low dielectric constant (low-k) material, organic silica glass (OSG). In conventional multilevel manufacture process, photoresist (PR) stripping with O₂ plasma and wet chemical stripper is an inevitable step. However, dielectric degradation often occurs when low-k dielectrics undergo the PR removing process. This will limit the application of incorporating low-k materials into semiconductor fabrication. Therefore, e-beam curing process was used to overcome this issue. In this study, the possible doses of e-beam exposed OSG are identified by Fourier transform infrared spectroscopy, n&k 1200 analyzer and electrical analysis. In addition, there are five chemical solution evaluated to serve as the developer of e-beam cured OSG films for IC manufacture process. These experimental results express that the dielectric regions illumination by e-beam will be cross-linked gradually with the increase of e-beam dosage. The aqueous solution, whose composition is 1.25 wt % tetra-methyl ammonium hydroxide (TMAH): methanol =1:8, can cause high selectivity between e-beam cured and un-cured regions. While the dosage of e-beam exceeds 6 µC / cm², the thickness of post-exposed OSG films can be remained after developed process, which is similar to commercial e-beam resists. Finally, the electrical properties of e-beam exposed OSG films can be recovered to similar to the standard furnace curing one utilizing an extra thermal annealing process.
FP-36 Cu Penetration Induce Breakdown Mechanism for A-SiCN P.T. Liu (National Nano Device Laboratory, Taiwan, R.O.C.); C.W. Chen (National Chiao Tung University, Taiwan, R.O.C.); T.C. Chang (National Sun Yat-Sen University, Taiwan, R.O.C); J.H. Yang, S.H. Wu (National Sun Yat-Sen University, Taiwan, R.O.C.); F.M. Yang, T.Y. Tseng (National Chiao Tung University, Taiwan, R.O.C.) Amorphous SiC are promising candidates for Cu barriers due to low permittivity (4~5) relative to SiN (k=8) and good barrier ability. We have investigated the leakage mechanism of amorphous SiCN films after bias-temperature-measurement (BTS) with Cu electrode. The leakage current became very large due to the Cu ions penetration after strict BTS condition. Then the electrical measurement of the breakdown sample was performed in cryogenics system. With the decreasing temperature, the leakage current was still large in negative bias but getting smaller in positive bias. The distribution profile of Cu ions is depicted by SIMS spectrum. It is apparent that Cu ions penetrated into the SiCN film and even reached to the interface between SiCN/Si due to BTS measurement. The Cu ions existing in silicon carbide would be taken as trap states and could enhance the carriers to transport. We purpose a model to interpret the leakage mechanism of breakdown SiCN samples due to Cu ions.
FP-37 Structural Characteristics and Interfacial Reactions of Low-dielectric Constant Porous Polysilazane for Cu Metallization J.H. Wang (National Tsing Hua University); P.T. Liu (National Nano Device Laboratory, Taiwan, R.O.C); T.S. Chang (National Tsing Hua University, Taiwan, R.O.C.); T.C. Chang (National Sun Yat-Sen University, Taiwan, R.O.C); L.J. Chen (National Tsing Hua University, Taiwan, R.O.C.) The structural and electrical properties of porous ploysilazane (PPSZ) have been characterized. The dielectric constant of PPSZ film was as low as 2.2 owing to the high porosity and uniformity of the film. The copper silicide was found to form between Cu and the PPSZ film after annealing at 550°C for 30 min due to the SiO desorption from PPSZ. The oxidation behaviors on broken PPSZ films catalyzed by copper silicide were found. The copper silicide reacts with oxygen in PPSZ to form Cu and SiO₂ at room temperature. The leakage current of the broken PPSZ film after annealing at 550°C for 30 min was found to decrease with exposure in air for a few days at room temperature.
FP-38 AFM/STM of Ion Etched Cross Sections. a Method for the Analysing the Morphology of Dense Hard Coatings. A. Santana (Federal Institute of Technology, Switzerland); B. Burdet, A. Toppo, M. Jobin, E. Bergmann (Geneva School of Engineering, Switzerland) Mirror poished cross sections of hard coatings on carbide substrates were ion etched with different conditions to create a relief. This relief was then analysed with STM and various AFM modes. The mehod gives very usefull information on the morphology of the coatings. The results were compared with TEM observations on the same cross sections and surface AFM analysis. While the observations are also a simple alternative to TEM, they give essentially complementary information on density of grain (column) boundaries and the interlamellar growth in multilayer stacks.
FP-39 X-ray Characterization of Oriented β-tantalum Films S. Kohli, P.R. McCurdy, C.D. Rithner, P.K. Dorhout, A.M. Dummer, C.S. Menoni, F. Brizuela (Colorado State University) Recently, copper metallization has been extensively explored as an interconnect for ULSI applications. However, an underlying layer is needed for adhesion of Cu to dielectrics as well as a diffusion barrier to prevent the drift of the copper ions through the dielectric layer.¹ The texture and grain structure of Cu films has been shown to effect the electromigration lifetime of Cu interconnects.² The electromigration lifetime of (111) oriented Cu was reported to be about four times longer than that of oriented Cu(200).² It has also been shown that the growth of Cu(111) is preferred on β-Ta films oriented along (002) crystallographic plane.³ In spite of the various studies devoted to investigating the structural and growth properties of β-Ta, the growth mechanism of this material is not clear. There seems to be insufficient information related to the properties of the interface between oriented β-Ta and the underlying substrate/layer. In the present study, 10-70 nm tantalum films were deposited on Si(100) substrates with a 500 nm SiO₂ interlayer by Ion-Beam assisted sputtering. X-ray diffraction measurements showed the presence of highly textured β-tantalum films oriented along (00l) plane. X-ray Reflectivity measurements indicate the presence of a thin interface layer between β-tantalum films and 500 nm SiO₂ film. X-ray Photoelectron Spectroscopy depth profiling indicate that the interface layer is essentially comprised of a mixture of Ta₂O_5-x and SiO₂. Recent results from these investigative studies will be reported. ¹. S. P. Murarka and S. W. Hymes, Crit Rev Solid State 20 (1995) 87. suepr 2. C. Ryu, K. W. Kwon, A. L. S. Loke, H. Lee, T. Nogami, V. M. Dubin, R. A. Kavari, G. W. Ray, and S. S. Wong, Ieee T Electron Dev 46 (1999) 1113. ³. K. V. Kwon, C. Ryu, R. Sinclair, and S. S. Wong, Appl Phys Lett 71 (1997) 3069.
FP-40 Indication of Spinodal Decomposition in GalnAsN Epitaxial Layers and Thin Films A. Trampert, J.M. Chauveau (Paul-Drude Institute for Solid State Electronics, Germany); E. Tournié (CEM2, Universite de Montpellier II-CNRS, France); A. Guzmàn (Universidad Politecnica de Madrid, Spain); K.H. Ploog (Paul-Drude Institute for Solid State Electronics, Germany) Quaternary alloys of (Ga,In)(As,N) are belonging to the group of III-V semiconductor compounds which crystallize in the zinc-blende lattice, i.e. consisting of two fcc lattices shifted by (1/4,1/4,1/4) against each other. Because of the large differences in electronegativity and atomic size between the constituents of both group-III and group-V sub-lattices, theoretical calculations based on thermodynamic properties predicts spinodal decomposition of the quaternary alloy by over a wide range of composition. On the other hand, thin film processes are generally described as non-equilibrium processes, why the origin of these composition fluctuations is not only discussed regarding the phase separation tendency but also with respect to epitaxial strain and kinetically limited ordering. We present a systematic study of the microstructure of thin (Ga,In)(As,N) epitaxial layers and thicker films grown on GaAs substrates with various alloy contents. Our TEM investigations of as-grown and annealed samples reveal the following results: (i) composition fluctuations and morphological instabilities are not mainly driven by epitaxial strain. (ii) There are two types of composition modulation with different periodicity, and (iii) material hardening is found as assumed by the presence of spinodal decomposition. These results are finally discussed in connection with the growth conditions and annealing procedures.
FP-41 Determining Chemical Composition through X-Ray Photoelectron Spectroscopy K.A. Adamson (Bringham Young University) This study involves the chemical composition of thin films (100-200 angstroms) of uranium oxide, created through DC magnetron sputtering. The oxidation of the uranium surface is investigated through x-ray photoelectron spectroscopy (XPS). The uranium sample is placed under high vacuum and bombarded with x-rays of known energies. Uranium oxide molecules are ionized and the energy of the ejected electrons is determined by an electron detector. By this method, the bonding energy of the electron is determined. The data shows that the surface oxidizes gradually over a period of several weeks. By comparison with the work of Teterin ('A Study of Synthetic and Natural Uranium Oxides by X-Ray Photoelectron Spectroscopy', J. Phys. Chem. Minerals. 1981), our thinner samples are a mixture of UO₂ and UO₃, with UO₃ becoming more prominent as the sample has more time to oxidize. The composition below the surface is studied by using an ionized ray of argon ions to sputter off layers of the film, periodically examining with XPS. It has been found that nitrogen is present in the film, how it is bonded to the uranium is unknown. The amount of oxygen decreases with depth.
FP-42 Ferroelectric Properties of Bi_4-XEu_XTi₃O₁₂ Thin Films Prepared by Low-temperature Sol-gel Method using LNO Electrode C.I. Kim (Chung-Ang University, South Korea); C.I Lee (Ansan College of Technology, South Korea); K.T. Kim (Chung-Ang University, South Korea) Bi_4-XEu_XTi_3Osub 12 (BET) thin films were prepared by sol-gel method onto the LaNiO₃ (LNO) bottom electrode. We have systematically investigated the variation of solvents depending on the process condition. The structure and morphology of the films were analyzed by x-ray diffraction (XRD), and atomic force microscope (AFM). AFM showed uniform surface of the films. The BET thin films exhibited (117) orientation and were successfully deposited on LNO bottom electrode by using sol-gel method even at a low temperature ranging from 450 to 650°C. The BET thin films annealed at 600°C on LNO bottom electrode exhibited no significant degradation of switching charge at least up to 5 X 10⁹ switching cycles at a frequency of 100 kHz and 5 V. It was shown experimentally that there was no data loss after 2 X 10⁴'s of memory retention at room temperature.
FP-43 Properties of TiO₂ Thin Film Deposited by Cathodic Vacuum Arc Technique W.-T. Hsiao, M.-S. Leu, N. Yang, L.-G. Chao (Industrial Technology Research Institute, Taiwan, R.O.C.) The present paper describes the properties of TiO₂ thin film that prepared by CVA (Cathodic Vacuum Arc) process. In this study, Titanium target was prepared to coat TiO₂ thin film on the glass. The transparent measurement shows that increase percentage of Oxygen will increase transparent of thin film. As the percentage of Oxygen is about 55%, transparency of thin film is measured of about 48%. While the percentage of Oxygen increase to 100%, transparency of thin film can be increased to about 89%. Besides, as the vacuum pressure is increased from 0.4Pa to 1.3Pa, the transparency of film is also increased from 37% to 79%. The result of electric resistance measurement also shows that increase percentage of Oxygen will increase electric resistance of the film, such as the percentage of Oxygen is increased to about 90%, the electrics resistance of thin film will increase to attain about 5*108Î©. However, as the coating bias voltage increased, X-ray diffraction data shows that coating structure will get more Rutile structure.
FP-44 Raman Analysis of Si-C-N Thin Films Prepared by Reactive Magnetron Sputtering J. Leme, E. Liang, C. Moura, L. Cunha (Universidade do Minho, Portugal) Films of Si-C-N were deposited, on steel and glass substrates, by reactive magnetron sputtering and co-sputtering. In the films prepared by magnetron sputtering of silicon and carbon targets the argon flow was kept at 100 sccm and the nitrogen flow kept at 10 sccm. The negative substrate bias varied from 0 to -125 V. The co-sputtered films were grown in a rotation mode using a fixed silicon fraction on the carbon target erosion area. The nitrogen flow varied from 0 up to 20 sccm and the substrates bias voltage varied from -50 V up to +50 V and. The as-deposited films were analyzed by Raman spectroscopy (RS) using two different excitation lines (633 nm and 488 nm. The main features observed in the RS are the two broad bands at ~1360 cm-1 (D-band) and ~1580 cm-1 (G-band), characteristic of amorphous carbon materials. The relative intensity and the position of the bands are shown to be correlated with the deposition conditions. The ratio between their intensities (I_D/I_G) is found to increase with the variation of the substrate bias voltage from negative to positive polarization and also increases with the increase of the nitrogen flow. The position of the D-band is almost constant and the position of the G-band decreases with the variation of the bias voltage from -50 V to +50V. Raman analysis indicates the changes in carbon and nitrogen configuration in the films (mixed sp³-sp² hybridization).
FP-45 Structural Evolution in ZrN_xO_y Thin Films as a Function of Temperature: a Comprehensive Study in Vacuum L. Cunha, F. Vaz, C. Moura, L. Rebouta (Minho University, Portugal); E. Alves (ITN, Portgual); A. Cavaleiro (Coimbra University, Portgual); Ph. Goudeau, J.P. Rivière (Université de Poitiers, France) Microstructural stability is one of the most important aspects to be considered in materials processing, particularly in the case of coatings to be used in aggressive environments, such as high temperatures and high mechanical loading. In these cases, changes at the microstructural level are frequent involving modification of crystalline size and structural evolution. Moreover, processes of stress relaxation by creep, microfissuration or localised losses of adhesion at the interface with the substrate are frequent at high temperatures, which can determine the mechanical behaviour of the coatings. All these changes may, in the most dramatically perspective, lead to the full loss of the coating making impracticable the use of the coated part. ZrN_xO_y thin films were deposited at a constant temperature of 300°C by rf reactive magnetron sputtering. A set of films was prepared with the variation of substrate bias voltage whereas in the other set the flow rate of reactive gases was varied. The presence of the oxygen allows tailoring the film properties from those of covalent zirconium nitride to those of the correspondent ionic oxide. The thermal stability of the coatings was tested in vacuum for an annealing time of 1 hour, in the temperature range from 500° to 900°C. Rutherford Backscattering Spectrometry (RBS) was used for the analysis of the overall chemical composition of the as-deposited coating as well as the depth profile contents through the thickness of annealed samples. The structure of both as-deposited and annealed samples was assessed by X ray diffraction (XRD). All the structural and chemical composition changes induced by both variations of the deposition parameters (bias voltage and the O/N ratio) and the annealing conditions are analysed and discussed in detail.
FP-46 Hardening Mechanisms in Superhard (Ti,Si,Al)N Nanocomposite Coatings S. Carvalho, L. Rebouta, F. Vaz (Universidade do Minho, Portugal); A. Cavaleiro (Coimbra University, Portgual); E. Alves (ITN, Portgual) This work reports on the study of the hardening mechanisms found in superhard (Ti,Si,Al)N coatings, prepared by reactive magnetron sputtering. The chemical composition, thickness, film structure and the mechanical properties were investigated by Rutherford Backscattering (RBS), Electron Probe Microanalysis (EPMA), ball-cratering, X-Ray Diffraction (XRD) and ultramicroindentation, respectively. A significant increase in hardness with increasing Si addition was observed till a maximum close to 60 GPa in the Ti_0.50Si_0.13Al_0.37N sample. This behaviour was interpreted owing to decreasing lattice parameter and increasing grain size. The incorporation of smaller silicon atoms into the fcc TiAlN lattice leads to a decrease on the lattice parameter and to a local tensile stress (lattice distortion), which contributes to the observed hardening. However for films prepared with different bias voltage an opposite behaviour is found since there is a good correlation between the increase of the hardness and both the increase of lattice parameter and decrease of grain size. For these samples the development of a nanocomposite of the type nc-TiAlN/a-Si₃N₄ seems to the main feature to interpret the hardness increase.
FP-47 Formation of Aluminide Phases on Ti Substrate during Annealing and Ion Irradiation S. Romankov (Institute of Physics & Technology, Kazakhstan) The aluminum layer on the titanium substrate has been formed by thermal deposition. The structural formation of aluminide phases on the Ti substrate has been studied. The sequence of structural transformations at the Ti/Al interface is limited by the reaction temperature and time. The sequence of aluminide phase formation is occurred in compliance with Ti-Al equilibrium phase diagram. At the initial stages at the Ti/Al interface the Al₃Ti alloy starts forming as a result of interdiffusion, and gradually the whole aluminum film is spent on the formation of this layer. The Al₃Ti layer decomposes with the increase of temperature (>600C). At 800C the two-phase (Ti₃Al + TiAl) layer is formed on the titanium surface. The TiAl compound is unstable and later on with the increase of the exposure time at 800C gradually transforms into the Ti₃Al. The chain of these successive transformations leads to the formation of the continuous homogeneous layer consisting of the Ti3Al compound on the titanium surface. At temperatures exceeding the allotropic transformation temperature (>900C) the Ti₃Al compound starts decomposing. All structural changes taking place at the Ti/Al interface are accompanied by considerable changes in microhardness. Ion irradiation influences on kinetics of phase transformation. Prior ion irradiation of Ti substrate accelerated formation of aluminide phases.
FP-49 Structural, Friction and Wear Behaviour of Reactive Magnetron Sputtered TiN Thin Films C.J. Tavares, F. Vaz (Universidade do Minho, Portugal); A. Komraus (University of Konarskiego, Poland); D. Munteanu, C. Davidescu, F. Borza, S. Bobancu (Transilvania University, Romania); E. Alves (Instituto Tecnologico Nuclear, Portgual); L. Rebouta (Universidade do Minho, Portugal) The present paper reports the influence of preparation conditions, such as dc power applied at the Ti target and bias voltage, on the physical/structural and mechanical behavior of TiN thin films, deposited by dc magnetron sputtering in the low-pressure range. Regarding structural characterization, a preferred orientation with the {111} planes parallel to surface was observed. By increasing the dc power on the Ti target or increasing the substrate bias, the texture effect in the films is favored. Mechanical properties such as static friction coefficient, wear, hardness, adhesion and residual stresses are characterized and discussed as a function of structural properties and the deposition parameters. A minimum value for the static friction coefficient was obtained for the unbiased sample, which presented a very good tendency for sliding. A low level of compressive stresses was also obtained in this sample. With increasing ion bombardment the friction properties become worse. The wear behavior of the coatings has been estimated using a special pin-on-disk tribosystem. The wear tests consisted in five cycles (5 minutes/cycle) of holding load. The preliminary results seem to show a good correlation between the wear tests and the friction behavior. Thermal anneals in vacuum at 800°C were performed on these samples, revealing that the coatings maintained their favored crystalline texture with an increase in both grain size and lattice parameter due to the relaxation of the high compressive stresses. A statistical analysis was performed on the surface defect density of the TiN thin films, which concluded that as the negative bias voltage increased the defect density and average defect area increased. This is in agreement with the behavior of the static friction coefficient since an increase in defect density leads to roughening of the film surface and to a decrease in wear resistance.
FP-50 Raman Study of Structural Transformation in ZrN_XO_Y Thin Films: Effect of Deposition Conditions and Thermal Treatment C. Moura, F. Vaz, L. Cunha, L. Rebouta (Minho University, Portugal); E. Alves (ITN, Portgual); A. Cavaleiro (Coimbra University, Portgual); Ph. Goudeau (University of Poitiers, France); J.P. Rivière (University of Poitiers - France) Structural properties of single layered zirconium oxynitride, ZrN_xO_y, thin films were investigated by Raman spectroscopy (RS) and X-ray diffraction (XRD). These structural characterisation tools were used either for the analysis of the as-deposited samples and to identify the structural changes arising from the thermal treatment of the thin films. Monolithic ZrN_xO_y,thin films were deposited at 300°C by rf reactive magnetron sputtering. The depositions were carried out from a pure Zr target. Two sets of films were prepared: in the first set the substrate bias voltage was varied whereas in the other set the attention was pointed for the variation of the flow rate of reactive gases. The presence of the oxygen allows tailoring the film properties between those of covalent zirconium nitride and those of the correspondent ionic oxide. The thermal treatment of the coatings was performed in vacuum, in the temperature range from 500°C to 900°C. The lines shapes, the frequency and widths of the Raman bands are analysed as a function of the annealing temperature. On the basis of Raman results and X-ray diffraction patterns, it is shown that the structural transformations are dependent of the deposition parameters (bias voltage and O/N ratio) and the annealing conditions. These structural changes are analysed and discussed in detail.

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