ICMCTF2000 Session F5-2: Characterization of Thin Film Growth Processes and Evolving Film Properties

Thursday, April 13, 2000 1:30 PM in Room San Diego

Thursday Afternoon

Start	Invited?	Item
1:30 PM	Invited	F5-2-1 Fluorocarbon Film Growth From Polyatomic Ions: Implications for Plasma Polymerization L. Hanley (University of Illinois at Chicago) Mass selected polyatomic ions beams can both create new materials similar to plasma polymers and elucidate polyatomic-surface collision mechanisms that are fundamental to plasma polymerization and etching. Polyatomic ions can impart both specific chemical functionality and nanoscale structure to a wide variety of substrates. The fluorocarbon ions are studied here due to their technological relevance, the large number of previous studies on related systems, and their ability to illuminate several fundamental points in polyatomic ion-surface modification and plasma polymerization. Polystyrene has been chosen because it is a typical polymer surface whose lack of heteroatoms facilitates its surface chemical analysis. Previous experiments with 10 - 100 eV SF₅⁺ and C₃F₅⁺ indicated different chemistry with polystyrene surfaces. This work is continued here by examination of 25 - 50 eV CF₃⁺ vs. C₃F₅⁺ ion reactions with polystyrene surfaces using monochromatic x-ray photoelectron spectroscopy and molecular dynamics simulations. These two fluorocarbon ions display significantly different surface chemistry at these low kinetic energies that cannot be explained simply by eV/atom arguments. These results are related to mechanisms of surface modification by fluorocarbon plasmas.
2:10 PM		F5-2-3 Etching SiO₂ Aerogel of Film using CF₄/H₂ Plasma in Reactive Ion Etching H.H. Park, J.J. Kim (Yonsei University, Korea) SiO₂ aerogel film fabricated by sol-gel process has low dielectric constant due to three-dimensional network structure. In order to apply the film to an integrated circuit, most of all, O₂ plasma treatment is required because it could control the internal surface chemical species of SiO₂ aerogel film. CF₄ plasma etching is easily adapted as a dry etching using RIE. Plasma etching of SiO₂ using mixtures of CF₄ and H₂ gases is commonly used to obtain the high selective of SiO2/Si etching in RIE. H₂ addition should increase the HF concentration and decrease the F concentration in the plasma. Therefore, the etch selectivity increases, while the etch rate decreases. In this work, we performed the etching of SiO₂ aerogel film using CF₄ and H₂ gases by varying their mixing ratio. The effect of RF power and pressure on the etching of the films was also investigated.
2:30 PM		F5-2-4 Nucleation and Growth of Metal Oxide Deposited by PVD on Surfaces of Poly(ethylene terephthalate) and Oriented Polypropylene C.S. Deng (Department of Materials, United Kingdom); H.E. Assender, F. Dinneli, O.V. Kolosov, G.A.D. Briggs (Oxford University, United Kingdom); T. Miyamoto, Y. Tsukahara (Toppan Printing Company, Japan) The nucleation and initial stages of growth of gas barrier metal oxide layer deposited on two different polymer surfaces (poly(ethylene terephthalate), PET and oriented polypropylene, OPP) by electron beam evaporation were investigated using atomic force microscopy. Permeation of oxygen and water vapour through the thin oxide/polymer composites were also measured. It was found that the initial stages of the growth first form separated islands on each polymer surface. Further growth of oxide depends strongly on the surface morphology and chemical nature of the polymer surface. Growth on PET follows a layer-by-layer mechanism that maintained the native surface roughness of the polymer substrate. The growth on OPP, however, followed an island mode, which led to an increase in surface roughness. This may be due to a lack of chemical bonding between the polymer and arriving metal-oxygen particles. It was also found that the oxide layer on PET packed more densely than on OPP, leading to a greater gas barrier for the former than the latter.
2:50 PM		F5-2-5 Microstructural and Chemical Characterization of Compositionally Modified Metal Oxide Gas Barrier Films. A.G. Erlat, B.M. Henry (Department of Materials, University of Oxford, United Kingdom); J.J. Ingram, D.B. Mountain, H. Nörenberg (University of Oxford, United Kingdom); R.P. Howson (Loughborough University, United Kingdom); C.R.M. Grovenor (University of Oxford, United Kingdom); G.A.D. Briggs (Oxford University, United Kingdom); Y. Tsukahara (Toppan Printing Company, Japan) In the last decade, metal oxide layers deposited on polymer substrates have been utilised as gas barrier films in food packaging as an alternative to the traditional aluminium foil. The resistance of these composite films to gas transmission is controlled predominantly by nano-scale defects created during the fabrication of the oxide layer. The size and density of these defects are believed to be strongly dependent on the intrinsic properties of the metal oxide layer. Modifying the chemical composition of these coatings by doping will enhance the gas barrier properties of these films. Films fabricated by sputtering with systematically varying composition have been investigated using a range of analytical techniques including x-ray photoelectron spectroscopy, atomic force microscopy, transmission electron microscopy and gas permeation measurements to characterise the barrier properties of the film. The structural observations have been correlated with the measurements of the oxygen and water permeation of the composite.
3:30 PM		F5-2-7 Micro-disperse Particles as Probes for Plasma Surface Interaction H. Kersten (University of Greifswald, Germany); G.M.W. Kroesen (Technical University of Eindhoven, The Netherlands); H. Deutsch (University of Greifswald, Germany) The interaction between plasma and injected micro-disperse powder particles might be used as a tool for the study of plasma wall processes in technological applications of low pressure plasmas. Powder particles have been used, for instance, as micro-probes for the determination of the electric field in front of electrodes and substrates as well as for the observation of the energy fluxes between plasma and surfaces. If dust particles are injected into a plasma, they are negatively charged and confined in the discharge. The trapping is due to the balance of the forces acting on the particles. By observing the position and movement of the particle in dependence on the discharge parameter one can obtain information on the electric field in front of surfaces where other plasma diagnostic methods fail. In addition, the particles have also been used as microscopic thermal probes. The equilibrium temperature of the particles, which is a result of the several energy fluxes from the plasma, has been determined by temperature-dependent fluorescence of laser dye mixed with the micro-particles. By considering the involved energy gain and loss mechanisms, respectively, the thermal balance of the particles has been estimated and the resulting equilibrium temperature has been compared with the particle temperature measurements. In case of an argon plasma the heating of the particles by charge carrier recombination could be identified as dominant energetic contribution, while the losses are due to radiation and conduction.
3:50 PM		F5-2-8 The Bilayer Structure of Al-0.5 wt.%Cu Film Induced by Ar Sputtering Pretreatment L.P. Wang, A. Chuang, F.S. Huang, J. Hwang (Tsing Hua University, R.O.C.) A bilayer structure of Al-0.5wt.%Cu film is found induced by Ar sputtering pretreatment, carried out on SiO₂ surface prior to Ti deposition in Al-Cu/TiN/Ti/SiO₂/Si multilayer structure. The microstructure of Al-Cu film was characterized by transmission electron microscopy in cross-sectional view and compared for multilayers with and without Ar sputtering pretreatment. The Al-Cu film of 600 nm thick possesses Al columnar grains with highly Al(111) preferred orientation and <100 nm in size for the multilayer without Ar sputtering pretreatment, while a ~200 nm layer consisting of Al equi-axial nano-crystalline (<10 nm) grains forms between Al columnar grains and underlying TiN film in Al-Cu film for the multilayer with Ar sputtering pretreatment. Both layers of equi-axial and columnar grains are random oriented. Chemical analysis shows a large amount of oxygen and nitrogen segregated in the layer of small equi-axial grains, which is considered to be attributed for the refining of grain size in the layer of equi-axial grain and the degradation of Al(111) texture of Al-Cu film. The mechanism will be proposed for the segregation of oxygen and nitrogen due to the Ar sputtering pretreatment.
4:10 PM		F5-2-9 The Growth Process of some Metallic Films Deposited by Sputtering M. Kawamura, T. Mashima, Y. Abe, K. Sasaki (Kitami Institute of Technology, Japan) The growth process of some metallic films ( of 0.4 nm to 150 nm nominal thickness) by sputtering method was investigated through the characterization of electrical properties, microstructure and crystallite size of the films. To make clear the influence of sputtering conditions on the process, the conditions were varied as follows: target - substrate distance (40 mm or 55 mm), substrate temperature (room temperature, 100°C, 400°C), gas pressure (8 - 20 mTorr) and rf power (25 - 40 W). It is generally known that the electrical resistivity increases with reducing thickness, and an abrupt increse occurs due to the change in films state from continuous to discontinuous. In the case of Pt film deposition, there was negligiable difference on films among various sputtering conditions. And they were continuous state at about 1 nm. This is closely related to the nature of Pt film, which easily grows in 2-dimensional mode. And influence of sputtering conditions is less. However, in the case of Al, thickness where the abrupt increase on the resistivity occurs, very much depended on the sputtering conditions and was from 1 nm to 10 nm. From the results of AFM observation, film deposited under better condition has larger grain size and lower RMS and Ra value. Film deposited on the heated substrate consists of much larger grains, it became continuous state at higher thickness because of the agglomeration. Consequently, influence of the deposition condition on the film growth by sputtering is very much related to the nature of the films.
4:30 PM		F5-2-10 A Numerical Model of Nitrogen Diffusion-precipitation in Low Alloy Iron M. Gouné, T. Belmonte (Laboratoire de Science et Génie des Surfaces (UMR CNRS-INPL-EdF 7570), FRANCE); S. Chomer (Hydromécanique et Frottement, France); H. Michel (Laboratoire de Science et Génie des Surfaces (UMR CNRS-INPL-EdF 7570), FRANCE) The attractive properties of nitrided low alloy steels have long been improved by empirical approach. The combined diffusion/precipitation reaction steps are rather difficult to model. In the case of low alloy iron, elements like titanium, vanadium or aluminium react with nitrogen to form their respective nitrides under the form of a fine dispersion into the matrix. Very few models are available in the literature to describe quantitatively the nitriding process in this case. The purpose of the present work is to provide a realistic description of the phenomena occurring during nitrogen diffusion/precipitation in low alloy iron. A numerical model, based on finite volume method, is used to account for the simultaneous diffusion of nitrogen in ?-ferrite and the precipitation of fine scale nitrides in the diffusion zone. The second Fick's law is coupled to a thermodynamic approach that is used to describe the synthesis of the different metal nitrides formed in the ferritic matrix. Validation of the calculations is performed by considering the example of vanadium containing alloy iron. The calculated nitrogen concentrations in ferrite and alloy element nitride precipitates are provided by the model under various conditions. The nitrogen concentration depth profiles are also given by the model. This model, which describes the precipitation of different possible nitrides in the diffusion zone, can be generalized to iron containing several metallic elements.
4:50 PM		F5-2-11 High Rate and process Control of Reactive Sputtering by Gas Pulsing: Tthe Ti - O Syste, N. Martin, A.R. Bally, P. Hones, R. Sanjines, F. Levy (Ipa, Epfl, Switzerland) Conventional reactive sputtering process with oxygen or nitrogen exhibits nonlinear effects such as hysteresis loops of deposition parameters like the target potential or the reactive gas partial pressure. Such instabilities are usually prevented by implementing particular devices or feedback control systems. In the present paper, we consider an original way to avoid target poisoning by using a well controlled pulsed flow of the reactive gas ^{1, 2}. This reactive gas pulsing technique is used to deposit titanium oxide thin films. Real time electrical characterization of the Ti target and in situ analyses of the reactive atmosphere are currently performed so as to understand and follow kinetics of poisoning and cleaning of the target surface. The effects of the oxygen flow modulation pattern on the deposition rate, structural and morphological properties as well as optical and electrical characteristics of the films are investigated. The pulsing method leads to an increase of the deposition rate (up to 70 % of the pure metal rate) and allows to prepare conductive (σ = 11 S.m^-1 at room temperature) and transparent coatings. Relationships between process parameters like oxygen partial pressure or target poisoning and physical behaviors of the deposited material are discussed. Furthermore, our results suggest that the reactive gas pulsing technique tested with TiO₂ to improve the deposition rate and some properties is also suitable to nitride compounds. ¹ A.J. Aronson, D. Chen and W.H. Class, Thin Solid Films, 72 (1980) 535 ² R.P. Howson, N. Danson and I. Safi, Thin Solid Films, 351 (1999)32.
5:10 PM		F5-2-12 Characterization of 9,10-anthraquinone and 1,4-/1,8-dihydroxy-9,10-anthraquinone Films R.K. Bedi (Guru Nanak Dev Unversity, India); A. Mahajan, A. Singh, R. Kumar, S. Kumar (Guru Nanak Dev University, India) 9,10-anthraquinone; 1,4-dihydroxy-9,10-anthraquinone and 1,8-dihydroxy-9,10-anthraquinone films have been grown by thermal evaporation technique onto the glass substrate kept at different temperatures in a vacuum of 10^-5 torr. The experimental conditions are optimised to obtain better crystallinity of the films. The films so prepared have been studied for their electrical conductivity, carrier concentration, drift mobility, optical properties and electron microscopy. Observations reveal that the electrical conductivity of dihydroxy-9,10-anthraquinone films is more as compared to 9,10-anthraquinone films. The conduction in these films is found to be ohmic in nature. The electrical conductivity and carrier concentration of films increases with the increase in temperature(300-413K), while the drift mobility decreases. The films deposited at higher substrate temperature appear to be more ordered . Results on optical absorption studies indicate the band gap energies in the range of 2.0-3.5 eV. The frequencies of the IR absorption bands for the films are in good agreement with the powder samples taken as reference.