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AVS1997 Session TF-TuP: TF POSTER SESSION

Tuesday, October 21, 1997 5:30 PM in Room Exhibit Hall 1

Tuesday Afternoon

Time Period TuP Sessions | Topic TF Sessions | Time Periods | Topics | AVS1997 Schedule

TF-TuP-1 Plan-View Observation of Al Whiskers in Thin-Film Transistor Metallization K Tsujimoto, S. Tsuji (IBM Japan, Ltd., Japan); K. Kuroda, H. Saka, Y. Suzuki (Nagoya University, Japan) The whisker formation of thin Al films is one of the major concern affecting the yield loss in thin-film transistors fabricated on a glass substrate. To suppress whisker growth, it is necessary to investigate the mechanism of whisker formation. Investigation about the orientation of whisker growth using transmission electron microscopy (TEM) is of great importance to clear the kinetics of whisker formation. Previously we reported the technique for cross- sectional observation of Al whiskers on glass substrates [1]. Here this paper describes a study of plan-view observation on Al whiskers by means of TEM. We successfully prepared plan-view TEM specimens of long and fragile Al whiskers formed in thin Al films on glass substrates. For instance, a kinked whisker having a length approximately 4000 nm could be entirely observed while keeping its original shape. The diameter of this whisker and grain size of thin Al films were approximately 300 nm. The constriction was observed at the whisker/Al film interface, and it was found that this whisker grew different orientation from the original Al grain. We have investigated the crystallographic information of various Al whiskers and individual grains around them in the original Al films. We will discuss the prior orientation of whisker growth. [1] K.Tsujimoto et. al., Proceedings of AVS96, TF-MoP6, 53 (1996).
TF-TuP-2 Electrical Properties of (Pb,La)TiO₃ Thin Films Deposited by Low Pressure Metal-Organic Chemical Vapor Deposition Using Solid Delivery System J.C. Shin, J.M. Lee, S.K. Hong, H.J. Cho, K.S. Kim, H.J. Kim (Seoul National University, Korea); C.S. Hwang (Samsung Electronics Co. Ltd., Korea) Ferroelectric thin films have recently attracted much attention because of their various applications. Among them (Pb,La)TiO₃ thin films especially have been widely applied for DRAM, FRAM and various sensors due to their characteristic ferroelectric properties. However, the growth of high quality multicomponent ferroelectric oxide films by conventional metal-organic vapor deposition technique is very difficult, since solid metal-organic precursors were gradually deteriorated at elevated deposition temperatures and finally could not provide the amount of source vapor enough to produce stoichiometric film. Therefore, the solid delivery system, in which the mixture of the solid metal organic precursors was flash-sublimed into MOCVD growth chamber to obtain a reproducible transport of metal components to film growth surface, was used to deposit (Pb,La)TiO₃ thin films and to control their composition precisely. Pb(TMHD)₂, La(TMHD)₃, and Ti(OiPr)₂(TMHD)₂ solid precursors were chosen to deposit (Pb,La)TiO₃ thin films because it was found from differential scanning calorimetry and thermal gravimetric analysis that they didn't produce any residue and also were deteriorated during deposition. The electrical properties of (Pb,La)TiO₃ thin films were strongly dependent on the substrate temperature, the mixing ratio of metal organic solid precursors, and the input rate of mixture, because the composition, microstructure, and preferred orientation of (Pb,La)TiO₃ thin films were changed with those process parameters.
TF-TuP-3 Ozone Gas Sensors with High Sensitivity using Multicomponent Oxide Thin Films T. Miyata, T. Minami, K. Hashidume (Kanazawa Institute of Technology, Japan) Recently, the detection of ozone gas in ambient air has gained much attention because of concerns over environmental protection. In this paper, we introduce newly developed ozone gas sensors using multicomponent oxide thin films of the ZnO-In₂O₃, MgO-In₂O₃ and Zn₂In₂O₅-MgIn₂O₄ systems. The films were prepared on substrates by conventional r.f. magnetron sputtering. The sensors were operated at temperatures from 200 to 375 °C. The gas sensitivity is defined as the ratio R/R₀; R₀ and R are sensor resistances before and after ozone gas introduction, respectively. All sensors used in this work exhibited an increase of resistance with exposure to ozone gas. The sensing properties of sensors using ZnO-In₂O₃, MgO-In₂O₃ and Zn₂In₂O₅-MgIn₂O₄ films were strongly dependent on the composition in these films. In sensors using MgO-In₂O₃ thin films, a maximum sensitivity was obtained using a film with a MgO content of about 20 mol%. A higher sensitivity was obtained by using a Zn₂In₂O₅-MgIn₂O₄ thin film with a MgIn₂O₄ content of about 80 mol%; at 275 °C, the R/R₀ of this sensor was 14 when exposed to ozone with a concentration of 5 ppm. The increase of resistance is attributed to the trapping of free electrons by O₂ and/or O being adsorbed on grain boundaries and/or the film surface.
TF-TuP-4 Development and Application of Cadmium Stannate and Tin Oxide Transparent Conducting Oxides for CdS/CdTe Photovoltaic Applications. P. Sheldon, X. Wu, X. Li, D.S. Albin, R.G. Dhere, T.J. Coutts (National Renewable Energy Laboratory) Transparent conducting oxides (TCOs) play a critical role in many semiconductor devices. In photovoltaic devices, the TCO serves as the front contact and must be highly transparent with a low sheet resistance to minimize optical and electrical losses. Surprisingly, in recent years, little work has been done to improve the performance of the TCO layer of these device structures. For CdS/CdTe-based photovoltaic devices, conventional TCOs, primarily SnO₂ films, have been used as the front-contact current collector. However, SnO₂ films, deposited using the commercially viable SnCl₄ chemistry, have a resistivity of ~5-8x10^-4 ohm-cm. This yields films with an average transmission of 80% and a sheet resistance of 10 ohms/square. Although this may be adequate for small-area devices and first-generation modules, it does not provide the required design latitude when trying to optimize next-generation devices. In this work, we describe the development and application of several alternate high-performance TCOs optimized for photovoltaic device applications. These include cadmium stannate (CTO) and SnO₂ deposited using a tetramethyltin (TMT) chemistry. The CTO films were prepared by r.f. magnetron sputtering and the SnO₂ films were deposited by low-pressure CVD. Both of these candidates have several significant advantages over conventional TCOs: they are more conductive, more transparent, and have lower surface roughnesses. For example, CTO films have been produced with a sheet resistance of less than 3 ohms/sq. and a peak transmittance of 88.7% (570 nm). These films have resistivities ~6 times lower than SnO₂ films produced using SnCl₄ chemistry and have an average surface roughness that is an order of magnitude lower (Ra = 21 Å). SnO₂ films deposited using the TMT chemistry have also been produced that exhibit superior performance. In this paper, we discuss how these improved TCO properties enhance photovoltaic device performance.
TF-TuP-5 Control of Texture of Polycrystalline AlN Thin Films Deposited on Glass by Collimated Sputtering A. Rodríguez-Navarro, J.M. García-Ruiz (Universidad de Granada, Spain); W. Otaño-Rivera, R. Messier (The Pennsylvania State University) Aluminum nitride (AlN) films were deposited on glass at 15 mtorr using a rf sputtering system. To increase the directionality of the sputtered flux arriving onto the film surface, collimators of angular width varying from 31° to 140° were used. The 3-D crystallographic orientation was studied by the X-ray pole figure method. AlN films develop a (0001). As the angular width of the collimator decreases, the FWHM decreases linearly, indicating a higher alignment of the crystallites inside the sample. For a film deposited with a collimator with angular width of 31°, the FWHM is of 14° compared with 33° when deposited without the collimator. For films deposited with a rectangular collimator, crystallites orient in a fan-like distribution. Another set of AlN films were deposited at different incidence angles of the depositing flux, varying from 0 to 75° from substrate normal, and otherwise identical conditions. In these films, two populations of crystallites can be differentiated. Population-1 crystallites orient with their c-axis pointing to the incoming flux and predominate at low angle of vapor incidence. Population-2 crystallites have their c-axis tilted back about 60° and predominate at high, near grazing, angle of incidence. The alignment of the crystallites, increases with increasing angle of incidence. For films deposited at an incidence angle of 75°, the FWHM of a X-ray phi scan profile is at a minimum of 25°, indicating a high in-plane alignment. These films show six unique maxima in the 10-11 pole figure, showing a complete orientation of the crystallites similar to that of a AlN single crystal. The crystallites align along the [11*0] parallel to the incoming flux. This direction is a channelling direction of the AlN structure and is characterized with a low sputtering yield. The orientation process is due to a selective etching of the misoriented crystal grains, which suffer a higher sputtering yield.
TF-TuP-6 Reactive Species within an Electron Cyclotron Resonance-Microwave Plasma Using Methane as Hydrocarbon Source Gas S.F. Webb, G.A. Gaddy, R. Blumenthal (Auburn University) ECR-microwave plasmas consisting of 4% methane/hydrogen and 4% methane/deuterium are probed using the pulsed supersonic, plasma sampling technique and the results are then compared to determine the identity of the reactive chemical species in the plasmas responsible for diamond deposition. The methane/hydrogen plasmas show a sharp decrease of intensity in the CH_x,(x = 0...4) manifold, accompanied by an analogous increase in intensity in the C₂H_x (x = 0...6) manifold. The largest increase in mass spectral intensity occurs at m/z = 28 corresponding to C₂H₄, lesser increases are observed at m/z = 27 and 26, corresponding to C₂H₃, and C₂H₂ respectively. The signal at m/z = 27 is greater than can be attributed to the cracking of a parent ethylene molecule, and indicates a significant concentration of radical species, C₂H₃, present in the methane/hydrogen plasmas. The methane/deuterium plasmas show a similar decrease in the CH_x,(x = 0...4) manifold, and an increase in the C₂H_xD_y (x + y = 0...6) manifold. The largest increase occurs at m/z = 32, which must be assigned as a fully deuterated ethylene, C₂D₄, since ethane is not observed in the analogous methane/hydrogen plasmas. In a previous study of acetylene/hydrogen(deuterium) plasmas, we observed C₂D₂ to be the major component of the plasma. Through simple statistical modeling, we were also able to show that the observed distribution of species was the result of approximately 6 to 8 reactive steps. The observation of C₂D₄ in the methane plasmas may indicate that deuteration occurs in the CH_xD_y,(x + y = 0...4) manifold. This observation is consistent with less reactive steps occurring in the C₂H_xD_y (x + y = 0...6) manifold.
TF-TuP-7 Characterization of CdTe-In-Cd co-sputtered Films R. Ramírez-Bon, F.J. Espinoza-Beltrán (Universidad de Sonora, México); M. Becerril, O. Zelaya-Angel (CINVESTAV-IPN, México) Indium doped CdTe polycrystalline films and CdTe-In mixed films were grown on Corning glass substrates by co-sputtering from a CdTe-In-Cd target. The elemental In and Cd were glued onto the CdTe target covering small areas. The area covered by elemental Cd was fixed to 1% of the total area of the target, in order to prevent the formation of Cd vacancies in the CdTe lattice. The area covered by elemental In was varied from 1% to 25 % of the target area. The electrical, structural and optical properties of the films were studied as a function of the concentration of both elements. It was found that low In concentration produces an effective doping of the CdTe films. CdTe-In mixed films are obtained for high In concentration.
TF-TuP-8 Sputter Deposition of a YSZ-Based Solid-Oxide Fuel Cell A.F. Jankowski, J.P. Hayes, K.A. Bettencourt, J.D. Morse (Univ. of California - Lawrence Livermore National Laboratory) Solid-oxide fuel cells (SOFCs) are routinely made using bulk ceramic powder processing. Conventional SOFCs are operated at temperatures exceeding 1100 K. A thin film approach demonstrates a method to produce high power densities in a SOFC that operates at temperatures well below 900 K. The thin-film SOFC is deposited using magnetron sputtering. The fuel cell is formed through a continuous deposition process. The anode is first co-deposited by sputtering both Ni and yttria-stabilized zirconia (YSZ). The synthesis continues into the electrolyte layer with only deposition of the YSZ and concludes with co-deposition of the cathode as a Ag-YSZ layer. The SOFC structures are examined in cross-section and plan view. Each layer of the thin film SOFC is less than 1µm in thickness. The current-voltage output from the cell is measured at temperature using hydrogen as the fuel and air as the oxidant. The thin film approach yields an acceptable fuel cell performance but at a through thickness orders of magnitude less than that achievable using conventional ceramic processing. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract #W-7405-Eng-48.
TF-TuP-9 Characteristics of Silicon and Silicon Nitride Etching on Large Area FPD Substrates A. Demos, J.P. Holland (Lam Research Corporation) The etching characteristics of silicon and silicon nitride films deposited large area FPD substrates will be presented. In this work, a planar, inductively coupled, high density plasma source was used to etch these films on substrate sizes up to 600x720 mm. For typical AMLCD processes, high etching rates and good plasma uniformities can be achieved while maintaining good selectivies to the underlying films. The control of etch profiles and linewidths will also be shown to be a function of both etch chemistry and ion bombardment energy. Additionally, methods of achieving selective etching of n+ doped silicon to amorphous silicon will be discussed.
TF-TuP-10 Ion Bombardment Effects on dc Magnetron Sputtered ZnO Thin Films J.H. Shafer, D.J. Dagel, J.R. Doyle (Macalester College) The effects of ion bombardment on the structural and optical properties of ZnO thin films deposited by dc magnetron sputtering are investigated. Plasma is leaked out of the glow region by unbalancing the magnetron magnets. Additional magnets mounted behind the substrate are then used to vary the plasma density in front of the substrate by attracting or repelling the leaking magnetic flux from the target magnets. Langmuir probe measurements indicate that the plasma density at the substrate can easily be varied by more than a factor of ten using this method. An rf bias is applied to the substrate to control the energy of the arriving ions. At floating bias the films have strong preferred orientation along the c-axis normal to the substrate surface as well as good optical transmission at both low and high plasma densities. With increasing substrate bias more random orientation of crystallites is found at high substrate plasma densities, along with decreased optical transmittance implying increasing structural inhomogeneity. Based on these results as well as dependencies on pressure and power a simple kinetic model for the role of energetic bombardment in ZnO film formation is proposed.
TF-TuP-11 Evolution of Microstructure in High Rate Sputter Deposited Al Films J.E. Sanchez, Jr., A.E. Lita, C.J. Wauchope, S.A. Duprey (University of Michigan) The evolution of microstructure of sputter deposited aluminum thin films is fundamentally important in many microelectronic applications. Grain size and crystallographic texture are known to affect processes such as electromigration and stress-induced voiding, hillocking and mechanical yielding in films and patterned lines. Therefore the performance and reliability of structures such as metallization interconnects are dependent on the control of microstructure during processing. However characterizations and understanding of microstructure development during film formation are incomplete. We present the characterization of aluminum grain size, crystallographic texture and surface roughness as they evolve during high rate sputter deposition. Aluminum films were DC magnetron sputter deposited at 1µm/min. at room temperature onto thermally oxidized 150mm Si (100) substrates which were clamped to a water-cooled holder in order to minimize heating during deposition. Al films ranging from 1000Å to 10,000Å in thickness were characterized using transmission electron microscopy (TEM), atomic force microscopy (AFM) and x-ray diffraction (XRD) pole figure analysis. TEM revealed the Al grain structure to be generally columnar, however grain boundaries were commonly inclined through the thickness in the thinnest films. The in-plane grain size was determined by the mean intercept method, and the grain size distribution was lognormal for all thicknesses. It was found that the grain size (d) increased with film thickness (h) at a rate d~h^0.9, where the exponent (0.9) is greater than found previously. Crystallographic texture as determined by x-ray pole figure analysis showed all films had a near-(111) fiber texture, with the (111) peak intensity offset from the film normal by about 5°. The (111) texture quality increased as the film thickness increased. The RMS surface roughness as measured by AFM increased with film thickness, however when normalized by grain size it was found that films became smoother as the film thickens during deposition. These results will be discussed in terms of processes such as surface diffusion and boundary migration which influence the competitive growth between grains of different size, crystallographic orientation and roughness.
TF-TuP-12 The Growth of Eptaxial CoSi₂ using Co/Zr Bilayer on the Different Substrates H. Jeon, D. Kim (Hanyang University, Korea) As devices are scaled down to deep submicron dimensions, a uniform, thermally stable and low resistivity silicides are necessary. Among the metal silicides, CoSi₂ exhibits a special interest because of its lowest resistivity and excellent lattice mismatch with Si, which makes it possible to grow the epitaxial silicide layer on the Si substrates. However, the formation of CoSi₂ using Co metal alone shows polycrystalline texture with rough interface.¹ Epitaxial CoSi₂ can be grown by techniques of molecular beam epitaxy (MBE) and Co/metal layer evaporation. We utilized the Co/Metal layer evaporation method and selected Zr as a metal interlayer because Zr exhibits strong reactivity with oxygen, and small solid solubility with Co.² Therefore we can expect a good quality of epitaxial CoSi₂. In this study we examined the physical and electrical properties of Co-silicide that was formed on the amorphous and crystalline Si substrates. The crystalline substrates were p-type Si(100) and amorphous Si (1000Å) were prepared by CVD method. After Si substrates were cleaned by piranha and HF solution, the Zr (50Å) was deposited in the UHV e-beam evaporator and subsequently the Co (150Å) was evaporated on the different Si substrates. The samples were annealed by RTA in N₂ ambient and vacuum furnace between 500 and 900 centigrade. The samples were analyzed by XRD, SEM, AES, RBS, TEM and 4 point-probe. In our results, the formation temperature of CoSi₂ on the amorphous substrates was lower than that of the crystalline substrates. It is though to be the result of difference of surface energy on the substrates. The qualities of epitaxial CoSi₂ and interface smoothness were improved with increasing temperature. It is assumed that the lateral growth rate of the grain is more rapid than that of the facet as annealing temperature increases. The resistivity in case of crystalline Si was lower than that of the amorphous Si at high temperature while the latter showing lower resistivity at low temperature. ¹S. L. Hsia, T. Y. Tan, P. Smith, and G. E. MaGuire, J. Appl. Phys. 70, 7579 (1991). ²J. S. Byun, J. J. Kim, W. S. Kim, and H. J. Kim, J. Electrochem. Soc. 142, 2805(1995).
TF-TuP-13 The Study on the C49 (TiZr)-Silicide H. Jeon, T. Cha (Hanyang University, South Korea); C. Kim (Korea Research Institute of Standard and Science, South Korea) As semiconductor devices have been densified intensely, the refractory metal silicides have been considered as suitable candidates for contacts and interconnects in very or ultra large scale integrated circuits. Among those silicides, TiSi₂ has been considered as one of the most attractive materials because of its low resistivity and high thermal stability. But its phase transition and agglomeration at high temperature are considered to be the major drawbacks in applying to DRAM devices. TiSi₂ has two structures, that is, metastable C49 (base centered orthorhombic) and stable C54 (face centered orthorhombic) structure. According to previous studies¹ on TiSi₂, the agglomeration was believed to be the result of high surface and interface energy of C54. In this study, Zr was selected to stabilize C49 TiSi₂ and suppress agglomeration of C54 TiSi₂ because Zr and Ti lie in the same column (IVa) showing very similar chemical properties² and moreover, its silicide, ZrSi₂, has only C49 structure with no phase transition. In our experiment, after standard cleaning process, Ti and Zr (~400Å) were co-deposited on Si(100) by dual e-beam evaporator at the base pressure of 10^-6 torr and it was annealed by vacuum furnace and RTA. The amounts of Zr content (10, 50 atomic %) were controlled by deposition rate monitor and the formation of (Ti,Zr) silicide was analyzed by using XRD, SEM, AES, RBS, HRTEM and four point probe. We also used XPS and TEM diffraction pattern to find out whether (Ti,Zr) silicide exists in forms of alloy silicides or separated phases such as TiSi₂ and ZrSi₂. In our results, the transition temperature of TiSi₂ increased with increasing Zr contents. And the agglomeration of silicide was significantly retarded by adding Zr element. The resistivity of the (Ti,Zr) silicide with 50% Zr exhibited lower resistivity than that of 10% Zr at high temperature implying the effect of its agglomeration. 1. H. Jeon, K. J. Yoon, R. J. Nemanich, Thin solid film, (1997, Feb) 2. Y. Dao, D. E. Sayers, and R. J. Nemanich, J. Appl. Physics 78(11) (1995)
TF-TuP-14 Chemical Phase Determination of PZT Surfaces Using Mass Spectroscopy of Recoiled Ions (MSRI)¹ K. Waters, J.A. Schultz, J.C. Holecek, S.R. Ulrich, W.D. Burton, Jr. (Ionwerks); O. Auciello, V.S. Smentkowski, A.R. Krauss (Argonne National Laboratory) The surface analytical method referred to as mass spectroscopy of recoiled ions (MSRI) uses an energetic ion beam to induce a binary collision with species present on a surface. The energy of the binary collision is sufficient to induce complete molecular decomposition. The elemental surface species are ejected from the surface in the forward scattering direction and the ionic species are mass and energy analyzed, providing elemental analysis of the surface being studied. By comparing the positive recoil ion to negative recoil ion yields of various surfaces, we have found that MSRI can be used to characterize the chemical phase of surface species. It is demonstrated that the positive to negative ion ratio of pyrochlore and perovskite PZT surfaces are distinct. Initial results show that the Pb and Zr ± ion ratio changes depending on the surface chemical phase present. Similar observations have been noted for the different BN and carbon surfaces. There is reason to believe that measurements of the positive to negative ion ratio using MSRI may provide a general means of identifying various phases present at the surface. MSRI analysis during film growth film growth at pressures of ≥ 1 mTorr is possible. By measuring the positive to negative ion ratio during film growth, it will be possible to determine (and modify) the phase of the growing film -- during growth. We wish to acknowledge support from NASA SBIR # NAS8-97157 for this work. Additional support to Argonne was provided by ONR, NSF, and the DOE Office of Basic Energy Sciences under contract W-31-109-ENG-38.
TF-TuP-15 Comparison of Sputtered Titanium Nitride on Silicon Dioxide and Aluminum-Alloy Thin Films J.L. Drown (University of Central Florida); S.M. Merchant, M.E. Gross, D. Eaglesham (Bell Laboratories Lucent Technologies); L.A. Giannuzzi (University of Central Florida); R.B. Irwin (Cirent Semiconductor) Titanium nitride (TiN) films are used as anti-reflection coatings (ARC) on aluminum (Al) films to facilitate lithography processes during multilevel metallization for the manufacture of integrated circuits on silicon-based (Si) semiconductor devices. It is generally accepted in the literature that the microstructure of multilevel metal stacks is influenced by the texture of the substrate. For the case of interconnect materials used in the semiconductor industry, a typical metal stack is as follows: Titanium/Titanium Nitride/Al-alloy/ARC-Titanium Nitride. The Ti/TiN layer underneath the Al-alloy film is used as a barrier stack to prevent junction spiking. The Ti/TiN underlayer also determines the growth conditions (crystallography and orientation relationships) of the subsequent Al-alloy film. This study focuses on the microstructural characterization of the ARC-TiN layer on Si-oxide and Ti/TiN/Al-alloy substrates that are fabricated under similar conditions using conventional physical vapor deposition (PVD - sputtering) techniques. The ARC-TiN microstructure was investigated using a variety of analytical techniques. A significant variation in the grain size of the ARC-TiN on the Al-alloy underlayer was observed when compared with that of ARC-TiN deposited on Si-oxide substrates. These differences in ARC-TiN microstructure are important because they affect the electrical and mechanical properties of the stack and have implications for the reliability of the semiconductor device.
TF-TuP-16 Generation of Vapor Stream using Porous Rod in Electron Beam Evaporation Process H. Ohba, T. Shibata (Japan Atomic Energy Research Institute) An evaporation technique with high thermal efficiency in an electron beam evaporation process is presented for the generation of copper vapor. A molybdenum hearth liner and a porous rod made of sintered tungsten with evaporant were set into the water-cooled copper crucible. While the top surface of porous rod was heated by an electron beam which had a power supply of acceleration voltage of 10 kV and maximum emission current of 0.6 A, the molten copper surrounding the rod is transferred by capillarity to the top surface through the pores in rod and then copper vapor stream was generated from there. The vapor properties such as vapor flux, surface temperature profiles, angular distributions, background ion contents, vapor fluctuation and composition were measured with a quartz crystal sensor and a microbalance, a CCD camera, deposited weights, Langmuir probes, a quadrupole mass filter, respectively. The vapor characteristics were compared with the case of use of the bared crucible. The following results were obtained. (1) High vapor flux can be obtained even at low input power since the top surface of rod can be kept at high temperature. (2) Angular distributions at high evaporation rate are able to be described by a simple law of cosⁿθ, except for the extremely high evaporation rate, where n is a rate-dependent beaming exponent and θ is the angle from the vertical. (3) Background ions contained in copper vapor are low. (4) No vapor fluctuation is observed due to the nonexistence of the convective flow and the depression at an evaporation area. (5) The vapor is not contaminated by the porous material.

Time Period TuP Sessions | Topic TF Sessions | Time Periods | Topics | AVS1997 Schedule