ICMCTF2005 Session B9: Pulsed Plasmas for Vapour Depositions

Friday, May 6, 2005 8:30 AM in Room San Diego

Friday Morning

Start	Invited?	Item
8:30 AM		B9-1 Enhanced HIPPMS Thin Film Growth using Secondary Magnetic Field Discharge Confinement S.L. Rohde, S. Chennadi, S. Sevvana, J. Li, R.K. Lakkaraju, D.M. Mihut (University of Nebraska) Using High Powered Pulsed Magnetron Sputtering, HPPMS (alternatively, HIPIMS), peak plasma densities >1013 cm-3 have been observed. These values are roughly three orders of magnitude higher than conventional sputtering, and as a result sputtered metal ionization increases. Some reports indicate ionization levels as high as 70-90%, compared with 5-10% in conventional magnetron sputtering. While the ionization fraction in HPPMS is significantly higher, the overall deposition rate observed in most HPPMS studies is significantly lower than (~30%) conventional magnetron sputtering. In the present study, the ionization efficiency and deposition rate of HPPMS has been investigated as a function of secondary magnetic confinement of the discharge in the substrate region. Using an internally mounted Helmholtz coil to provide additional magnetic confinement, significant increases in deposition rate were observed. Two configurations were explored, one with the coil making a closed-loop arrangement with the outer pole of the cathode and two, the reverse orientation. The two configurations resulted in deposition rates that varied by as much as 40% depending on the configuration and field strength of the coil. Other variables investigated included coil current, substrate bias and working gas composition. In addition, an effort was made to determine what, if any, effects the discharge confinement had on film uniformity. The present study provides evidence that more conformal coatings could be made on complex workpieces using HPPMS processes, and that measurable rate improvements can be achieved using secondary magnetic confinement.
8:50 AM		B9-2 Innovative Solutions for Wear Protection of Tools and Components Using Bipolar Pulsed PVD (H.I.P^TM) Toni Leyendecker, O. Lemmer, R. Cremer, G. Erkens, H.-G. Fuss (CemeCon AG, Germany) Owing to the constantly increasing requirements regarding modern cutting tools, the established wear protection coatings like TiN or TiCN, for example, are no longer in a position to cover all current areas of application for coated tools. Even the most advanced wear protection coatings come to their limits in applications like high-speed cutting or dry processing, for example. One of the principal reasons for the limited performance of these coatings is the high thermal and oxidative stress to which the coating is subjected in the aforementioned applications. Through new bipolar pulse technology one is today in a position to deposit conducting and insulating coatings of almost any stoichiometry. Moreover, through extremely dense plasmas which now can be produced, also the deposition of crystalline high-temperature modifications is possible. This was enabled through the use of bipolar pulsed plasmas and a new kind of arrangement within the vacuum chamber, which guides the dense plasma to the substrate in a well directed manner (coating system CC800cirlce with R/9). Highest plasma ionisation, optimum performance for insulating coatings, nanocomposites, perfect surfaces and optimised deposition rates are the result.
9:10 AM	Invited	B9-3 Recent Progress in High Power Impulse Magnetron Sputtering A.P. Ehiasarian (Sheffield Hallam University, United Kingdom) High power impulse magnetron sputtering (HIPIMS) is an emerging technology for the physical vapour deposition of coatings and substrate pretreatment. HIPIMS relies on a short duration (impulse) gas discharge reaching high peak power densities of 3000 Wcm^-2 at current density of 1-4 Acm^-2. Within the duration of each pulse the discharge develops from a gas-dominated to a metal-ion dominated state as the plasma density reaches peak values in the range of 10¹³cm^-3. A combination of gas and self-sputtering mechanisms are operational. HIPIMS plasmas contain significant proportions of singly and doubly charged metal ions whose relative densities are determined by the peak power of the discharge. Applications of HIPIMS have been successful for substrate pretreatment to enhance adhesion whilst maintaining a macroparticle-free coating microstructure. The combination of the two factors has strongly improved the tribological and corrosion performance of conventional-magnetron sputtered CrN layers in comparison to glow discharge and arc discharge pretreatments. Functional layers deposited by HIPIMS have shown fully dense microstructures formed under deposition fluxes with high ion-to-neutral ratios. Advanced hardware design is now available for the industrialisation of HIPIMS to cathode areas of >1000 cm².
9:50 AM	Invited	B9-5 Low Temperature Functional Film Synthesis on Polymer by Pulsed Magnetron Sputtering J.G. Han (Sungkyunkwan University, South Korea) Functional film metallization on polymer sheet becomes increasingly applied in emerging digital electronics and flexible packaging materials and devices. The prime issue in metallization on polymer substrate is the control of process temperature to avoid damage of temperature sensitive polymer materials. In addition the synthesis of compound films including oxides and nitrides of high temperature phase on polymer is often hard to be resolved in conventional magnetron sputtering process. Pulsed magnetron sputtering process is a prospective way to overcome barriers in such thin film synthesis at low temperature. This paper discusses on the nucleation and growth behavior on a few polymer substrates at various plasma conditions by modulating pulse duty and frequency in pulsed magnetron sputtering. The surface temperature evolution is designed by theoretical modeling in terms of plasma parameters including particle flux and energy and compared with empirical data measured by in-situ monitoring of film surface temperature with specified IR measurement system at various pulsed power input conditions. The modulation of film microstructure and stress with temperature evolution is then achieved by control of plasma parameters with a variation of pulse conditions, which are illustrated with integrated diagnostics data measured by Langmuir probe, nano-second time resolved optical emission spectroscopy and laser absorption spectroscopy. Finally a couple of application of functional film synthesis on polymer by pulsed magnetron sputtering method is illustrated with theoretical process design and empirical results at low temperature range of 50 to 100°C.
10:30 AM		B9-7 The Effect of Pulse Sequence Modulation and Pulse Energy on Structural Coating Properties and Coating Composition L. Lugscheider, K. Bobzin, M. Maes (Aachen University, Germany) Ever increasing tool and machine part performance require novel coatings and have led to the demand for complex, fine grained structures and a graded composition of PVD coatings in order to fulfill the high demands. Pulsed power supplies offer an excellent opportunity to deposit non-conductive, high quality coatings with outstanding deposition rates. Many papers report a positive effect of higher ionization and increased plasma density. In this paper bipolar power supplies with a duplex, dual cathode arrangement were used to vary coating composition and generate a graded layer in industrial coating equipment. For this purpose the pulse sequence and energy was altered during deposition. The coating process was analyzed by both plasma diagnostics as well as common thin film analytics.
10:50 AM		B9-8 Reactive Co-Deposition of TiN_x/SiN_x Nanocomposites using Pulsed dc Magnetron PVD P. Sunal, M.W. Horn, R. Messier (Pennsylvania State University) In order to understand the degree of control over nanocrystalline composite thin film properties using pulsed-DC sputter deposition, the pulsing frequency was varied and the resulting film properties characterized. Nanocrystalline-TiN/a-Si_xN_y films were reactively deposited using an asymmetric bipolar pulsed dc power supply. The thin films were co-sputtered from pure Ti and Si targets over the mid-frequency range of 50-200 kHz. The plasma potential, ion density, and electron temperature have been determined using a Langmuir probe and compared to results of an energy resolved mass spectrometer. Agreement of the plasma potential between the two techniques shows the bombardment of the growing films changes with frequency. Using nanoindentation, the mechanical properties of the films are studied and related to the plasma properties during deposition. Finally, the plasma properties were studied against the sputter pressure. At higher pulsing frequencies, the plasma potential increases causing energetic bombardment which yields smaller nanocrystal diameters, less than 5nm, with stoichiometries approaching unity for TiN and 3:4 for Si_xN_y.
11:10 AM		B9-9 Single-Target DC-Pulsed Deposition of Lead Zirconate Titanate Thin Films: Investigation of the Chemical and Mechanical Properties by Glow-Discharge Optical Emission Spectroscopy and Nanoindentation A. Fischer, R. Thapliyal (Swiss Federal Laboratories for Materials Testing and Research (EMPA), Switzerland); M. Amberg (Swiss Federal Laboratories for Materials Testing and Research (EMPA), St. Gallen, Switzerland); H.-J. Hug (Swiss Federal Laboratories for Materials Testing and Research (EMPA), Switzerland); D. Hegemann (Swiss Federal Laboratories for Materials Testing and Research (EMPA), St. Gallen, Switzerland); P. Schwaller, M. Aeberhard (Swiss Federal Laboratories for Materials Testing and Research (EMPA), Thun, Switzerland); T. Nellis, J. Michler (Swiss Federal Laboratories for Materials Testing and Research (EMPA), Switzerland) Lead zirconate titanate (PZT) thin films are currently researched for memory applications, MEMS, sensors and transducers¹. Due to the growing interest in wearable computing, the need for industrial scale deposition of PZT has further increased. PZT can be grown by sol-gel, laser ablation, and CVD, but in particular PVD is a promising tool to produce PZT thin films with improved properties. Although much focus has been placed on the excitation mode², target design³, as well as post annealing conditions⁴, a real breakthrough in low-cost deposition processes for industry has not been achieved. The goal of the present work is the development of multicrystalline PZT films deposited either on Si wafers or on optical fibers. Prior to PZT deposition, a top coat with the layer sequence Ti/Pt(111)/Ti was applied on the substrates. For the first time, a single metallic target with the composition (at%) Pb(55)Zr(22.5)Ti(22.5) was sputtered in an Ar/O₂ atmosphere using pulsed DC. The morphological, structural, chemical and mechanical properties of coated specimens deposited at different substrate temperatures and post-annealed either in a tubular oven or by rapid thermal annealing (RTA) at different temperatures were investigated. Emphasis was placed on the determination of the mechanical properties investigated by nanoindentation and nanoscratch techniques. Quantitative depth profiling for the determination of the chemical composition of PZT thin films was used for the first time with pulsed glow discharge optical emission spectroscopy (Pulsed-GDOES) The method for PZT deposition on wafers was adapted for optical fiber coating and results are discussed. ¹ J. F. Scott et al., Science 246 (1989) 1400 ² S. Yamauchi, et al.; Integrated Ferroelectrics 14 (1997) 159 ³ T. Hata et al.; Vacuum 51 (1998) 665 ⁴ C.V.R Vasant Kumar et al., J. Appl. Phys, 71 (1992) 864.
11:30 AM		B9-10 Phase Separation and Formation of the Self-Organized Layered Nanostructure in C/Cr Coatings in Conditions of High Ion Irradiation P.Eh. Hovsepian, Y.N. Kok, A. Ehiasarian (The Sheffield Hallam University, United Kingdom); R. Haasch, J.G. Wen, I. Petrov (University of Illinois at Urbana Champaign) C/Cr coatings were deposited by the Arc Bond Sputtering technique, at wide range of bias voltages, Ub from -65 to -550 V. Plasma diagnostics carried out by electrostatic probe measurements revealed that C/Cr films grow under conditions of intensive ion bombardment with ion-to-neutral ratio exceeding J_i / J₀= 6. Under these conditions the high diffusion mobility and the reactivity of the C leads to distinct changes in the coatings microstructure and phase composition. Raman spectroscopy and XPS analysis of the films showed that the phase composition of the films gradually transforms from more graphite like (sp² C-C bonded) to more Me-carbon (Cr-C bonded), where the content of the carbide phase increases with increase of the bias voltage to Ub = - 350V and higher. In parallel HRTEM employing HAADF imaging revealed that the microstructure evolved from columnar with carbon accumulated at the column boundaries (Ub= -65V, - 95V) to a structure dominated by onion like C-Cr clusters (Ub= -120V), which than converts to a distinct nanoscale layered structure (Ub= -350V, - 450V), finally transforming to a uniform fine grain structure at Ub= -550V. The new nanoscale layered structure forms via ion irradiation induced self-organisation mechanism. It is characterized by abnormally large values for the bi-layer thickness of 20 nm and 25 nm, that are not related to substrate rotation, for films grown at Ub= - 350V and Ub= - 450V, respectively. ADF STEM imaging and quantitative EELS analysis showed that the nanoscale multilayer structure comprises of alternating layers of Me-carbide phase (48%C, 52%Cr) and almost pure C (91.34%C), where the bias voltage defines the bi-layer thickness. A coating growth model accounting for the deposition and the resputtering rates as well as the influence of the ion bombardment on the C diffusion rate in the growing C/Cr film is proposed to explain the phase separation and formation of the self-organised layered nanostructure.
11:50 AM		B9-11 Reactive AC Pulsed Magnetron Sputtering of Magnesium Oxide Thin Films C. Peters, U. Krause, T. Kopte (Fraunhofer Institut fuer Elektronenstrahl- und Plasmatechnik, Germany); H. Kupfer, R. Kleinhempel, F. Richter (TU Chemnitz, Germany); Y. Cheng (Carnegie Mellon University) High quality MgO thin films for PDP applications have been successfully prepared by a reactive dual-magnetron sputter technology using a sine wave power supply. The magnetron sources were equipped with Mg targets with a length of 400 mm. The layers were deposited onto silicon as well as onto float glass substrates under various conditions in the oxide and the transition mode. The influence of the oxygen flow rate on the structure and properties of the films were systematically studied at a constant Ar flow rate (120 sccm) and a constant total pressure (0.4 Pa). The microstructure and mechanical properties of the films were investigated by X-ray diffraction, stress measurement and atomic force microscopy. Furthermore, the results of measured secondary electron emission and sputter yield of the MgO films will be presented. The samples prepared in the transition mode show a very low optical absorption of about k = 10^-4 and a refractive index of about 1.74, which nearly equals the bulk value. The high mass density of 3.5 g cm^-3 was measured by neutron reflectometry. The structural properties are discussed in terms of the adatom mobility, which is mainly influenced by the oxygen partial pressure. The high secondary electron emission coefficient up to 0.1 and a low sputter yield of about 0.2 in combination with a high deposition rate of 35 nm m min^-1 support the capability of the films for the application in Plasma Display Panels. An up-scaling to a target length of 900 mm qualifies this deposition process as an industrial deposition technology.
12:10 PM		B9-12 Oxidation Behavior of Polycrystalline CrN/AlN Multilayer Coatings Fabricated by Pulsed DC Magnetron Sputtering J.G. Duh, S.-K. Tien (National Tsing Hua University, Taiwan); C.-W. Lee (Dong Nan Institute of Science and Technology, Taiwan) CrN/AlN multilayer coatings with modulation periods in the range between 5 nm and 30 nm were fabricated on the silicon (001) substrate by Pulsed DC magnetron sputtering technique. The input power of both Cr and Al target was fixed at 300W with the pulsed frequency of 20 kHz to eliminate the surface contamination on the target. The modulation periods of the multilayer coatings was further evidenced by the transmission electron microscopy (TEM). To evaluate the oxidation behavior of CrN/AlN multilayer coatings, the CrN and CrN/AlN coatings were studied by the thermo-gravimetric analysis (TGA) which was isochronally heated from room temperature to 1000°C and isothermally annealed for 1 h at elevated temperature. Auger electron sperctroscopy (AES) was used to reveal the elemental distributions of these coatings. It is found that the multilayer CrN/AlN exhibited a superior anti-oxidation behavior compared to the CrN single layer. Furthermore, the oxidation resistance of multilayer CrN/AlN coating with modulation period of 5 nm was higher than that with larger modulation period.