Papers

AVS1997 Session VM+MS-MoM: Issues in Scale-Up of Coating Processes and Design of Multifunctional Films

Monday, October 20, 1997 8:20 AM in Room F

Monday Morning

Start	Invited?	Item
8:20 AM		VM+MS-MoM-1 Post Deposition Reduction of Noble Metal Doped ZnO Films G.J. Exarhos, A. Rose, C.F. Windisch, Jr. (Pacific Northwest National Laboratory) When deposited under slightly reducing conditions, transparent ZnO films exhibit both electronic conductivity and infrared reflectivity owing to the introduction of defect electronic states which inject free carriers into the conduction band. Metal cation doping enhances both the conductivity and stability of such films. However, post deposition annealing increases film resistivity through oxidation of the defect states, or reaction of the ZnO matrix either with the substrate or resident dopant. Deposition methods designed to retard these degradative mechanisms are based upon introduction of species more noble than the aluminum, gallium,or indium dopants commonly used to promote film conductivity. Insulating ZnO films containing 2 at. % Al, Ga, Au, Pt, or Cu have been prepared by means of vapor and solution deposition routes under oxidizing conditions. Substantial enhancement in film conductivity is promoted by post deposition reduction in hydrogen above a critical temperature or room temperature cathodic reduction in an electrochemical cell (using aqueous or non-aqueous solvents). Cation dopants such as Au(III) readily can be reduced, but in the reduced state, are difficult to oxidize. Ellipsometry measurements confirm enhanced near infrared absorption owing to the presence of free carriers. Raman spectra reveal a marked broadening of the LO E1 phonon modes which are known to couple to the free carrier states in addition to line intensity enhancement with respect to the allowed E2 modes. XPS measurements probe the chemical state of film dopants in neat and in post deposition reduced or post deposition annealed films. Results suggest that processing methods which introduce oxidatively resistant dopants into the lattice are effective at both enhancing conductivity and film properties stability.
8:40 AM		VM+MS-MoM-2 Development and Scale-Up of a Multifunctional Antireflection Coating, Sputter Deposited on Plastic Film C.I. Bright (Southwall Technologies) A durable, multilayer, electrically conductive antireflection (AR) coating, deposited by vacuum sputtering, was developed on a 340 mm wide, roll-to-roll, laboratory web coating system. The multifunctional requirements for this coating include the following: maximum reflectance of 0.6% luminous and 0.75% average (450 nm - 650 nm), antistatic and electromagnetic interference shielding (300 ohms per square maximum), resistance to fingerprints, stains and chemical attack, durability including adhesion, thermal shock, humidity, salt water immersion, steel wool abrasion and pencil scratch resistance. The developed coating, called AR1, has four optical layers plus a primer layer for bonding to a silica loaded organic hard coating on the flexible polyester (PET) plastic film. Finally, a very thin fluoropolymer layer is deposited from liquid solution, on top of the AR coating, to provide anti-smudge properties and scratch resistance. The coated rolls are cut into sheets, which are bonded to the CRT face of computer monitors to reduce the glare of reflected ambient light. Pilot production quantities of AR1 coating were produced on the narrow laboratory coater. Next the process was scaled-up by modifying an existing 1829 mm wide production web coater. Current high volume production is limited by availability of wide hardcoated PET substrate to 1140 mm in width. These wide web rolls of AR1 coated film are slit to four narrower rolls of 269 mm width, as required for 17" (diagonal) CRT monitors. The evolution of the AR1 coating from design, process development, qualification, scaleup and high volume production is reported.
9:20 AM		VM+MS-MoM-4 Product Manufacturability, Process Scale-up and Technology Transfer D.M. Mattox (Management Plus Inc.) Conceiving, designing and prototyping are the first stages of product development. This is normally done in an R&D environment where the goal is to produce an item with the functional properties that are desired commensurate with the economics. In addition R&D is responsible for developing the process, product and testing specifications and establishing the processing parameter windows. The processes used to produce the item must be capable of being scaled up to the desired production level within the economic constraints. Manufacturability is of concern throughout the initial stages of development and consists of many considerations including patent position, equipment availability, subcomponent availability, raw material availability, environmental concerns, safety, unit cost, and product throughput. Process scaleup requires development of equipment, processes and procedures to give the necessary product throughput and yield. The Manufacturing operation in a company is responsible for producing a quality product within the economic constraints. Technology transfer from R&D into Manufacturing often requires formal and informal communication between persons from two different cultures having different concerns and goals. This paper will discuss the technical and managerial aspects of successful product development, technology transfer and manufacturing. Particular emphasis will be given to the responsibility that the scientist and engineer have in accomplishing this process.
10:00 AM		VM+MS-MoM-6 The Transition to 300mm Silicon Wafer Process Equipment R.Z. Bachrach (Applied Materials) The semiconductor industry is currently in the midst of a transition from 200mm diameter silicon wafers to 300mm wafers for production processing of integrated circuits. Current generation equipment cannot process 300mm wafers and therefore a completely new equipment set is being developed. The various aspects of this scale up will be described, including issues of process technology and equipment productivity. Specific examples will be drawn from Applied Materials equipment for CVD, PVD, ETCH, RTP, HTF, Implant, and CMP as well as some Unique Solutions enabled by Process Sequence Integration.
10:40 AM		VM+MS-MoM-8 Scale-Up for Semi-Conductors of Dual Magnetron Sputtering using Pulsed Power L. Bianchi (FEP-Aultimut) The demand for larger diameter substrate coating equipment producing higher quality films, at faster deposition rates and in production quantities is well known. Dual Magnetron Sputter sources using a double ring structure have been developed as a powerful production tool for the stationary deposition of insulating layers on 6 to 12 inch diameter substrates. This type of sputter source combined with pulsed power techniques (10 to 200 kHz) produce fewer defects on the film, faster deposition rates, and longer production runs. A comparison of defect rates for DC, RF, and pulsed power produced coatings will be given. The faster deposition rates for SiO₂, Al₂O₃, TiO₂ and Si₃N₄ will be given. The use of pulsed power to obtain a longer target life, an arc free coating process, a long term stable coating plasma, and less random coating of the walls will be covered. An example of a double ring, magnetron using a pulsed power unit will be presented. The production of a 40 um thick Al₂O₃ coating in 6", 8" and 12" diameter substrates at a deposition rate of 300 nm/min with a uniform thickness of ± 1% and with zero defects will be discussed.
11:00 AM		VM+MS-MoM-9 Scaling Up of Sputtering Processes to Industrial Dimensions W.D. Münz (Sheffield Hallam University, United Kingdom) Sputtering has been used industrially since the early 1960’s. The large scale production of Ta₂N resistor and B-Ta capacitor networks in telecommunication applications could be considered to be a starting point of an important development. However, two further major inventions were needed, such as the magnetron (in the 70’s), and the unbalanced magnetron (in the 80’s) before a broad breakthrough was achieved. During this lengthy development, a chain of scaling up problems created serious set backs. In particular the change from a two dimensional, to a three dimensional substrate geometry caused serious problems due to the confinement of the gas discharge typical of the conventional planar magnetron. These difficulties were associated with pumping speed, reactive gas and power supply control problems. Today, pulsed power/supply solutions or ‘twin magnetron’ arrangements allow the reproducible deposition of previously sensitive materials, such as aluminium or silicon oxide.
11:40 AM		VM+MS-MoM-11 Real-Time In-Situ Ellipsometric Studies for Rapid Scale-up of TiN Thin Film Growth by Magnetically-Enhanced Reactive Unbalanced Magnetron Sputtering I. Ivanov (University of Nebraska, Lincoln); G. Negrea (Technical University of Cluj-Napoca, Romania); M.L. Kuruppu, D. Thompson, S.L. Rohde (University of Nebraska, Lincoln) Real time in-situ spectroscopic ellipsometry (SE) provides a wealth of information and can be used to facilitate rapid scale-up of deposition processes. SE was used to study how dielectric constants of films vary as a function of growth conditions in reactive unbalanced dc-magnetron discharges using Ar-N₂ gas mixtures. TiN films were grown under widely varying N₂ flows, bombardment energies and neutral-to-ion ratis. Differing ion intensities were achieved using a Helmholtz coil placed behind the substrate platen. Under broad ranging growth conditions, real-time variations in the polarization state of the reflected beam from TiN film surfaces were recorded, and the resulting dielectric constants (ε₁ and ε₂) calculated. For photon energies in the visible range, the behavior was Drude-like. Electrical resistivity ρ was determined by both calculations from ellipsometric data and ex-situ four-point probe measurements. Lower ρ values were obtained at optimum nitrogen gas flow and higher ion bombardment intensity. By increasing ion-to-atom arrival rate ratio at the growing film surface from 0.1 to 1.3 at a constant ion energy of near 20 eV, ρ decreased from 150-200 µΩcm to 26 µΩcm. Good agreement between calculated and measured ρ-values was found for dense films grown at high ion-to atom arrival rate ratios, J_i/J_n = 1.3, while for the lowest J_i/J_n = 0.1 the agreement is not very good. This difference is ascribed to the contribution of structural imperfections (low-density grain boundaries and voids, as observed by TEM) to the free electron transport through these films. These observations correlate well with changes in the stoichiometry of the films, nitrogen consumption, and target state - suggesting that with careful monitoring and process characterization these processes can be scaled-up without extensive re-development.