Recent Advances in Optical and Polymer Film Technology
Monday, April 10, 2000 1:30 PM in Room Sunset
C2-1 Supersonic Molecular Jet Epitaxy: Thin Film Growth Using Hyperthermal Kinetic Energy Neutral Molecules
G. Eres (Oak Ridge National Laboratory)
The arriving flux and the incident kinetic energy, along with the condition of the substrate are important variables that determine not just the growth rate, but the structure and the composition of thin films grown by chemical vapor deposition. The incident kinetic energy can be used to alter the rate, or the outcome of particular reaction pathways, to synthesize a material with properties that are different than those produced by equilibrium film growth processes. Reducing the epitaxial growth temperature is another potential benefit that is particularly important for optical material and semiconductor thin films. The significance of supersonic molecular jets stems from the fact that both the arriving flux and the incident kinetic energy of neutral growth species can be varied independently. It is significant that the kinetic energy can be varied in the range that is sufficient to break chemical bonds, but it is still below the threshold for causing lattice damage. The number of studies that explore these advantages in a wide range of material systems is growing rapidly. In this paper the effects of both superthermal incident kinetic energy and flux on the growth and properties of elemental and compound semiconductor thin films will be discussed.
C2-3 Development of Large Diameter Radical Beam Sources
T. Murata (National Institute of Materials and Chemicals Research, Japan); S. Matumoto (Shincron Co., Ltd., Japan); Y. Yamada, H. Nozoye (National Institute of Materials and Chemicals Research, Japan)
Plasma assisted deposition methods have been widely used so far to synthesize varieties of thin. However, charged particles such as electrons and ions, which are inevitably included in plasma, hit surfaces of thin films while the films are being deposited and deteriorate the characteristics of films. High density radical beam sources have attracted attention because it can avoid these problems mentioned above and afford a new deposition method to deposit high quality thin films at relatively low substrate temperatures. @paragraph@ We have been developing radical beam sources with beam diameters larger than 100mm intending to enhance the productivity of thin films. In this study, an end plate with small orifices was set at the end of a quartz discharge tube to maintain the gas pressure inside the discharge tube high while keeping the pressure inside a deposition chamber low. It has been widely known that dominant species of inductive coupling plasma change from ionic species to radical species when the pressure of the plasma gas in a discharge tube is changed from ca.0.1 Pa to 1-100 Pa. Oxygen plasma was generated inductively by a RF (13.56 MHz) power supply. The appropriate conditions to generate high intensity radical beams were surveyed systematically by changing the diameter and number of turns of the coil, the strength of magnetic field supplied to the discharge tube, shapes of the tube and so on. In particular, when the shape of the discharge tube was changed from a tubular shape to a flat shape the intensity of the radical beam was doubled. Furthermore, the ratio between the intensity of radical species and that of charged species from the radical beam source could be controlled by changing the shapes of the end plate. @paragraph@ We will report the detailed experimental results of the high performance radical beam sources.
C2-4 Reflection Enhancement of Aluminum Strips by EB-PVD in Highly Productive Industrial Lines
E. Reinhold, J. Richter, H. Waydbrink, E. Zschieschang (Von Ardenne Anlagentechnik Gmbh, Germany)
In recent years the improvement of energy efficiency has become an urgent issue in the industrial countries. Reflector materials with enhanced reflectivity open up the possibility of increasing the lighting efficiency in order to economize the illumination energy.@paragraph@Meanwhile large area coating of aluminum strips by EB-PVD in order to achieve enhanced optical reflectivity of up to 96 % has been established by industry for the purpose of reflector mass production. The reflection increasing layer system consisting of the 3 layers aluminum, silicon dioxide and titanium dioxide is coated on aluminum strips which are up to 1250 mm wide. The latest production start of such a new air-to-air coating line allowing strip speeds of at least 20 m/min has occured some months ago.@paragraph@The process management of the individual EB-PVD process steps and the ellipsometrical online layer measurement at the moved strip will be presented. The highly productive air-to-air coating line for long time deposition cycles of up to 120 production hours without interruption will be introduced. Finally the paper will analyze coating results on anodized as well as lacquered strips and discuss tendencies of product development.
C2-5 Enhanced Pulsed Reactive Sputtering Using an Inductively Coupled Plasma Source
P.J. Kelly, P.S. Henderson, R.D. Arnell (University of Salford, United Kingdom); D. Carter, G. Roche (Advanced Energy Industries)
The pulsed reactive sputtering process, in conjunction with reactive gas feedback control systems, now allows the routine deposition of high quality dielectric films. Pulsing the magneton discharge in the mid-frequency range (20-350kHz) prevents arc events at the target and stabilises the deposition process. Feedback control of the reactive gas, using an optical emissions monitor for example, establishes constant conditions at the target, allowing control to be maintained at any point on the hysteresis curve. In many cases, however, it has been found that the optimum properties for films, such as alumina, are obtained when the target is operated in at least a partially poisoned mode. This has a detrimental impact on the deposition rate of the film and can lead to long-term stability problems during deposition. An alternative approach, aimed at overcoming these problems, is to introduce pre-activated oxygen into the chamber via an independent plasma source. @paragraph@ In this study, an inductively coupled plasma (ICP) source has been used to generate activated oxygen for introduction into an otherwise standard closed field unbalanced magnetron sputtering system. A number of alternative mounting arrangements for the ICP unit have been considered. The total flow of reactive gas into the chamber is divided between a piezo valve, which forms part of the feedback control loop, and the ICP. Operating in this manner allows transparent, stoichiometric alumina films to be deposited whilst maintaining the target in a metallic mode. This paper, therefore, compares the ICP enhanced process with the standard deposition process, both in terms of operating parameters and film properties.
C2-7 Low Temperatuere Deposition of Optical Coatings using Ion Assistance
H. Niederwald (Carl Zeiss, Oberkochen, Germany)
Ion assisted deposition of optical coatings has been studied for many years at a scientific level. Progress in ion source technology and in process control has lead to industrial application and to the introduction of ion- and plasma-assisted coating technologies into the production of optical components. A special advantage is for example the deposition of durable coatings without addition of thermal energy, which opens a number of new applications on temperature sensitive substrates. This talk will give an overview over recent developments, will deal with the different technologies used, their major applications and will summarize possible benefits as well as drawbacks which are inherent (or not?) in ion- or plasma-assisted optical coating technology.
C2-9 Structural Investigation of Plasma Polymerized Coatings Deposited by an r.f. ICP Source
A. Vanhulsel, E. Dekempeneer (VITO, Belgium); J.P. Celis (Katholieke Universiteit Leuven, Belgium)
Plasma polymerized amorphous coatings have been deposited by means of a planar magnetically confined inductively coupled r.f. plasma (ICP) source. An interesting example from the viewpoint of applications are amorphous fluorocarbon (a-C:H:F) coatings. In former work, these coatings have been deposited and characterized as hydrophobic and anti-smudge topcoats for display applications. In this study, the correlation between deposition conditions and structural properties of ICP plasma polymer coatings have been investigated. Two coating types have been dealt with: fluorine and silicon alloyed carbon coatings. FEG-SEM and AFM were used to study the coating morphology and initial stages of growth. Investigation of the chemical structure at the surface was performed by XPS, while the bulk of the coatings was investigated by FTIR and NMR spectroscopy. For the a-C:H:F coatings, a discrepancy was revealed between XPS depth profiling and NMR results. Depth sensing indentation was used to measure the hardness and modulus of elasticity. The surface energy was derived from contact angle measurements.
C2-10 Thin Film Polymer Coatings for Multiple Applications
M. Mikhael, A. Yializis, W. Decker (Sigma Technologies International, Inc.)
The Polymer Multi-Layer Process (PML) is a high speed deposition process to coat surfaces with functional polymer coatings. The process, which is based on acrylic polymers, is widely used in thin film capacitor and barrier film applications. Meanwhile a number of specialty acrylates with a wide range of bulk and surface properties have been formulated, which broaden the use of the PML process for many applications. Adjustable surface energy and hydro- and olio-phobicity and -philicity, a wide range of optical indices and dielectric coefficients, photoconductive and static dissipative coatings are just some of the properties of acrylic polymers that can be used in the PML process. This talk will present the main properties of these specialty formulations and their applications in the industrial field.
C2-11 The Potential of Organic Light Emitting Devices for Display Applications
P.E. Burrows, S.R. Forrest (Princeton University); M.E. Thompson (University of Southern California)
We review recent results from small molecule organic light emitting devices (OLEDs) and their implications for full color organic displays. Until recently, light emission from OLEDs utilized the radiative recombination of singlet excitons, either formed directly on the dye molecules or transferred from the host molecules by Forster energy transfer. This intrinsically limits the internal quantum efficiency of OLEDs to ~ 25%, since ~ 75% of electrically injected charge carriers form non-emissive triplet excitons. Optical losses in the OLED reduced the maximum achievable external quantum efficiency to ~ 5%. The development of organic electrophosphorescence using organic dyes such as iridium tris(phenylpyridine) (Ir(ppy)3) has led to dramatically increased device efficiencies. Spin-orbit coupling via the heavy metal ion in such molecules mixes the singlet and triplet states, potentially allowing radiative recombination of 100% of the electrically generated excitons. Using Ir(ppy)3-based OLEDs, we have demonstrated phosphorescence at an external quantum efficiency of > 10% and luminous efficiency of > 30 lm/W. Effects unique to phosphorescent devices, such as output saturation due to triplet-triplet interactions, will be discussed. We also describe recent results from transparent OLEDs (TOLEDs), using sputter-deposited indium tin oxide (ITO) cathodes to achieve > 70% pixel transparency at low operating voltage. The application of phosphorescent TOLEDs to three dimensional pixel architectures for high efficiency, full color flat panel displays will be discussed.