ICMCTF2006 Session C5: In Situ Monitoring and Control of Optical Film Growth
Tuesday, May 2, 2006 2:30 PM in Royal Palm 4-6
C5-4 Generalized Ellipsometry: Going Beyond Traditional Measurements
J. Jellison, J.D. Hunn, D.E. Holcomb, G.W. Wright, J.S. Baba, C.M. Rouleau (Oak Ridge National Laboratory)
Most ellipsometry experiments are designed to measure the polarization characteristics of an isotropic sample at a large angle of incidence, and the results are often useful in determining optical functions and thicknesses of isotropic thin films, and optical functions of isotropic materials. Anisotropic samples require more sophisticated measurements, often called generalized ellipsometry (GE). In the standard ellipsometric configuration, anisotropic optical properties of materials and thin films can be determined. However, it is also possible to perform these measurements in different configurations, namely in transmission and normal-incidence reflection, and to incorporate microscope optics to dramatically improve spatial resolution. Several examples of GE will be presented: 1) in the traditional configuration, GE can be used to measure optical functions of materials; we will also present a new representation for the pseudodielectric functions of uniaxial materials where the optic axis is aligned with one of the axes of the ellipsometer. 2) In transmission, GE can be used to determine birefringence very accurately, and to monitor internal electric fields in electro-optic materials. 3) In normal-incidence reflection, GE can be used to image preferential orientation of graphite nanocrystals in nuclear fuel particles and small regions of depolarization in defected thin films.@paragraph@ * Research was sponsored in part by the Office of Nuclear Energy, Science and Technology, the Office of Basic Energy Sciences, the National Nuclear Security Administration and Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract No. DE-ACO5-00OR22725.
C5-6 Calculations of Film Thickness for Dip Coated Anti-Reflective Films
L.J. Crawford, N.R Edmonds (University of Auckland, New Zealand)
When applying anti-reflective coatings it is essential to have the correct film thickness, as thickness is the essence of the antireflective film. Thickness can be affected by variables inherent in the coating process, hence prediction of the final film thickness is a necessity. When using the dip or withdrawal method for coating, film thicknesses are affected by the withdrawal speed and the viscosity of the solution. To predict the thickness that is achieved from a solution of known viscosity and known withdrawal speed, modelling theories by Groenveld@footnote 1@ and Yang@footnote 2@ can be utilised. Groenveld derived equations that predict wet film thickness using capillary numbers, withdrawal speed, density, viscosity and surface tension. Yang et al. expanded this theory to enable the prediction of dry film thickness using the same variables. @paragraph@In this study, polymeric anti-reflective films were used to experimentally determine the accuracy of the equations derived by Groenveld and Yang. Other equations have been suggested@footnote 3@ for determining film thickness, but do not take both withdrawal speed and viscosity into account. @paragraph@Experimental thicknesses were measured using atomic force microscopy (AFM), ellipsometry, interferometry and spectral reflectance. The results obtained from the different methods were in agreement with each other, but were approximately 30% lower than the calculated values. @paragraph@@super 1@ Groenveld, P. (1970). "Low capillary number withdrawal." Chemical Engineering Science 25(8): 1259-1266.@paragraph2@super 2@ Yang, C.-C., J. Y. Josefowicz, et al. (1980). "Deposition of ultrathin films by a withdrawal method." Thin Solid Films 74(1): 117-127.@paragraph@@super 3@ Lowy, J. (2004). An Investigation into Amorphous Fluoropolymer Antireflective Coatings for Marine Instruments. Department of Engineering. Auckland, Auckland University of Technology: 141.
C5-7 Development of Multilayer Optics for High Resolution EUV Imaging
T. Hatano, T. Tsuru, M. Yamamoto (Tohoku University, Japan)
We are developing EUV microscope using multilayer optics. The goal of our project is an EUV microscope having spatial resolution of 50 nm, enabling fast imaging of organic and inorganic hybrids, magnetic materials and biological samples. Radiation in the wavelength range of 3 to 30 nm generated from a pulsed laser plasma source will identify specimen constituents by atomic elements such as hydrogen, oxygen, carbon and nitrogen. The microscope optics are reflective, comprising figured multilayer mirrors. We have achieved a technology to control layer thickness over a substrate within an error of 0.4% for reflection wavelength matching. We are also developing a wavefront error correction technology of a 0.1 nm accuracy at a wavelength of 13 nm, being produced by wavefront error measurements with a new EUV interferometer, followed by error correction with a new multilayer milling equipment where a single layer pair removal should be equivalent to a 0.1 nm substrate polish.
C5-9 Ellipsometer Measurements Using Focused and Masked Beams to the Size on the Order of 1000 Nanometers or Less
F.K. Urban, III, D. Barton (Florida International University)
While optical measurements using ellipsometery may be made in air and are non-destructive, the relatively large (> 1mm) spot size has limited their use to surface regions greater than 1 mm in lateral extent. Recent developments in focusing instruments have made spot sizes on the order of 20 to 25 microns possible. The work to be presented explores the use of the 25 micron spot size to probe non-uniform nanostructured thin films. Results of small-spot measurements on 100 micron size manufactured products also will be presented. Further reduction of the spot size is possible using mechanical masking.@paragraph@Measurements have been made to the range of a few microns in width. Finally the practical resolution limits of beam masking will be presented.