VASE J.A. Woollam Co., Inc. Ellipsometry Solutions
Accurate
Capabilities The VASE is our most accurate and versatile ellipsometer for research on all types of materials: semiconductors, dielectrics, polymers, metals, multi-layers, and more. It combines high accuracy and precision with a wide spectral range - 193 to 25nm. Variable wavelength and angle of incidence allow flexible measurement capabilities, including: Reflection and Transmission Ellipsometry Generalized Ellipsometry (Anisotropy, Retardance, Birefringence) Reflectance (R) and Transmittance (T) intensity Cross-polarized R/T Depolarization Scatterometry Mueller-matrix V-VASE Focused Beam Why a VASE? Maximum Data Accuracy The VASE features a rotating analyzer ellipsometer (RAE) combined with our patented AutoRetarder for unparalleled data accuracy. High Precision Wavelength Selection The HS-19 scanning monochromator is designed specifically for spectroscopic ellipsometry. It optimizes speed, wavelength accuracy and light throughput, while automatically controling selection of wavelengths and spectral resolution. Flexible Measurements The V-VASE features a vertical sample mount to accommodate a large variety of measurement geometries including reflection, transmission, and scattering.
Advanced Technology AutoRetarder Technology Rotating Analyzer Ellipsometers (RAE) maximize data accuracy near the Brewster condition - where Ψ/ data are content-rich. However, this region can be limiting for samples with reduced signal. The patented AutoRetarder is a computer controlled waveplate which modifies the light beam polarization before it reaches the sample. This produces optimum measurement conditions for any sample - under any conditions. AutoRetarder accurately measures: Ψ and Δ over the full range! Generalized (anisotropic) Ellipsometry Depolarization data Mueller-matrix data Anisotropy pre-tilt θ Φ (Top) Φ (Bottom) Mueller-Matrix Elements 1..5. -.5-1. 1..5. -.5-1. Model Fit Off-Diagonal MM Data Model Fit Diagonal MM Data 3 5 7 9 11 Wavelength (nm) Mueller-matrix measurement of a super twisted nematic liquid crystal. Glass Substrate ITO Polyimide STN Liquid Crystal Polyimide ITO Glass Substrate 2nm 135nm 3.6 μm 135nm 2nm Twist in Degrees 15 1 5-5.6 1.2 1.8 2.4 3 3.6 Film thickness in microns Generalized Ellipsometry is used to successfully measure anisotropy, twist and pre-tilt of a super twisted nematic liquid crystal fi lm. Twist in Degrees Tilt in Degrees 1 8 6 4 2 Tilt in Degrees
Applications Telecommunications - Laser optics Accurate wavelength selection using monochromator allows measurements at the operating wavelength for optics, e.g. 155nm, 131nm, 98nm, 632.8nm, 589nm Optical Coatings The AutoRetarder measures Δ accurately even when close to or 18 which helps characterize thin films on transparent substrates, such as glass or plastics. Δ in degrees 3 2 1 Coating 23.3μm Thick Films For thicker films (>5 μm), good spectral resolution is needed to resolve the interference oscillation features of Ψ/Δ data. Operator defined monochromator step size and narrow bandwidth help resolve fine spectral features. Ψ in degrees 5 4 3 2 1 Model Fit Exp E 6 Exp E 75 3 6 9 12 15 18 Wavelength (nm) Fine wavelength resolution required for this thick optical coating. Real(Dielectric Constant), ε 1 Imag(Dielectric Constant),ε 2 6 4 2 4 3 2 1 Si Si.6 Ge.4 Si.3 Ge.7 Ge 5 1 15 2 25 Wavelength (nm) SiGe optical constants with varying composition. Semiconductors Bandgap, electronic transitions and critical points can be measured for semiconductor materials such as GaN, InP, SiGe, CdTe, etc. Good wavelength resolution and ability to measure depolarization insure accurate optical constants. Photosensitive Materials The monochromator is positioned before the sample, so only low intensity monochromatic light strikes the sample. This prevents exposure of photosensitive samples. Index of refraction, n 2. 1.9 1.8 1.7 1.6 1.5 193nm 248nm.5.4.3.2.1 1.4. 3 6 9 12 15 18 Wavelength (nm) Optical constants of a photolithography fi lm. n k
Accessories Temperature Control Add cryostat or heat stage for variable temperature studies. Measure samples at both low and elevated temperatures: 4.2 Kelvin to 6 C. Cryostat Imag(Dielectric Constant),ε 2 Real(Dielectric Constant), ε 1 2 15 1 5-5 25 2 15 1 5 Indium Phosphide, 4 Kelvin Indium Phosphide, 297 Kelvin 1. 2. 3. 4. 5. Photon Energy (ev) InP optical constants at 4 Kelvin and room temp. Heat Stage Mapping Provides computer controlled or manual XY mapping of samples of various sizes. Automated sample alignment is also available. Software can automate both acquisition and analysis, as well as plot 3-D graphs.
Liquid Cell Electrochemical Cell Add cell with optical windows for measurement through liquid ambient. Allows characterization of liquid/solid interface. Electrochemical Cell CTAB Thickness in nm 2.5 2 1.5 1.5 -.5 5 1 15 2 25 3-1 Inject CTAB Solution Preliminary Rinse Second Rinse Time in minutes Organic layer thickness deposited from a solution in a liquid cell. Further Options Focusing Camera Sample Rotator (for anisotropy) Flip Down Sample Holder Liquid Prism Cell - LMD
Specifications Spectral Range 25-11nm (single chamber standard) 24-11nm (double chamber standard) DUV extension to 193nm NIR extension to 17nm XNIR extension to >22nm XXIR extension to 25nm V-VASE Angle of Incidence Fully Automated Range: 15-9 (standard system) Accuracy:.1 System Configuration Rotating Analyzer Ellipsometry (RAE) with patented AutoRetarder. Automated wavelength selection via monochromator. Data Acquisition Rate Typical:.1 to 3 seconds per wavelength, depending on reflectivity of sample. High Accuracy: measurements using full AutoRetarder capability require 2 seconds per wavelength.
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J.A. Woollam Co., Inc. 645 M Street, Suite 12 Lincoln, NE 6858 USA Ph. 42-477-751 Fx. 42-477-8214 www.jawoollam.com