VASE®

J.A. Woollam Co., Inc.Ellipsometry Solutions

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 2500nm. Variable wavelength and angle of incidence allow fl exible measurement capabilities, including:

• Refl ection and Transmission Ellipsometry • Generalized Ellipsometry (Anisotropy, Retardance, Birefringence) • Refl ectance (R) and Transmittance (T) intensity• Cross-polarized R/T• Depolarization• Scatterometry• Mueller-matrix

materials: semiconductors, dielectrics, polymers, metals, multi-layers, and more. It combines high accuracy and precision with a wide spectral range - 193 to 2500nm. Variable wavelength

Capabilities

Why a VASE?Maximum Data AccuracyThe VASE features a rotating analyzer ellipsometer (RAE) combined with our patented AutoRetarder®

for unparalleled data accuracy.

High Precision Wavelength Selection The HS-190™ scanning monochromator is designed specifi cally for spectroscopic ellipsometry. It optimizesspeed, wavelength accuracy and light throughput, while automatically controling selection of wavelengths and spectral resolution.

Flexible MeasurementsThe V-VASE features a vertical sample mount to accommodate a large variety of measurement geometries including refl ection, transmission, and scattering.

Focused Beam

V-VASE

Advanced Technology

AutoRetarder® TechnologyRotating 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

AutoRetarderRotating 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

Generalized Ellipsometry is used to successfully measure anisotropy, twist and pre-tilt of a super twisted nematic liquid crystal fi lm.

pre-tilt θ

Φ (Top)

Φ (Bottom)

Anisotropy

Mueller-matrix measurement of a super twisted nematic liquid crystal.

Wavelength (nm)300 500 700 900 1100

-1.0

-0.5

0.0

0.5

1.0

Model Fit Diagonal MM Data

-1.0

-0.5

0.0

0.5

1.0Model Fit Off-Diagonal MM Data

Mue

ller-

Mat

rix E

lem

ents

Glass Substrate

Glass Substrate

ITO 20nmPolyimide 135nm

STN Liquid Crystal 3.6 µm

Polyimide 135nmITO 20nm

-50

0

50

100

150

0 0.6 1.2 1.8 2.4 3 3.6Film thickness in microns

Twis

t in

Deg

rees

0

2

4

6

8

10

Tilt in Degrees

Twist in DegreesTilt in Degrees

Telecommunications - Laser opticsAccurate wavelength selection using monochromator allows measurements at the operating wavelength for optics, e.g. 1550nm, 1310nm, 980nm, 632.8nm, 589nm …

Photosensitive MaterialsThe monochromator is positioned before the sample, so only low intensity monochromatic light strikes the sample. This prevents exposure of photosensitive samples.

Thick FilmsFor 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.

Optical CoatingsThe AutoRetarder® measures Δ accurately even when close to 0° or 180° which helps characterize thin films on transparent substrates, such as glass or plastics.

SemiconductorsBandgap, 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.

Applications

Wavelength (nm)0 500 1000 1500 2000 2500Im

ag(D

iele

ctric

Con

stan

t),ε 2

0

10

20

30

40SiSi0.6Ge0.4Si0.3Ge0.7Ge

Rea

l(Die

lect

ricC

onst

ant),

ε1

0

20

40

60

Fine wavelength resolution required for this thick optical coating.

Wavelength (nm)0 300 600 900 1200 1500 1800

Inde

x of

refra

ctio

n, n

1.40

1.50

1.60

1.70

1.80

1.90

2.00

0.00

0.10

0.20

0.30

0.40

0.50

nk

193n

m24

8nm

Wavelength (nm)300 600 900 1200 1500 1800

Ψin

deg

rees

10

20

30

40

50

Model Fit Exp E 60°Exp E 75°

∆in

deg

rees

0

100

200

300

Coating 23.3µm

SiGe optical constants with varying composition.

Optical constants of a photolithography film.

Accessories

MappingProvides 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.

Temperature ControlAdd cryostat or heat stage for variable temperature studies. Measure samples at both low and elevated temperatures: 4.2 Kelvin to 600° C.

Temperature ControlAdd cryostat or heat stage for variable temperature studies. Measure samples at both low and elevated temperatures: 4.2 Kelvin to 600° C.

Cryostat

Heat Stage

-5

0

5

10

15

20

Photon Energy (eV)1.0 2.0 3.0 4.0 5.00

5

10

15

20

25

Indium Phosphide, 4 Kelvin

Imag

(Die

lect

ricC

onst

ant),ε 2

Rea

l(Die

lect

ricC

onst

ant),

ε1

Indium Phosphide, 297 Kelvin

InP optical constants at 4 Kelvin and room temp.

Liquid CellElectrochemical CellAdd cell with optical windows for measurement through liquid ambient. Allows characterization of liquid/solid interface.

Further OptionsFocusingCameraSample Rotator (for anisotropy)Flip Down Sample HolderLiquid Prism Cell - LMD™

Electrochemical Cell

-1

-0.5

0

0.5

1

1.5

2

2.5

0 5 10 15 20 25 30

Time in minutes

CTA

B Th

ickn

ess

in n

m

Inject CTABSolution

PreliminaryRinse

SecondRinse

Organic layer thickness deposited from a solution in a liquid cell.

Specifi cations

Spectral Range250-1100nm (single chamber standard)240-1100nm (double chamber standard)DUV extension to 193nmNIR extension to 1700nmXNIR extension to >2200nmXXIR extension to 2500nm

System Confi guration Rotating Analyzer Ellipsometry (RAE) with patented AutoRetarder®. Automated wavelength selection via monochromator.

Angle of IncidenceFully AutomatedRange: 15°-90° (standard system)Accuracy: 0.01°

Data Acquisition Rate Typical: 0.1 to 3 seconds per wavelength, depending on refl ectivity of sample.High Accuracy: measurements using full AutoRetarder capability require 20 seconds per wavelength.

V-VASESpectral Range250-1100nm (single chamber standard)240-1100nm (double chamber standard)DUV extension to 193nmNIR extension to 1700nmXNIR extension to >2200nmXXIR extension to 2500nm

System Confi gurationAnalyzer Ellipsometry (RAE) with patented AutoRetarderwavelength selection via monochromator.

Angle of IncidenceFully AutomatedRange: 15°-90° (standard system)Accuracy: 0.01°

Data Acquisition RateData Acquisition RateTypical: 0.1 to 3 seconds per wavelength, depending on refl ectivity of sample.Typical: 0.1 to 3 seconds per wavelength, depending on refl ectivity of sample.THigh Accuracy: measurements using full AutoRetarder capability require 20 seconds per wavelength.