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J. A. Woollam VASE Spectroscopic Ellipsometer
Variable angle Spectroscopic Ellipsometer
The VASE® is an 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 – up to 193 to 3200nm. Variable wavelength and angle of incidence allow flexible measurement capabilities, including:
- Reflection and Transmission Ellipsometry
- Generalised Ellipsometry (Anisotropy, Retardance, Birefringence)
- Reflectance (R) and Transmittance (T) intensity
- Cross-polarised R/T
- Depolarisation
- Scatterometry
- Mueller-matrix
The VASE features a rotating analyser ellipsometer (RAE) combined with J. A. Woollam patented AutoRetarder for unparalleled data accuracy.
FEATURES
- Standard Spectral Range: 240-1700 nm
- Vertical sample stage with vacuum mount can accommodate up to 200 mm diameter samples (call for custom sample mounting)
- Automated angle of incidence from 15° to 90°
- Double-chamber monochromator for superior stray-light rejection
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OPTIONS
Add camera with display to view spot location on sample. The light beam may not appear on smooth, specular surfaces.
Commonly sold with Standard or Alternate Focusing
Translator Size: 150×150 mm XY
Standard stage and Translation stage are swappable.
Translator Size: 50×50 mm XY
Includes two exchangeable stages.
Open stage with hole for transmission mapping (41×41 mm)
Standard stage and Translation stage are swappable.
Commonly sold with Alternate Focusing
100 or 200 μm beam diameter depending on installed optical fiber.
Commonly sold with Camera
200 or 400 μm beam diameter depending on installed optical fibre.
Commonly sold with Camera and 50×50 mm Automated Translation.
Temperature range: 4.2 to 500 Kelvin OR 4.2 to 800 Kelvin
Angle: 70°
Includes UHV chamber/cryostat, turbo pump,and temperature controller.
Cryostat can be installed and removed, which allows the user to switch between the standard sample stage and the cryostat.
Temperature range: -70°C to 600°C
Angle: 70°
Active Cooling with Liquid Nitrogen
Sample area 22mm in diameter
Temperature range: Room Temp to 300°C
Angle: 70°
Passive Cooling
Sample area up to 50mm diameter
Automated high precision sample rotation (360° Theta-only) stage.
Useful when studying anisotropy. Through-hole behind sample allows transmitted beam measurements from normal incidence (0°) to ±19°.
Standard stage and rotation stage are swappable.
Translator Size: 50×50 mm XY
Standard stage and Manual Sample Translation stage are swappable.
The liquid minimum deviation cell is used to determine liquid refractive index (n and k) using a hollow prism cell. Measure minimum deviation angles through the liquid filled prism. Two cells are included:
- 6 mL (60° angle of incidence)
- 5 mL (30° angle of incidence)
Features Automated Z-Translation
General purpose liquid cell with vertical mount above liquid line for convenient electrochemical work.
General purpose liquid cell with 5mL volume
Ultra low-volume liquid cell. (Minimum sample size 8 mm x 21 mm)
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Applications
Photovoltaics
Film thickness and optical properties are critical to performance of solar devices. Ellipsometry is used for development and monitoring of all PV materials: a-Si, μc-Si, poly-Si, AR Coatings (SiNx, AlNx), TCO Films (ITO, ZnOx, doped SnO2, AZO), CdS, CdTe, CIGS, organic PV materials, and dye sensitised films.
Optical Constants
Thickness measurements are not independent of the optical constants. The film thickness affects the path length of light travelling through the film, but the index determines the light waves’ velocity and refracted angle. Thus, both contribute to the delay between surface reflection and light travelling through the film. Both n and k must be known or determined along with the thickness to get the correct results from an optical measurement.
Laser Optics
Accurate wavelength selection using monochromator allows measurements at the operating wavelength for optics, e.g. 1550nm, 1310nm, 980nm, 632.8nm, 589nm.
Thin Films
The film thickness is determined by interference between light reflecting from the surface and light travelling through the film. Depending on the relative phase of the rejoining light to the surface reflection, interference can be defined as constructive or destructive. The interference involves both amplitude and phase information.
Chemistry/Biology
The M-2000 can be used for a variety of chemical and biological applications, either as a stand-alone tool or in combination with one of our many accessories. Study materials under liquid ambient, at high or low temperatures, or in conjunction with QCM-D measurements.
Conductive Organics
Great progress has occurred in the area of organic layers and stacks used for display (OLED) or photovoltaic applications. There are many different materials being studied, from small molecules such as Alq3 to conjugated polymers such as P3HT. Often multiple materials are blended together – which requires the wide spectral range of the M-2000 – to probe different wavelengths where the organics are optically different. Long-chain molecules may also have significant anisotropy, where orientational stacking of the polymer chains produces different optical constants in different directions.
Semiconductors
Traditional ellipsometry applications are still going strong. Characterise any semiconductor material: resists, photomasks, SiON, ONO stacks, low-k dielectrics, high-k gates, SOI, SiGe, II-VI and III-V ternary and quaternary compounds.
Lithography
Lithography thin films were an important motivation for the VUV-VASE® development. It has been successfully used to characterise all types of films in this area, including Photoresists and Bottom and Top AR Coatings.
Metamaterials & the Meta-6 Layer
For ellipsometry, we usually consider only the electric-field component of the electromagnetic (EM) wave interaction with the material. We ignore the interaction of the magnetic-field component because atoms and molecules tend to have a weak magnetic response to EM waves at optical frequencies. Thus we usually consider only dielectric response (permittivity) and ignore magnetic permeability. However, certain kinds of metamaterials change all of that. Metamaterials consist of an artificially-created array of small structures or particles, usually smaller than the measurement wavelength. These structures or particles can be considered “artificial atoms” or “meta-atoms”, with properties tailored to interact with incoming EM waves in ways generally not observed in naturally occurring materials.
