By J.A. Woollam
For the VASE and VUV-VASE, this involves our patented AutoRetarder before the sample. Woollam spectroscopic ellipsometers cover the spectral range from 33 microns to 140nm. This range offers an incredible flexibility that can meet almost any application requirement.
The IR-VASE® is the first and only spectroscopic ellipsometer to combine the chemical sensitivity of FTIR spectroscopy with thin film sensitivity of spectroscopic ellipsometry. The IR-VASE covers the wide spectral range from 1.7 to 30 microns (333 to 5900 wavenumbers). It is used to characterize both thin films and bulk materials in research and industry. This rapidly growing technology is finding uses in the optical coatings, semiconductor, biological and chemical industries, as well as research labs. OVERVIEW Why an IR-VASE Mark II? Wide Spectral Range Covers near to far infrared. 1.7 to 30 microns (333 to 5900 wavenumbers) Resolution from 1cm -1 to 64cm -1 High Sensitivity to Ultra-thin Films Spectroscopic ellipsometry data contain both “phase” and “amplitude” information from reflected or transmitted light. The phase information from IR ellipsometry offers higher sensitivity to ultrathin films than FTIR reflection/absorbance, while retaining the sensitivity to chemical composition. Non-destructive Characterization The IR-VASE offers non-contact, non-destructive measurements of many different material properties. Measurements do not require vacuum, and can be used to study liquid/solid interfaces common in biology and chemistry applications. No Baseline or Reference Sample Required Ellipsometry is a self-referencing technique that does not require reference samples to maintain accuracy. Samples smaller than the beam diameter can be measured because the entire beam does not need to be collected. Highly Accurate Measurement Patented calibration and data acquisition procedures, provide accurate measurements of Ψ and Δ over the full range of the instrument. The IR-VASE can determine both n and k for materials over the entire spectral range from 1.7 to 30 microns without extrapolating data outside the measured range, as with a Kramers-Kronig analysis. Perfect for thin films or bulk materials including dielectrics, semiconductors, polymers, and metals. APPLICATIONS Optical Coatings Characterize thickness and IR index of single and multilayer films. Bulk uncoated substrates. Infrared optical systems. AR, HR, single-layer and multilayer coatings. High-index and low-index. Molecular Bond Vibrations Like standard FTIR spectroscopy, IR ellipsometry relies on the information about molecular bond vibrations. Infrared absorption caused by these vibrations can be studied in bulk or thin film materials. IR ellipsometry offers increased sensitivity over FTIR spectroscopy. It also presents the advantage of obtaining both n and k rather than just absorbance values. Figures below show measured optical constants of a silicone thin film with vibrational absorptions labeled. Multilayer Characterization Multilayer films can be extensively studied using the wide spectral range and variable angle capability of the IR-VASE®. Multiple angles provide additional information by changing the light’s path length through each layer. The following results show sensitivity to 3 layers. Infrared optical contrast between similar materials allows measurement of each layer’s thickness. Chemical Composition Via Molecular Bond Vibrational Absorptions Like standard FTIR spectroscopy, IR ellipsometry contains information about molecular bond via vibrational absorptions. Infrared absorption caused by these vibrations can be studied in bulk or thin film materials. IR ellipsometry offers increased sensitivity over FTIR spectroscopy. It also obtains both n and k rather than just absorbance. Figures below show measured optical constants of a silicone thin film with vibrational absorptions labeled. Epitaxial Layers, Doping Concentration and Doping Profiles At infrared wavelengths, the difference in free-carrier levels can cause optical contrast between epitaxial or implanted layers. This gives IR-VASE® excellent sensitivity to epitaxial layer thickness and substrate doping concentration. The ellipsometer also has good sensitivity to carrier gradients at interfaces. Carrier profiles show near-perfect in agreement when nondestructive IR-VASE® and destructive SIMS measurements are compared. Phonon Structure (Compound Semiconductors) The Wide spectral range IR-VASE® is important for phonon absorption studies. Data on the left show phonon modes of a GaN / AlGaN laser structure, modeled to determine alloy ratios, doping concentrations, and film quality. SPECIFICATIONS Ellipsometer Configuration RCE Wavelength Range 1.7μm to 30μm 333cm-1 to 5900cm-1 Resolution 1cm-1 to 64cm-1 (user defined) Detector DTGS Angles of Incidence 32° to 90° Data Acquisition Rate (Complete Spectrum) 1 to 30 minutes, typical (1 angle of incidence at 16cm-1 resolution) Finer resolution will require longer time. Max substrate thickness 20mm Facility Requirements Please contact J.A. Woollam Co. for complete list of facility requirements. Dimensions ACCESSORIES Temperature Control +Cryostat (4.2/77 to 500 Kelvin or 4.2/77 to 800 Kelvin) +Basic Temperature Stage (room temp to 300°C) +Standard Temperature Stage (-70°C to 600°C) Sample Mounting Options +Sample Rotator +Manual Sample Translation (50x50mm XY) RESEARCH Publications “Application of IR variable angle spectroscopic ellipsometry to the determination of free carrier concentration depth profiles” Authors: H. Arwin, A. Askendahl, P. Tengvall, D.W. Thompson, J.A. Woollam Thin Solid Films, 313-314, (1998) 661-666. “Determination of the Mid-IR Optical Constants of Water and Lubricants Using IR Ellipsometry Combined with an ATR Cell” Authors: T. Tiwald, D. Thompson, J. A. Woollam, and S. V. Pepper Thin Solid Films, 313-314, (1998) 718-721. “Carrier concentration and lattice absorption in bulk and epitaxial silicon carbide determined using infrared ellipsometry” Authors: T.E. Tiwald, J.A. Woollam, S. Zollner, J. Christiansen, R.B. Gregory, T. Wetteroth, S.R. Wilson, A.R. Powell Phys. Rev. B, 60, 16, (1999) 11464-11474. “Infrared dielectric anisotropy and phonon modes of sapphire” Authors: M. Schubert, T.E. Tiwald, C.M. Herzinger. Phys. Rev. B, 61, 12, (2000) 8187-8201. “Free-carrier and phonon properties of n- and p-type hexagonal GaN films measured by infrared ellipsometry” Authors: A. Kasic, M. Schubert, S. Einfeldt, D. Hommel, T.E. Tiwald Phys. Rev. B, 62, 11, (2000) 7365-7377. “Infrared ellipsometry studies of thermal stability of protein monolayers and multilayers” Authors: H. Arwin, A. Askendahl, P. Tengvall, D.W. Thompson, J.A. Woollam physica status solidi (c), 5, 5, (2000) 1438-1441. “Use of Molecular Vibrations to Analyze Very Thin Films with Infrared Ellipsometry” Authors: H. G. Tompkins, T. Tiwald, C. Bungay, and A. E. Hooper J. Phys. Chem. B, 108, 12, (2004) 3777-3780. “Toward Perfect Antireflection Coatings. 3. Experimental Results Obtained with the Use of Reststrahlen Materials” Authors: J. A. Dobrowolski, Y. Guo, T. Tiwald, P. Ma, and D. Poitras Applied Optics, 45, 7, (2005) 1555-1562. FAQ What changes were made between the original IR-VASE and current Mark II version? The Mark II is smaller; it requires less benchtop space and uses less purge gas. The globar light source and scanning laser inside the FTIR are designed for longer lifespan. The Mark II is also easier to construct and service. Performance advantages include shorter optical path length and smaller measurement spot size. Which software package is included? WVASE
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The iSE is a new in-situ spectroscopic ellipsometer developed for real-time monitoring of thin film processing. Using our proven technology, the iSE enables users to optimize optical properties of deposited films, control film growth with sub-angstrom sensitivity, and monitor growth kinetics. OVERVIEW Why an iSE? Powerful With the power of spectroscopic ellipsometry (SE), the iSE is capable of measuring thickness and optical properties with much higher certainty than other techniques. Compact New compact design enables easy integration onto any chamber. Versatile Accurately determines thickness and optical properties for wide variety of thin films including metals, semiconductors, oxides, nitrides, and more. Affordable The power of spectroscopic ellipsometry at a reasonable price. Easy-to-Use User-friendly interface for real-time analysis of thin film growth and etch. ADVANTAGES Fast, Wide-Spectrum Measurements The iSE utilizes a new optical design with Dual-Rotation™ in combination with modern CCD detection to provide hundreds of wavelengths in a fraction of a second. Dual-Rotation enables continuous, multi-zone measurements with unparalleled accuracy and capability. Dynamic spectroscopic ellipsometry data is graphed at four representative wavelengths. Each measurement versus time actually consists of 190 wavelengths from ultraviolet to near infrared. A few time points are graphed above, showing the SE data before, during, and after film growth. High Sensitivity: Ellipsometry measurements over a wide spectral range provide sensitivity to a variety of material properties such as composition, conductivity, surface conditions, etc. In addition, ellipsometry is sensitive to thickness changes at the sub-angstrom level. Real-Time: Monitors changes in film thickness and optical properties during deposition. Use these measurements for feedback control. Non-Destructive: In-situ SE uses light to probe the thin film in a noninvasive manner. The ellipsometer is outside the process chamber and light is allowed to enter through windows and interact with the sample. The light beam directly measures surface of interest without any damage or need for special sample preparation. Accurate: SE measurements calculate the change in polarization of light. For real-time measurements, this has significant advantages over intensity-based measurements: • Data accuracy is not affected by coated windows • Collects accurate data even without collecting the entire beam • Polarization contains phase measurements which are highly sensitive to very thin films (Left) ALD film growth increasing in the first 25 cycles of deposition shown alongside changes in the raw ellipsometry data. (Right) Optical properties and thickness of a metallic film changing as a function of deposition time. Common Real-Time Ellipsometry Measurements • Thin film thickness from single or multiple layers • Growth or etch rates • Process kinetics • Optical constants • Surface quality before and after processing • Film nucleation behavior • Process conditions that affect optical constants (deposition rate, temperature, pressure, etc.) • Real-time end-point detection Efficient Process Characterization A common application of real-time SE involves monitoring an entire series of thin films during a single process. Each film is produced with varying conditions, which enables a quick understanding of the deposition process. Optical constants and growth rate are determined from each layer to characterize the process. In-situ SE data (only two wavelengths) is shown above. The process varied between different film types and different process conditions. In this manner, a multi layer structure was characterized with information obtained from each individual film. The optical constants and growth rate were determined for both Ta and a-Si films versus varying deposition conditions. SPECIFICATIONS Ellipsometer Type Dual-Rotation™ Optical Design Wavelength Range 400-1000 nm Number of Wavelengths 190 Detector CCD Data Acquisition Rate 0.3 sec. [Fastest] 1-2 sec. [Typical] Beam Diameter ~3mm Chamber Requirements Port Size: 1.33” or 2.75” Typical Port Angle: 60°-75° measured from sample normal FAQ Is chamber pictured included? The vacuum chamber shown in the photos is for demonstration purposes only. The iSE designed to work with many different types of vacuum chambers. What is included? Source and Receiver Control Box Tilt Stage Mounts Calibration Base 2.75” Optical Viewports What data types can the iSE measure? Spectroscopic ellipsometry, advanced generalized-SE or Mueller Matrix-SE Which software package is included? CompleteEASE
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The M-2000® line of spectroscopic ellipsometers is engineered to meet the diverse demands of thin film characterization. An advanced optical design, wide spectral range, and fast data acquisition combine in an extremely powerful and versatile tool.The M-2000 delivers both speed and accuracy.Our patented RCE technology combines Rotating Compensator Ellipsometry with high-speed CCD detection to collect the entire spectrum (hundreds of wavelengths) in a fraction of a second with a wide array of configurations.The M-2000 is the first ellipsometer to truly excel at everything from in-situ monitoring and process control to large-area uniformity mapping and general purpose thin film characterization.No other ellipsometer technology acquires a full spectrum faster. Why an M-2000? Advanced Ellipsometer Technology: The M-2000 utilizes our patented RCE (rotating compensator ellipsometer) technology to achieve high accuracy and precision. Fast Spectral Detection: The RCE design is compatible with advanced,proven CCD detection to measure ALL wavelengths simultaneously. Wide Spectral Range: Collect over 700 wavelengths from the ultraviolet to the near infrared – all simultaneously. Flexible System Integration: With modular optical design, the M-2000 is suited for direct attachment to your process chamber or configured on any of our table-top bases. Accuracy: Advanced design ensures accurate ellipsometry measurements for any sample. Applications: The M-2000® is a versatile spectroscopic ellipsometer, suited to many different sample types. Coatings can be dielectrics, organics, semiconductors, and even thin metals. Optical Coatings: Characterize both thickness and refractive index for single- and multi-layer coatings;anti-reflection, high-reflection, or decorative coatings. Calculate the color coordinates for your coating stack under different lighting conditions. 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. Characterize 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. 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 sensitized films. Transparent conductive oxides appear metallic at long wavelengths and dielectric in the visible. The M-2000 can gather info about the film from both of these regions. In-Situ: The M-2000 is ideal for in-situ monitoring and process control. It is used successfully with a number of different processes to provide real-time results: MBE Sputter ALD E-beam evaporators, MOCVD PECVD Plasma etch ECR, Liquid Cells Temperature Stages Cryostat Specifications: Ellipsometer Configuration: Rotating Compensator Ellipsometer (RCE) Spectral Range: D: 193-1000 nm; X-210: 210-1000 nm; X: 245-1000 nm; U: 245-1000 nm; V: 370-1000 nm; +NIR: adds 1005-1690 nm Number of Wavelengths: D ~500; X-210 ~485; X ~470; U ~470; V ~390; +NIR adds ~190 wavelengths Detector: CCD Angles of Incidence: 45°-90° (Automated Angle Base); 20°-90° (Vertical Automated Angle Base); 65° (Fixed Angle Base); 65° (Test Base) Data Acquisition Rate (Complete Spectrum): 0.05 seconds, minimum; 2-5 seconds, typical Max substrate thickness: 18mm Power Requirements: 100/240 VAC, 47-63Hz, <1 Amp Dimensions: Contact us for dimensions Accessories: Sample Translation/Rotation: Horizontal base options: +Automated XY (100x100mm, 200x200mm, or 300x300mm); +Manual XY (50x50mm); +Automated Sample Rotation. Vertical base options: +Automated XY (50x50mm); +Manual XY (50x50mm); +Automated Sample Rotation Temperature Control: +Basic Temperature Stage (room temp to 300°C); +Standard Temperature Stage (-70°C to 600°C); +High Temperature Stage (room temp to 1000°C); +Cryostat (4.2/77 to 500 Kelvin or 4.2/77 to 800 Kelvin) Liquid Studies: Horizontal base options: +5mL Liquid Cell; +500uL Liquid Cell; +2mL Electrochemical Cell; +5mL Heated Liquid Cell; +500uL Variable Temperature Liquid Cell. Vertical base options: +45mL Electrochemistry Compatible Cell; +270uL Liquid Cell; +5mL Liquid Cell Focusing & Camera: Add focusing optics to decrease the measurement beam diameter. Focusing optics are detachable for normal use. Add a camera to view the measurement spot on the sample and improve beam positioning. Contact us for details. FAQ: Is automated mapping included? The M-2000 is highly customizable. We offer several options for automated mapping. Is table included? The table pictured is an optional feature convenient for containing computer and electronics. Can the M-2000 be used in situ? Yes. Modular source and receiver can be attached to chamber. Which software package is included? CompleteEASE What is the difference between M-2000 and RC2? The M-2000 was the first widely-used high-speed ellipsometer. It has a long history of success in research and production, and it’s optical design includes a single rotating compensator. The RC2 is a newer design with many of the same great features combined with innovative new technology. Further, it has two rotating compensators, which allow measurement of the full Mueller-matrix.
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The RC2® design builds on 25 years of experience. It combines the best features of previous models with innovative new technology: dual rotating compensators, achromatic compensator design, advanced light source and next-generation spectrometer design. The RC2 is a near-universal solution for the diverse applications of spectroscopic ellipsometry. Why an RC2? Advanced Measurement Capabilities The RC2 is the first commercial spectroscopic ellipsometer to collect all 16 elements of the Mueller matrix. Mueller matrix SE allows characterization of the most advanced samples and nanostructures. Best Measurement Accuracy Advanced measurement capabilities allow the best accuracy from fast CCD-based ellipsometry. Dual Rotating Compensators Synchronous rotation of two compensators provides high accuracy, high speed, and complete Mueller-matrix measurements. Achromatic Compensator Design New achromatic compensator design with optimized performance over a wide spectral range. patent pending Wide Spectral Range Collect over 1000 wavelengths from the ultraviolet to the near infrared – all simultaneously. Fast Measurement Speed Synchronous operation of both compensators allows highly accurate data without waiting to "zone-average" over optical elements. Collect the entire spectrum (over 1000 wavelengths) simultaneously in a fraction of a second. Advanced "Dual" Light Source Dual light source for extended spectral range with computer control of beam intensity. Automatically optimize signal on any sample (low or high reflection). ANISOTROPY APPLICATIONS Generalized Ellipsometry Traditional ellipsometry measurements are ideal for standard thin film characterization. However, more advanced measurements are required for anisotropic materials. Generalized Ellipsometry collects six values compared to the standard two (Ψ, ∆). This additional information completely characterizes the cross-polarization of anisotropic samples. Generalized Ellipsometry Measures: Anisotropic PEN (Polyethylene Naphthalate) Generalized Ellipsometry measurements of the transmitted beam provide high sensitivity to the birefringence in anisotropic PEN films. Variable Angle Generalized Ellipsometry was used to fully characterize the biaxial indices (n x ≠ n y ≠ n z) of the PEN substrate. Complete Mueller-matrix The RC2 can characterize the full Mueller-matrix of a sample. This advanced data type insures appropriate characterization of complex samples that are both anisotropic and depolarizing. Viewing the entire Mueller matrix allows access to different polarization effects in advanced samples. The yellow and green sections are related to Diattenuation and Polarizance, respectively. The red section shows unrotated Retardance. Further rotating the sample will shift this information into different regions of the Mueller matrix. Rotation MM-SE scan shows the retardation signature from an anisotropic sample in the bottom-right nine elements. Liquid Crystal Twisted nematic liquid crystal films introduce the complexity of an anisotropic film with a smoothly varying optical axis. With the thick liquid crystal layer sandwiched between glass substrates, the Mueller-matrix measurements insure the best measurement. The complete Mueller-matrix was measured for a twisted liquid crystal. This enabled characterization of the optical axis twist and pre-tilt, and liquid crystal anisotropic refractive index. SPECIFICATIONS Ellipsometer Configuration Dual RCE Wavelength Range D / X / U / +NIR / +XNIR: 193-1000 nm / 210-1000 nm / 210-1000 nm / adds 1005-1690nm / adds 1005-2500nm Number of Wavelengths D / X / U / +NIR / +XNIR: ~800 / ~790 / ~790 / adds ~275 wavelengths / adds ~250 wavelengths Detector CCD Angles of Incidence: 45°-90° (Automated Angle Base); 20°-90° (Vertical Automated Angle Base); ~65° (Focused Base); 65° (Fixed Angle Base); 65° (Test Base) Data Acquisition Rate (Complete Spectrum): 0.3 seconds, minimum; 2-10 seconds, typical Max substrate thickness 18mm Power Requirements 100/240 VAC, 47-63Hz, <1 Amp Dimensions Contact us for dimensions ACCESSORIES Sample Translation/Rotation Horizontal base options: - Automated XY (100x100mm, 200x200mm, or 300x300mm) - Manual XY (50x50mm) - Automated Sample Rotation Vertical base options: - Automated XY (50x50mm) - Manual XY (50x50mm) - Automated Sample Rotation Temperature Control - Basic Temperature Stage (room temp to 300°C) - Standard Temperature Stage (-70°C to 600°C) - High Temperature Stage (room temp to 1000°C) - Cryostat (4.2/77 to 500 Kelvin or 4.2/77 to 800 Kelvin) Liquid Studies Horizontal base options: - 5mL Liquid Cell - 500uL Liquid Cell - 2mL Electrochemical Cell - 5mL Heated Liquid Cell - 500uL Variable Temperature Liquid Cell Vertical base options: - 45mL Electrochemistry Compatible Cell - 270uL Liquid Cell - 5mL Liquid Cell Focusing & Camera Add focusing optics to decrease the measurement beam diameter. Focusing optics are detachable for normal use. Add a camera to view the measurement spot on the sample and improve beam positioning. Contact us for details. FAQ Is automated mapping included? The RC2 is highly customizable. We offer several options for automated mapping. Is table included? The table pictured is an optional feature convenient for containing computer and electronics. Can the RC2 be used in situ? Yes. Modular source and receiver can be attached to chamber. Which software package is included? CompleteEASE What is the difference between M-2000 and RC2? The M-2000 was the first widely-used high-speed ellipsometer. It has a long history of success in research and production, and it’s optical design includes a single rotating compensator. The RC2 is a newer design with many of the same great features combined with innovative new technology. Further, it has two rotating compensators, which allow measurement of the full Mueller-matrix.
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