Accurion EP4

Microscopic Thin Film Metrology and Visualization

Accurion EP4 is a high-end system for Imaging Spectroscopic Ellipsometry, combining spectroscopic ellipsometry and optical microscopy in a single instrument. It enables spatially resolved, parallel measurement of film thickness and refractive index on micro-structured samples with lateral resolution down to 1 µm, featuring live ellipsometric contrast imaging and direct selection of regions of interest for quantitative analysis.

The Accurion EP4 redefines imaging ellipsometry by combining Imaging Spectroscopic Ellipsometry, optical microscopy, and spectroscopy in one powerful metrology platform. It delivers precise thin-film metrology and refractive index measurement on microstructures as small as 1 µm, making it ideal for advanced surface characterization and microstructured sample analysis.

The Microscopic Way of Doing Ellipsometry

From Single-Spot Measurements to Imaging Ellipsometry

This evolution from point-based to imaging-based ellipsometry marks a paradigm shift in Thin Film Metrology.

Imaging Spectroscopic Ellipsometry reveals what was previously invisible – local variations of optical properties or film thickness, defects, hidden features etc. The Accurion EP4 sets the benchmark for precise, imaging-based Thin Film Metrology.

Diagram comparing a conventional single-spot ellipsometer with the imaging ellipsometer of the Accurion EP4

Key Features

Superior Performance

• Microscopic lateral resolution down to 1 µm (20x objective or higher)
• Sub-nanometer vertical sensitivity for ultra-thin layers
• Spectral range 190 - 1700 nm
(UV-VIS-NIR)

User Convenience

• Intuitive EP4 software suite (EP4Control, DataStudio, EP4Model)
• Automated sample stage control and large-area stitching
• ROI-based measurement: first identify, then measure

Accessories

• Knife-edge illumination for suppression of back-side reflections
• Modular optical design with interchangeable objective lenses
• Active Vibration Isolation for superior mechanical stability

Real-time Ellipsometric Imaging

The EP4 provides a real-time ellipsometric contrast image, enabling intuitive sample navigation and direct ROI selection. With lateral resolution down to 1 µm, users can quickly identify features of interest and define precise measurement areas within the live view. Imaging Ellipsometry allows “first find, then measure”: relevant microstructures and thin film variations become visible instantly, even before quantitative Δ/Ψ or thickness mapping is performed.

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Principles of Imaging Ellipsometry

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Comparison Imaging and Non-Imaging Ellipsometry

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A tool for studying microstructured samples

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Spectroscopic Imaging Ellipsometry (SIE)

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Applications

Graphene and 2D-material flakes imaged with the Accurion EP4 imaging ellipsometer

2D-Materials

Imaging Spectroscopic Ellipsometry precisely characterizes graphene and other 2D materials. CVD-grown, exfoliated, and epitaxial flakes are analyzed with spatially resolved thickness data.

Silanized and surface-modified layers measured with the Accurion EP4 imaging ellipsometer

Surface Engineering

In surface engineering, imaging ellipsometry studies silanization and surface modification bonding inorganic and organic components, with label-free analysis of layer formation on arrays.

Optical waveguide on a thin film measured with the Accurion EP4 imaging ellipsometer

Photonics

In photonics, spectroscopic ellipsometry measures optical fibers and waveguides at 1 µm lateral resolution. The 190–1700 nm range provides accurate data for development and quality control.

Regions of interest on a display layer stack measured with the Accurion EP4 imaging ellipsometer

Displays

For display materials, the ROI concept enables spectroscopic measurements on micron-scale regions. The UV range to 190 nm determines film thickness, dispersion, and composition in short cycles.

MEMS

The EP4 characterizes MEMS structures down to 1 µm at sub-nanometer thickness resolution. One measurement yields thickness, refractive index, composition, and contamination.

Transparent Substrate

Thin films on transparent substrates are key for flexible displays and optical devices. Knife-edge illumination suppresses backside reflections for non-destructive, artifact-free measurements.

Battery electrode material imaged operando with the Accurion EP4 imaging ellipsometer

Battery Materials

Operando imaging ellipsometry tracks battery electrode materials during charge and discharge. Microscopic Δ and Ψ maps give spatially resolved data, with profile and histogram analysis.

Mueller matrix maps of anisotropic microcrystals measured with the Accurion EP4 imaging ellipsometer

Anisotropic Films

Imaging Mueller Matrix Ellipsometry (IMME) fully characterizes anisotropic thin films and microcrystals, resolving refractive indices and optical axis orientation, as in black phosphorus.

Micro-lens array with anti-reflection coating measured with the Accurion EP4 imaging ellipsometer

Curved Surfaces

The EP4 measures thin films and anti-reflection coatings on flat and curved surfaces. Imaging ellipsometry spatially resolves coating uniformity and defects, particularly on micro-lens arrays.

Protein monolayer spots at a bio-interface measured with the Accurion EP4 imaging ellipsometer

Bio Interfaces

Imaging ellipsometry is sensitive to mono- and sub-monolayer films at bio-interfaces. Micromaps and contrast modes capture dynamic thickness changes, with flow cell or QCM-D accessories.

Air-Water Interface

At the air–water interface, Brewster Angle Microscopy (BAM) visualizes Langmuir–Blodgett monolayers and biomaterials. Molecules, proteins, drugs, DNA, and nanoparticles are studied in situ.

Light Sources

Laser

The EP4 can also be used as a single wavelength ellipsometer with a 658 nm laser as the primary light source.

LED Hub

Six high-power LEDs covering 385–850 nm, ideal for silane coating characterization, DNA spot analysis, and many more.

Grating Monochromator

Continuous spectroscopy from 360–1000 nm, extendable to 190–1700 nm for photonics, display, and 2D material analysis.

Table of the Accurion EP4 light source options and their wavelength ranges

Configuration Possibilities

Like all Park Systems metrology solutions, the EP4 is designed for stability, precision, and intuitive operation. Knife-edge illumination, long-working-distance objective lenses, and a high-stability sample stage work together to minimize measurement artifacts and ensure accurate, reproducible measurements across a wide range of applications.

Objective Lenses

The EP4 uses individually calibrated long-working-distance objective lenses with high numerical aperture: Multiple magnifications are available to ensure the perfect trade-off between resolution and size of Field-Of-View (FOV). All objective lenses cover a spectral range from 360 nm to 1700 nm and can be quickly exchanged. A special UV microscope Objective Lens for wavelengths < 360 nm is available as well.

Stages

A range of manual and motorized sample stages is available to ensure precise sample positioning. Motorized stages allow accurate movement, multi-position pattern measurements, and stitched maps of larger areas, with different stage sizes offered to accommodate various sample dimensions.

Beam Cutter

Transparent substrates, such as glass or silicon at near-infrared wavelengths, can produce unwanted backside reflections that distort ellipsometric measurements. The unique Beam Cutter provides a non-contact optical method to suppress these reflections in a selected region.

Software Suite

The modular EP4 software suite enables intuitive instrument control and online or offline analysis of imaging ellipsometry data through dedicated software modules. EP4Control handles instrument operation and measurement execution, including the definition of measurement parameters and Regions of Interest (ROI) directly in the live ellipsometric view, as well as the acquisition of ellipsometric maps. DataStudio provides tools for visualization and processing of measured data, including map calculation and analysis, spectral clustering, histogram analysis, and cross sections for detailed spatial and spectral evaluation. EP4Model supports optical modeling of thin films and multilayer stacks, enabling the determination of film thickness and optical constants (n, k). Advanced features include effective-medium approximations, modeling of anisotropic materials based on Mueller matrix elements, and access to a comprehensive material database.

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