Thin film & ellipsometry
Film stacks & optical constants
Thin-film and ellipsometry measurements are spectral inference problems. The information is encoded in wavelength-dependent reflectance, transmission and polarization response, and it can only be recovered if the spectrum is reliable across the whole band the film model uses. Evolve Sensing provides configurable UV, visible, NIR, deep-UV, dual-spectrometer and staged full-range architectures for thin-film and ellipsometry systems.
Typical measurements
Broadband reflectometry
Interference fringes over a wide band from a source that is bright in the visible and weak at both ends. Wavelength accuracy sets thickness accuracy, and dynamic range decides whether the ends of the band are usable.
Spectroscopic ellipsometry
Polarization-sensitive spectra from which the model extracts optical constants as well as thickness. Low stray light and a stable wavelength axis are the decisive specifications.
NIR thickness on thick films
Polymers, organics and thicker semiconductor layers place their useful fringes beyond 1000 nm, often out to 2500 nm, beyond the response of silicon detectors.
Full-range stacks
Multilayer stacks and deep-UV-sensitive surfaces that require 155–2500 nm coverage behind one optical input.
Selection criteria
Specifications that matter in this application
Wavelength range is the simplest part of the specification for these measurements. The following specifications decide the result:
- Dynamic range across a source that saturates in the visible and is weak in the UV and NIR
- Stray light, because the fringe contrast being fitted is small
- Wavelength reproducibility, because every fit assumes a fixed wavelength axis
- Timing and buffering when the spectrometer operates inside a scanning tool
Detector physics
Why staged detectors are used for wide-range film measurement
No single detector performs well from 155 to 2500 nm. Silicon response ends where InGaAs response begins, and a broadband source presents each detector with a different signal level. Staged architectures give each detector the band it is designed for, behind one optical input and one acquisition strategy.
- UV and deep-UV coverage adds sensitivity to very thin layers, surface states and dispersion in the optical constants
- Visible spectrometry covers most standard reflectance and transmission workflows
- NIR coverage captures the information from thicker films, polymers and organics
- A single-input dual-detector NIR architecture splits 900–1700 nm and 1600–2500 nm so each channel has its own integration setting
- A multi-stage system can combine deep-UV, UV-Vis and NIR behind a single input architecture
Timing and acquisition
Timing as part of the film measurement
Inside a tool, a scanning stage or a sequenced source, each spectrum has to correspond to a defined event. Trigger synchronization, batch acquisition, ring buffering and Gigabit Ethernet make the spectrometer part of the tool timing rather than a device polled by software. Ethernet-ready spectrometers → · Wide-range architectures →
Recommended platforms
Instruments suited to this application
These are typical starting points. Send the measurement details and an engineer will confirm the selection or recommend an alternative.
UV-Vis
EagleEye UV-Vis-NIR Spectrometer
High Sensitivity UV-Vis-NIR with a cooled detector
UV-Vis
SmartEngine UV-VNIR Spectrometer
Workhorse UV-VNIR platform with CCD and CMOS sensor options
System
Dual Spectrometer Systems (DS Series)
Integrate two spectrometers with a common trigger for extended range
Also relevant: SideWinder NIR Spectrometer, Phenom High-Resolution Spectrometer, Magna High-Resolution Spectrometer, HummingBird Compact OEM UV-Vis Spectrometer
Scope
Configuration principle
The objective is to collect the right wavelengths with the right detector, dynamic range, timing and calibration, rather than the widest possible range. When a single UV-Vis bench covers the film model, Evolve Sensing recommends the single bench rather than a staged system.
FAQ
Frequently asked questions
- Do I need one spectrometer or a staged system?
- It depends on the wavelength range the film model uses, the signal levels at the ends of that range, the optical geometry and the detector behavior. Broad UV-to-NIR systems usually benefit from staged detectors, and many visible-band workflows do not.
- Why not one very broad-range detector?
- Silicon and InGaAs detectors have different useful ranges, noise, cooling requirements and dynamic-range constraints, and no single array performs both roles well.
- Can Evolve help with OEM ellipsometer integration?
- Yes. Evolve Sensing supports spectrometer selection, triggering, buffering, interface planning and optical configuration, with an evaluation unit available before purchase.
Next step
Discuss your application with an engineer
Send the wavelength range, the sample type and the accuracy required, and an Evolve Sensing applications engineer will recommend a configuration, typically within one business day.