Thin Film Thickness: Methods, Conditions and Product Ranges
Thin film thickness is the physical or model-derived distance associated with a deposited layer. The correct measurement approach depends on the film stack, material response, substrate, surface, sample geometry and required output. This guide separates general measurement principles from the specifications published for current TDM products.
What Thin Film Thickness Means
A film is called “thin” relative to its application and the physical effects being controlled. Thickness can influence optical interference, electrical transport, stress, adhesion and barrier behavior, but those relationships are material- and structure-dependent. A percentage change in thickness should not be presented as the same percentage change in device performance without application data.
State whether the requested value is physical thickness, optical thickness, wet-film thickness, step height or a model-derived layer thickness. These quantities can require different sensors, calibration samples and reporting assumptions.
Units and Required Test Conditions
- 1 micrometer (µm) = 1,000 nanometers (nm).
- 1 nanometer (nm) = 10 ångströms (Å).
- Record the film/substrate stack, nominal range, sample size, spot size, environment, measurement mode and repeat count with every result.
- Keep repeatability, absolute accuracy, resolution and detection limit separate; they are not interchangeable specifications.
General Thin Film Thickness Measurement Methods
The method overview below is educational. It does not imply that TDM currently sells every listed technique, and it intentionally avoids universal range or accuracy numbers because those depend on the instrument, material, model and test condition.
| Method | Measured signal | Possible outputs | Conditions and limitations |
|---|---|---|---|
| Spectroscopic ellipsometry | Change in polarization after reflection | Model-dependent film thickness and optical constants for a defined stack | Requires a suitable optical model, known layer order and adequate parameter sensitivity; no universal range or accuracy applies |
| Spectral reflectometry / interference | Wavelength-dependent reflected or transmitted intensity | Model-dependent thickness, reflectance/transmittance and selected optical properties | Requires resolvable optical contrast and an appropriate film-stack model; roughness, absorption and multilayers affect the result |
| X-ray fluorescence (XRF) | Element-specific fluorescent X-ray intensity | Calibrated thickness and elemental information for suitable films | Requires material-specific calibration and adequate elemental sensitivity; this guide does not assign XRF to a current TDM product |
| Step-height profilometry | Vertical height difference across a prepared film step | Step height used as a thickness reference under defined geometry | Requires a measurable step; contact stylus methods can interact with soft or delicate surfaces |
| Cross-sectional SEM / TEM | Direct image of a prepared film cross-section | Local structural and thickness information at the imaged position | Requires sample preparation and is local and destructive or invasive; generally used for reference or failure analysis |
Published TDM Thickness and Metrology Ranges
These rows reproduce model-specific public claims. A blank or unpublished value is not filled by borrowing a range from another product.
| Model | Configuration | Published measurement | Published specifications |
|---|---|---|---|
| SE100 | Offline | Thickness, reflectance, transmittance, n, k, band gap and PL; point sampling | 5–1200 nm; repeatability ≤ ±1%; 10 × 10 to 220 × 220 mm samples; calculation < 10 s |
| SE200 | Offline | Micro-area film thickness, n/k, reflectance spectrum and mapping atlas | 4 nm–450 µm; 1–100 µm spot; repeatability ≤ 0.02 nm; absolute accuracy 0.2% or 1 nm; 4–12 inch wafers |
| SE8000 | Offline | Imaging 3D thickness, multi-layer film metrology and uniformity visualization | Full-range continuous spectrum collection and automatic measurement at preset positions; numerical range not published |
| SE600X | Inline | Thickness, absorption, reflectance, transmittance and PL (band gap, peak intensity, peak position and FWHM) | 5–1200 nm; 10 Hz sampling; 31 measurement points; no sample preparation |
| SE31 | In-situ | Wet-film thickness and reflectance from a slot-die coating head | SDK, Ethernet/power connection and machine start/stop triggers; numerical range not published |
| SE310 | In-situ | Continuous single-spot wet-film thickness and reflectance | 300 nm–20 µm; repeatability < 1%; 15 Hz; 1.5–2 mm spot; working distance < 5 mm |
| SE31-FM | In-situ | Transmission/reflection dual-mode optical-film thickness monitoring | 350–2400 nm; wavelength resolution < 0.2 nm; film-thickness accuracy ±0.1% on standard optical-film systems; PLC integration |
Select a Configuration by Measurement Stage
Offline Laboratory Measurement
SE100 publishes 5–1200 nm point measurement with selected optical and PL outputs. SE200 publishes 4 nm–450 µm micro-area measurement. SE8000 publishes imaging 3D and multi-layer functions without a numerical range.
Inline Perovskite Measurement
SE600X publishes 5–1200 nm thickness plus absorption, reflectance, transmittance and PL at 10 Hz with 31 measurement points.
In-Situ Coating Monitoring
SE31/SE310 address slot-die wet-film thickness and reflectance; SE31-FM is a separate wide-band T/R optical-film route. Compare their ranges and interfaces independently.
Application Context Changes the Specification
Semiconductor and Wafer Films
Define the complete layer stack, expected thickness window, wafer size, spot size and whether n/k, reflectance or mapping is required. SE200 publishes 4–12 inch wafer compatibility and micro-area measurement.
Photovoltaic and Perovskite Films
Specify whether the task is laboratory point measurement, inline full-stack measurement, PL correlation or active wet-film monitoring. SE100, SE600X and the In-situ models cover different stages.
Display, Sheet and Optical Films
Provide sample dimensions, optical transmission/reflectance requirements and mapping or uniformity needs. Do not infer large-area coverage from a model whose public sample size is smaller.
Coating-Process Monitoring
Separate slot-die wet-film monitoring from wide-band optical-film monitoring. SE31/SE310 and SE31-FM use different measurement routes and publish different specifications.
Information Needed Before Selecting Equipment
- Layer order, materials, substrate and expected thickness range.
- Transparent, absorbing, metallic, rough or patterned film condition.
- Sample dimensions, curvature, spot size and mapping positions.
- Required outputs: thickness only, n/k, T/R, PL or uniformity.
- Offline, inline or active-process measurement stage.
- Accuracy, repeatability, cycle time, environment and interfaces.
- Reference sample, calibration method and repeat count.
For product-backed ranges and a direct comparison, see Film Thickness Measurement Equipment by Model and Range and Thin Film Metrology Systems and Model Comparison. For method selection — spectral reflectance, ellipsometry, profilometry and optical profiling — see How to Measure Thin Film Thickness.
Request a measurement configuration
Thin Film Thickness: Quick Answers
How thin is a thin film?
There is no single universal thickness cutoff. “Thin” is application-dependent and means the layer is sufficiently small for interfaces, optical interference, transport or surface effects to matter. For equipment selection, use the actual expected range rather than a generic definition.
What units are used for thin film thickness?
Nanometers and micrometers are common. One micrometer equals 1,000 nanometers; one ångström equals 0.1 nanometer. Record the unit explicitly in every specification and data export.
What is the most accurate thin film thickness method?
No method is universally most accurate. Suitability depends on material, transparency, roughness, number of layers, available optical constants, required spot size and whether a prepared step or cross-section is acceptable. Accuracy must be stated for a defined sample, model and test condition.
Can thin film thickness be measured without damaging the sample?
Yes, selected optical methods are non-contact and non-destructive when the film stack produces a usable signal and model. Profilometry may require a step and contact; cross-sectional electron microscopy requires sample preparation.
What thickness ranges do current TDM products publish?
Published ranges are model-specific: SE100 and SE600X list 5–1200 nm; SE200 lists 4 nm–450 µm; and SE310 lists 300 nm–20 µm for slot-die wet films. SE31 and SE8000 do not publish a numerical thickness range, while SE31-FM publishes spectral and accuracy conditions rather than a universal thickness range.
