Why thickness matters
Film thickness governs the optical and electrical behaviour of coatings: anti-reflection performance of display stacks, sheet resistance of ITO layers, barrier properties of protective coats. Monitoring thickness in-line prevents both over-coating cost and under-coating failure.
Spectral reflectometry (white-light interferometric principle)
Light reflected from the top and bottom interfaces of a transparent film interferes; the spectral fringe pattern encodes the optical path difference, from which thickness is retrieved through the film's refractive-index model. Non-contact, fast (<200 ms per point) and accurate to about ±0.1 µm on standards — the principle behind the HX-FT film thickness meter.
When to choose what
- Spectral reflectometry: transparent/semi-transparent single or few-layer films on known substrates; production QC.
- Ellipsometry: ultra-thin (<10 nm) layers, complex multilayer stacks, research metrology.
- Mechanical profiling (stylus/step): opaque films and step-etched samples; destructive but direct.
Implementation tips
- Know your stack: substrate and each layer's n & k data drive the model library.
- Use recipe-based measurement with pass/fail limits for production consistency.
- Verify periodically with a certified thickness standard.
The HX-FT ships with the OPTICAFILMTEST software suite — a multi-layer model library with 1000+ materials, mapping and SPC reporting for production environments.