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Thickness

Multi-layer and single-layer films

Low-coherence profilometers deliver fast and reliable non-contact thickness measurements of single-layer and multi-layer films – with precision better than 1 µm.

2D optical cross-section (B-Scan) of photoresist coating on a 6” diameter semiconductor wafer

2D cross-section (B-Scan) of an unevenly applied thick film of photoresist coating on a 6” diameter semiconductor wafer

  • Films and film stacks: 10 µm to several mm thick
  • High-speed scanning: 1,000 to 30,000 points/sec and higher
  • Real time thickness measurements: for substrates and for entire film stack
  • Easy visual inspection: high-resolution depth profiles, 2D cross-sections (B-scans or C-scans) and 3D volumetric images

Materials may be reflective or nonreflective, smooth or rough, stationary or moving. See more on what we can measure.

Intra-ocular lens: 2D cross-section extracted from acquired 3D image

Intra-ocular lens: 2D cross-section extracted from acquired 3D image

Surface or sub-surface roughness, shape or topography may be acquired at the same time as thickness. See How low-coherence interferometry works.

Advantages of inspecting with fiber-based probes

Because Novacam profilometersscan surfaces with fiber-based optical probes, they offer significant advantages.

  • They acquire long profiles: probes acquire surface data one point at a time, at high speeds of 1 to 30 kHz and higher. No need for time-consuming surface tiling.
  • They offer configuration versatility for benchtop or in-process inspection. Probes are mounted onto a benchtop or inline motion mechanism suitable for each application: X-Y table, galvo-scanner, rotational scanner, robotic arm, etc.
  • Probes can work far from profilometer enclosure, as far as 1 km away, without signal degradation.
  • Small probes reach inside to inspect interiors of small-diameter tubes, bores, etc. See inspection in hard-to-reach spaces.
  • Rugged probes perform even in extreme temperatures or in radiation. See inspection in hostile environments.

Novacam standard and small-diameter fiber-based optical probes

Novacam fiber-based optical probes

Example of multi-layer thickness measurement

High-grade polymer tubing, such as medical catheter tubing, must be closely monitored during extrusion so that dimensions continuously adhere to tight specifications. With the low-coherence profilometer probe positioned right at the extruder exit (diagram on the right), the tubing cross-section is actuired continuously and an efficient production control loop is established:

  • The probe acquires the thickness of the advancing thin tube as a long profile – at up to 30,000 points (A-scans) per second.
  • Each A-scan delivers optical thickness of the upper wall, the enclosed air space, and the lower wall.
  • Application software transforms optical data into physical dimensions of the tubing (table on the right).
  • The index of refraction, IR, can be calculated if needed.
  • Cross-section dimensional data is streamed to process-control software which adjusts extruder parameters in real time.

Continuous inspection cuts down on extruder down-time, reduces material waste, and lowers overall production costs.

Dimensional profiling of a thin tube (medical catheter, < 1.5 mm diameter) during extrusion

1-probe setup: dimensional profiling of a thin tube (medical catheter, < 1.5 mm diameter) during extrusion

 
Tube dimensions and IRValue
thickness of upper wall0.131 mm
thickness of lower wall0.162 mm
inner diameter0.852 mm
outer diameter1.145 mm
calculated index of refractionIR = 1.512
Single point data for medical catheter tube

Probe multiplexing for additional ROI

Several fiber-based probes can be multiplexed to a single detector for simultaneous thickness measurements on different aspects of a production line.

For example, the tube inspection setup above can be extended by adding a second probe at the extruder exit (diagram on the right). In this way, the operator is able to monitor tube dimensions along two axes continuously, achieving even greater quality control with minimal extra investment.

probe setup for dimensional thin tube profiling along two axes

2-probe setup: simultaneous dimensional thin tube profiling along two axes

Thickness measurement applications

Low-coherence profilometers acquire thicknesses in a range of domains:

  • Opthalmology: inspection of regular or intraocular contact lenses
  • Semi-conductors: coating on MEMS devices, semiconductors, hybrid circuits, fuel and solar cells
  • Aviation and automotive: protective films
  • Optical: etching and deposition thickness on waveguides
  • Electronics: thick film photoresist coating on electronic wafers
  • Bio-medical: coatings which protect devices from corrosion or patients from complications
  • Others: conformal coating, protective tool coating, vacuum coating