Scanning white light interference microscopy

Micro to millimetre range structures can be measured at VTT MIKES using scanning white light interference microscope (SWLI). The SWLI (Bruker ContourGT-K) has sub-nm vertical and μm level horizontal resolution. It can measure square mm areas in a single scan. The main features of the device are listed in the table below. Benefits of SWLI compared to other instruments with similar vertical resolution include large measurement area, ability to measure high steps and overlapping surfaces inside of transparent structures. Examples of objects suitable for measurement with SWLI: bearings, contact surfaces, topography and wear of surfaces, semiconductors and MEMS, medical instruments and implants, optical components, precision-machined components.  

We do different measurements using the SWLI

  • measurement service for different type of objects
    • surface shape measurements
    • x,y,z dimensions of details on surface
    • film thickness measurement, layer separation
    • surface roughness (2D and 3D ISO roughness parameters), flatness, deviation from a shape
  • calibration of different instruments
  • calibration of reference artefacts
    • step heights, air gap artefacts, film thickness
    • artefacts
    • calibration of reference artefacts
    • step heights, air gap artefacts, film thickness artefacts

Real measurement uncertainty is case specific and it depends on the measurement environment, properties of the instrument and of the measured sample. At VTT MIKES we take care that the sample is clean, sample temperature is known, sample is well attached and properly aligned. Measurements results are traceable to the SI metre via our own transfer standards such as step height standards and laser interferometer.Measurements are done under consistent conditions and results are well documented.

  
Properties of the SWLI at VTT MIKES. 

 Property Data
Optical x-y resolution3.8 – 0.7 µm
Pixel size7.2 – 0.2 µm
Vertical resolution< 0.1 nm
Step height measurement:
    – repeatability
    – accuracy
 
< 0.1 %
< 0.75 % 
Sample reflectivity0.05 % – 100 %
Maximum surface tilt smooth samples3° (2.5× objective), 18.9° (20× objective)
Objectives2.5× ja 20× objectives, 0.55×, 1× ja 2× zoom lenses
Measurement area:
    – smallest magnification
    – largest magnification
(X × Y × Z mm3):
3.5 × 4.6 × 3.5
0.4 × 0.6 × 3.5
Measurement area in pixels640 × 480
SoftwareVision64 Analysis Software, MountainsMap, MatLab
Maximum size of measured obejct10 cm high × 20 cm wide, one dimension can be much longer
Ability to measure overlapping surfaces 2 surfaces in single measurement
Maximum depth is dependent on refractive index, geometry and magnification, e.g. it is possible to measure through 0.3 mm thick glass
7 mm maximum depth limited by working distance

 

Contact

  • Ville Heikkinen, Research Scientist, tel. +358 50 415 5980, email Ville.Heikkinen(at)vtt.fi    

  

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