White White White White LightLightLightLight InterferometryInterferometryInterferometryInterferometry
3D Profilometer
Theory background
• Interferometer uses the superposition principle to combine waves in a
way to extract information from the wave fronts.
• The position of the zero order interference fringe is independent of
wavelength
• A broadband “white light” source is used to illuminate the test and
reference surfaces
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reference surfaces
• The reference beam is reflected by the reference mirror, while the
measurement beam is reflected or scattered from the test surface.
• Reconstruction of the surface based on the fringes snapped by the
camera
Intensity = A + B cos(φ) φ ∽ z 3D topographic image of the
object surface
Light
Plane
Mirau microscope objective
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Convergent lens
Plane reference
mirror
Reference surface
z
Object surface
Interferences
• Step-height and roughness measurement
• White light interferometric profilometer
• Variable field of view due to revolver objectives
• High speed: full image recorded within seconds
Semilab Optical Profilometer
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• High speed: full image recorded within seconds
• Sub-micron lateral resolution
• Sub-nm height resolution
• CCD color camera
• Low sensitivity to vibrations
• Non-destructive
WLICamera resolution: 1024x1024 (2048 x 1088)
Pixel Size (on the sensor): 5.5µmx5.5µm
Acquisition speed: 500 fps (340 fps)
Measurement time (without motion): <1 sec
Depth resolution : < 0.1 nm
Repeatability: σ=0.3 - 6 nm depend on sample
Specification:
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Repeatability: σ=0.3 - 6 nm depend on sample
Multiple heads configuration available
Color Camera option
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Objective (3D) 50x 20x 10x
Maximum FOV (µm) 284x150 568x300 1136x600
Best optical resolution
(Rayleigh definition) (µm)0.5 0.7 0.9
Field of views:
Diamond cut solar cell wafer
1700 nm
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Solar cell wafer inspection of saw mark, surface roughness and features.0
Measurements Positions
Repeatibility measurement
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The Critical dimensions (Top and Bottom) are measured along the yellow axes(nm)
Surface roughness and waviness
Bandpass
(0.027 to
2.75 um)
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Bandpass
(2.75 to
555 um)
Surface roughness and waviness
Bandpass
(0.027 to
2.75 um)
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Bandpass
(2.75 to
555 um)
Surface roughness and waviness
Bandpass
(0.027 to
2.75 um)
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Bandpass
(2.75 to
555 um)
• Semilab is capable to deliver state of art 3d surface profiling metrology using white
light interferometry
• Best resolution available : high resolution camera can deliver data up to 2 Megapixels,
in less than 3s aquisition time
Conclusions
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in less than 3s aquisition time
• Semilab wli technology proved to work for various industrial applications in the flat
panel, solar cell and semiconductor area
• Excellent repeatability is proven to be in the range of few nm-s
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