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:

Application examples

Step-height measurement

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Critical dimension inspection of step-heightlike profile

Flat Panel Transistor

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Critical dimension of flat panel transistor

Diamond cut solar cell wafer

1700 nm

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Solar cell wafer inspection of saw mark, surface roughness and features.0

Metal surface

3000 nm

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Metal surface inspection of screatches, surface roughness and features.

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Critical dimension of MEMS device

400 nm

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0

Optical surface with dust

1000 nm

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0

Recent WLI demo result: spacers height in FPD structures

6000 nm

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Measurements Positions

Repeatibility measurement

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The Critical dimensions (Top and Bottom) are measured along the yellow axes(nm)

3D view of FPD structures

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Application examplesSurface roughness

935575/4

200 nm

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Surface roughness and waviness

200 nm

RMS=4.797 nm

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RMS=36.273 nm

Surface roughness and waviness II.

RMS=4.797 nm

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RMS=36.273 nm

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250 nm

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Surface roughness and waviness

Bandpass

(0.027 to

2.75 um)

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Bandpass

(2.75 to

555 um)

RMS=9.433 nm

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RMS= 27.298 nm

934344/4

250 nm

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Surface roughness and waviness

Bandpass

(0.027 to

2.75 um)

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Bandpass

(2.75 to

555 um)

RMS=7.762

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RMS= 36.554

934344/128

400 nm

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Surface roughness and waviness

Bandpass

(0.027 to

2.75 um)

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Bandpass

(2.75 to

555 um)

RMS=28.122 nm

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RMS= 50.088 nm

• 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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