1

Improvements in automation for shell surfaces holographic

characterizations C. Hermerel, C. Chicanne, L.Jeannot, A. Choux, E. Busvelle(1), J-B. Vioix(1), P. Mérillot, G. Pascal

CEA Valduc, F-21120 Is-Sur-Tille. (1) Université de Bourgogne, F-89000 Auxerre.

21/05/2012

TFM 21/05/2012 2

Summary

• DHM principle

• Data processing software Principle : Reconstruction of the sphere – 3D visualization Bumps, divots characterization Others defects

• Metrology capability

• Conclusion / Perspectives

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Introduction – DHM principle

Unorthogonal axis

Microshell

Camera

Lens

Mirror

Objective

R

O

O

R

Laser Source Object beam Reference beam

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Hologram (250 x 250 µm²) intensity

fringes

Phase unwrapped Phase without spherical component

Introduction – DHM principle

Microshell

DHM

100 µm

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Reconstruction of one strip

Recognition of interest points on neighboring strips

3D Reconstruction of the sphere

Search of a translation between two images (rotation along a meridian) using image correlation.

3D sphere visualization

Estimation of the covered surface rate

Bumps, divots characterization

- Morphological analysis of the image is used to localize the defects, - They are measured using a regression with a spherical cap.

Data processing software : principle

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Bumps, divots characterization – software evolution

Data processing software : improvements

Numerical grayscale gap between two images (due to image corrections)

With the previous software version some ghost bumps were regularly detected due to unavoidable numerical gap between grey levels on two neighboring images : Example :

0

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9000

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12000

0 10 20 30 40 50 60 70 80 90 100Largeur à mi-hauteur (µm)

Haut

eur (

nm)

Aucun défaut au-delà Modèle<20 défauts au delà Modèle<100 défauts au delà ModèleBumps bumps abhérants

Ghost bumps

Hei

ght (

nm)

FWHM (µm)

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0

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0 50 100 150

Largeur à Mi-hauteur (µm)

Hau

teur

(nm

) The ghost bumps are automatically suppressed using a correlation coefficient (< 0.1). The bumps are directly represented in Haan curves (rev.3) with a color code (function of the correlation coefficient) - to ensure that the points are not ghost data - to have a warning on critical big bumps

Bumps, divots characterization – software evolution

Data processing software : improvements

Coefficient >0.9 Coefficient value between 0.7 and 0.9 Coefficient value between 0.4 and 0.7 Coefficient value between 0.1 and 0.4

FWHM (µm)

Hei

ght

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Data processing software : improvements

To check the bumps repartition and to target easily suspicious bumps or defects, the bumps and divots are pointed by a square on the strips with a color code (function of the position on the Haan Curves (rev.3))

Bump between green and “pink”curves (green squares)

Bump under green curve (black squares)

Divot (red squares)

Bump present on another strip (yellow squares) Bump height <120 nm (no square)

Bumps, divots characterization – software evolution

Others square colors Bump between “pink” and blue curves (“pink” square) Bump above blue curve (blue square)

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Data processing software : improvements

For each bump or divot the value of Mixed Mass and PVRMS is now calculated (rev.5)

mixed mass < 10 ng ∑=

n

iim

1

< 5 µm

-1250,00

-1000,00

-750,00

-500,00

-250,00

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0 20 40Largeur à mi-hauteur (mm)

Haut

eur (

nm)

Mix Mass 20

Mixed Mass 0

∑=

n

iim

1∑=

n

iim

1

Rev 3 Rev 5

∑=

n

iim

1

∑=

n

iiPVRMS

1

Hei

ght (

nm)

Hei

ght (

nm)

FWHM (µm)

FWHM (µm)

Bumps, divots characterization – software evolution

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Data processing software : improvements in progress Others defects : scratches and divots Others defects can’t be fitted using classical functions They will be identified with their 2D morphological parameters

R r

S convex envelope perimeter per(conv(S))

Stretching : Rr

=α and concavity : )()((

SperSconvper

=γ

S

0

0,1

0,2

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0,9

1

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9Allongement (α )

Con

cavi

té (γ)

Concavity increase

curvilinear scratch

divots (α and γ near to 1), rectilinear scratch(α near to 0 et γ near to 1) curvilinear scratch(α near to 1 et γ near to 0)

per(S)

rectilinear scratch

Points are plotted with a color code to indicate the maximum depth of each scratch. For example : 0-50 nm : blue 50-100 nm : green …

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• Measure on step height standard calibrated (174 nm measured for 176,5 ± 1,9 nm)

Metrology capability

• Measure on roughness standard calibrated (82,2 nm measured for 79,7 ± 2,5 nm)

Step and roughness : bumps size representative

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AFM / DHM measurements comparison on one isolated bump

DHM : h=887 nm ± 20 nm AFM : h = 902 nm ± 5 nm

The heights measured are similar.

Metrology capability

AFM on spheremapper was used to ensure the capability on DHM on 1 µm high bump.

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New mechanical configuration A new mechanical configuration permits to acquire data along two hemispheres in suppressing shell manipulation between strips acquisition.

The software has been adapted to this new hardware configuration to stitch the two hemispheres data

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Conclusions/Perspectives

The DHM permits fast speed 3D surface image acquisition in order to characterize and count defects (bumps, divots,…) on microshells outer surface.

Conclusions

The DHM metrology capability has been demonstrated with standard calibrated samples and with a comparison with AFM.

Perspectives

The reduction of images number to cover the microshell outer surface is in study (spiral shape travel acquisition) The software will be adapted to this new hardware configuration.

The new DHM mechanical configuration permits to acquire data along two hemispheres in suppressing shell manipulation between strips acquisition.