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SureshK.RamasamyPhDMarch 2013
COHERENCESCANNINGINTERFEROMETRY
Part1.Basics,CalibrationandAdjustment
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Noncontact areal surface measurement systems Coherence scanning
interferometer Standards ISO, ASME Part standards Vibration test
Calibration, adjustment procedures Objective focus optimization
Email id: [email protected]
OUTLINE
Sciencestartswheremeasurementstarts D.I.Mendeleev
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QUESTIONS?
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Potential3DMeasurementInstruments
Contacting StylusChromatic Length Aberration Confocal
MicroscopySEM StereoscopyScanning Tunneling MicroscopyAtomic Force
MicroscopyOptical Difference Profiling Angle Resolved SEM
Areal TopographySenses Z(X,Y) or
Z(X) as a function of Y
TriangulationFastMoirInterferometerConfocalMicroscopePhaseShiftingInterferometerVerticalScanning(WhiteLight)Interferometer
Promise Speed & accuracy Laboratory
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Triangulation
1 . F a n g J u n g S h i o u , M i n X i n L i u , D e v e l o
pm e n t o f a n o v e l s c a t t e r e dt r i a n g u l a t i o n
l a s e r p r o b e w i t h s i x l i n e a r c h a r g e c o u p l
e d d e v i c e s ,O p t i c s a n d L a s e r s i n E n g i n e e
r i n g , 4 7 ( 2 0 0 9 ) 7 1 8
2 . S t a g e o n e : L i g h t R e f l e c t i o n Mo d e l s f
r om we b s i t eh t t p : / /www . g r a p h i c s . c o r n e l l
. e d u / r e s e a r c h / g l o b i l l um / r e f l mo d e l . h
tm l ,a s o f 0 5 / 0 5 / 2 0 1 0
Working principle of a triangulation probe based on Scheimpflugs
principle
Bi-directional reflectance distribution model
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MoirInterferometer
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ChromaticLengthAberration
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Top
Bottom
ConfocalMicroscopy
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-20 -10 0 10 20z axis (micrometers)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Focu
s fu
nctio
n Intensity
Fig 3b20X
Gradient
LED Light source480 nm
PBS Microdisplay
CCD
Objective
ConfocalMicroscopy
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Waves of Light
Wavelength
Light is comprised of wavelengths of energy
The length determines the color of l ight
White l ight (a combination of different wavelengths) provides a
larger measurement range.
TheoryofLight
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Interference is the phenomenon caused by superposition of two
electromagnetic waves
When these two waves are in phase then the result is a bright
band and if they are out of phase the result would be a dark
band
Mathematical Representation :
is the interference term.
(2 1) is the phase difference between two waves.
Constructive Interference
Destructive Interference
TheoryofInterference
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TheoryofInterference
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SampleSurfacesandtheirpatterns
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WLI.Underthehood
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Differentwaystofindthepeak
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InterferenceFringes
Fromfringesto3Dsurfacemap
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CoherenceScanningInterferometera
b
d
e
f
gh
ijl
n
m
r
q
k
a Light source (halogen / LED)b Dichoric mirrorc Laser source
(optional)d Opticse Aperture stopf Field stopg 45 Mirrorh Beam
splitteri Interferometric objectivej Reference mirrork Measured
surfacel Scanner (PZT / Stepper motor)m Zoom / magnification tube
setupn Beam splittero Polarizer (Optional)p Detector 2 (Optional)q
Polarizerr Detector 1 (CCD / CMOS)
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CoherenceScanningInterferometera
b
d
e
f
gh
ijl
n
m
r
q
k
a Light source (halogen / LED)b Dichoric mirrorc Laser source
(optional)d Opticse Aperture stopf Field stopg 45 Mirrorh Beam
splitteri Interferometric objectivej Reference mirrork Measured
surfacel Scanner (PZT / Stepper motor)m Zoom / magnification tube
setupn Beam splittero Polarizer (Optional)p Detector 2 (Optional)q
Polarizerr Detector 1 (CCD / CMOS)
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CoherenceScanningInterferometera
b
d
e
f
gh
ijl
n
m
r
q
k
a Light source (halogen / LED)b Dichoric mirrorc Laser source
(optional)d Opticse Aperture stopf Field stopg 45 Mirrorh Beam
splitteri Interferometric objectivej Reference mirrork Measured
surfacel Scanner (PZT / Stepper motor)m Zoom / magnification tube
setupn Beam splittero Polarizer (Optional)p Detector 2 (Optional)q
Polarizerr Detector 1 (CCD / CMOS)
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CoherenceScanningInterferometera
b
d
e
f
gh
ijl
n
m
r
q
k
a Light source (halogen / LED)b Dichoric mirrorc Laser source
(optional)d Opticse Aperture stopf Field stopg 45 Mirrorh Beam
splitteri Interferometric objectivej Reference mirrork Measured
surfacel Scanner (PZT / Stepper motor)m Zoom / magnification tube
setupn Beam splittero Polarizer (Optional)p Detector 2 (Optional)q
Polarizerr Detector 1 (CCD / CMOS)
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CoherenceScanningInterferometera
b
d
e
f
gh
ijl
n
m
r
q
k
a Light source (halogen / LED)b Dichoric mirrorc Laser source
(optional)d Opticse Aperture stopf Field stopg 45 Mirrorh Beam
splitteri Interferometric objectivej Reference mirrork Measured
surfacel Scanner (PZT / Stepper motor)m Zoom / magnification tube
setupn Beam splittero Polarizer (Optional)p Detector 2 (Optional)q
Polarizerr Detector 1 (CCD / CMOS)
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CoherenceScanningInterferometera
b
d
e
f
gh
ijl
n
m
r
q
k
a Light source (halogen / LED)b Dichoric mirrorc Laser source
(optional)d Opticse Aperture stopf Field stopg 45 Mirrorh Beam
splitteri Interferometric objectivej Reference mirrork Measured
surfacel Scanner (PZT / Stepper motor)m Zoom / magnification tube
setupn Beam splittero Polarizer (Optional)p Detector 2 (Optional)q
Polarizerr Detector 1 (CCD / CMOS)
c
p o
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NT8000 (Veeco) CCI (Taylor Hobson) NV6300 (Zygo)
ExamplesofCSIsystems
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Configurations
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ISOStandards ISO / TC 213 / WG16 25178
NominalCharacteristics 602 Confocalchromaticprobe 603
Phaseshifting interferometric microscopy 604 Coherencescanning
interferometric microscopy 605 Pointautofocusprobe 606
Focusvariation 607 ImagingconfocalmicroscopyCalibration 702
Confocalchromaticprobe 703 Interferometric microscopy
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NPLGPGs Good Practice Guide No. 108: Guide to the Measurement
of
Smooth Surface Topography using Coherence Scanning
Interferometry
Good Practice Guide No. 116: Guide to the Measurement of Rough
Surface Topography using Coherence Scanning Interferometry
Giusca CL, Leach RK, Calibration of the metrological
characteristics of areal surface topography measuring instruments,
Proceedings of the 2nd International Conference on Surface
Metrology 2010, WPI, USA pp. 145153.
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ReferenceFlatStandard Silicon Carbide Surface SubAngstrom level
flatness Used to establish bestcase measurement capability
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StepHeightStandard Chromium coated on etched Quartz surface NIST
Traceable Calibration and adjustment of Z axis measurements
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LateralCalibrationStandard Platinum coating on etched Silicon
dioxide surface NIST Traceable Setting magnification and TRC
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OpticalDimensionalStandard Chrome on glass photomask NPL
Traceable
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SurfaceRoughnessSpecimens ISO 5436 1:2000
TypeC(Spacingmeasurementstandards)
TypeD(Roughnessmeasurementstandards)
NIST Traceable ITF and Algorithm depenedencies
a
b
c
Cross sectional profiles of (a) random surface (b) sinusoidal
surface and (c) square wave surface.
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Siemens Star
Weckenmannetal,Practiceorientedevaluationoflateralresolutionformicro
andnanometermeasurementtechniques,MeasurementScienceandTechnology,20(2009)065103(8pp)
ITF and Algorithm dependencies
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Vibrations
(a) Measurements taken under ideal environment (b) under high
vibration levels, seen as ripples of missing data.
a b
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Vibrations
y = 0.6255x + 2.3434R2 = 0.9951
0
50
100
150
200
250
300
0 100 200 300 400 500
Peak to peak noise level (nm)
Mea
suremen
t error
(1 S
igma in nm)
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Calibration
Z axis Systemswithreferencesignal
Systemswithoutreferencesignal
Stepheightartifactbasedusercalibration XY axis
Presetmagnification Usertunablemagnification
Lateralcalibrationstandardbasedusercalibration
Specificforeachobjectiveandzoomtubesetting Linear
doesntincludewarpingerrors
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ZaxisCalibration
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LateralCalibration
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LateralCalibration steps
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TRCSetup
Image of one corner of Lateral calibration standard used for
finding offset between different magnifications
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ReferenceMirrorFlatnessError
Reference mirror surface error map for a chosen magnification
(objective and zoom tube combination)
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ObjectiveFocusOptimization
Effect of focus on roughness for selected samples with varying
roughness values
0
20
40
60
80
100
120
140
Part 1 Part 2 Part 3 Part 4 Part 5 Part 6
Low (< 40 nm) Medium (41 - 80 nm) High (81 - 120 nm)
Pa (n
m)
After 50x Focus Pa (nm) After Defocus Pa (nm) After Refocus Pa
(nm)