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OSPrey800OSPrey800

Optical Metrology of OSP CoatingsOSP Film Thickness & Q alit Anal sisOSP Film Thickness & Quality Analysis

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Measurement Technique:Spectral ReflectanceSpectral Reflectance

– Subject sample to various wavelengths of light

– Measure reflected light from the surface of coating and substrate

– Correlate wavelength and reflectance value to ti thi kcoating thickness

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SchematicLight Source

Light Out

SpectrometerFiber Optic Cable

Camera

Reflected Light In

Camera

Focus Motor (Z-axis) E l

Lens Assembly

Enclosure

Transmitted and reflected light

SamplePC

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Solving for Coating Thickness

Iterative process with

• Initial input of– Expected thickness rangep g– Roughness (coating and substrate)– Extinction coefficient (coating and substrate)

Refractive index (OSP chemistry)– Refractive index (OSP chemistry)

• Scan wavelength range, 420nm~665nm

• Measure the reflected light intensity ‘R’ and solve for ‘d’

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Spectral Reflectance Basicsp

2Air/OSP/Copper

nd)2Bcos(ARλπ

+≈Air

Reflected Light, R

1 k1)2cos( ndBAR

λπ

+≈

n1, k1

d ⎠⎞

⎜⎝⎛ −

=B

ARcosn2

d 1-λ

n2, k2d ⎠⎝ Bn2π

f ti i diTransmitted Light

ni = refractive indices,

ki = extinction coefficientsAbsorbed Light

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OSPrey800 Analyzery y

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Control UnitOptical Components mounted on a motorized z-stage

PCB / PWB

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20x Optics20x Optics

Probed Area

PCB / PWB

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Thickness Morphology2-D Map of Sample Surface

Each camera pixel measures a discrete region (1µm x 1µm) on a total surface area of 330 µm x 265µm on the sample.

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Thickness (Å)

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Interference Characterization• A sample spectrum is obtained from each pixel. This

spectrum may or may not produce a valid thicknessspectrum may or may not produce a valid thickness measurement dependent upon the physical properties of the measurement location.

• Individual measurement points may be invalid for one or more of the following reasonsg– Non-uniform OSP thickness distribution– Cu substrate oxidation

Oth ti l t i ti– Other particle contamination– Excessive substrate (Cu) roughness

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Interference by Contaminationy

OSPOxidationDust

Bad point

Good pointCuCu

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Interference by Roughness (r)Problem = “r” value is changingProblem = r value is changing

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Goodness of Fit (GOF) Determination

• Blue points represent measured Spectrum from one pixel

spectrum• Red line represents closest

t hi th ti l tmatching theoretical spectrum• Correlation between the two

spectra is quantified with a GOFspectra is quantified with a GOF value

• GOF = 1 perfect correlation• GOF = 0 no correlation

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GOF DeterminationUser can define a GOF threshold to separate “good” from

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Goodness of FitSystem iterates to find the best spectral fit for thickness.

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X Poor fit GOF=0.011 Good fit GOF=0.995

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2-D Thickness Mapp

GOF value vs. user-defined thresholdGOF badBlack = cannot be measured

accurately

GOF goodThickness is color scaled

Thickness (Å)

Blue = thick

White = thin

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( )

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Real-time on-screen feedbackfeedback

M tMeasurement

H d / S ftHardware / Software Interface

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CCD Image 2-D Thickness Mapct

ance

Ref

lec

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Wavelength [nm]

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Typical Measurements of ypOSP coatings using OSPrey800

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BGA Sample

Interesting Area of very low OSP coverage

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Key Features of OSPrey800y y• Non-destructive • In-situ• Small spotp• 2-D map• Based on FP• Based on FP• Motorized Z• Auto focus• Dynamic Data Exchage

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y g

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OSPrey800 S ifi tiSpecifications

Excitation- Multi-wavelength optical excitation 420-

665 nm accessed via notch filterselection from a filament source

Optics- Illumination and imaging system with

- Memory: 1 GB DRAM- Monitor: 1280 X 1024- Operating System: Window XP- Ports: At least two USB 2.0 ports

Power SupplyIllumination and imaging system with 20x optical magnification- Fibre Optic Light Guide 1/8"

Detector- CCD detector.

Analysis

Power Supply- 100-240 V, AC, 50-60 Hz, 230 Watts -

Maximum. Fuse provided: 4A, 250VWorking Environment

- 50°F (10°C) to 104°F (40°C) and up to 98% RH non condensingAnalysis

- Processing of wavelength dependent reflectance spectra from OSP thin-film coated samples- Programmable recipe editor for initial

- 98% RH, non-condensing Sample Stage

- Fixed in-plane XY sample stage- Motorized z-axis optical autofocus

Dimensionsparameter definition

Computer- Pentium D or Pentium 4 Processor with HT Technology- Clock Speed: >/= 3.0 GHz

- Measurement Stage: 25 W x 30 D x 46.5 H (cm)- Controller Unit: 27.5 W x 20.7 D x 14.5 H (cm).

Weight

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p- Front Side Bus (FSB) Speed: >/= 800MHz- Hard Drive Capacity: >/= 80 GB

Weight- Measurement Stage: 6.6 kg (14.5 lbs)- Controller Unit: 5.7 kg (12.5 lbs)