Scatterfield Zero Order ImagingScatterfield Zero Order Imaging

Dr. R. M. Silver, Dr. R. Attota, and Dr.R. Larrabee

Extending optical measurement limits well beyond conventional expectations using engineered illumination.

• Optical microscopy– magnification, image forming optics,

engineered illumination fields

• Optical scatterometry– superb sensitivity, statistical averaging,

single angle of illumination

A new method which combines the best attributes of:

Scatterfield optical imaging: Measuring 10 nm or 20 nm sized features with 450 nm wavelength light. Well beyond conventional resolution limits using engineered illumination and structured targets.

• Primary Semiconductor Applications– Critical Dimension (CD) metrology– Overlay metrology– Defect inspection

• Nanomanufacturing Applications– Fuel cell process control– Arrayed nanoparticles– Nanometer sensitivity

• A technique which enables scatterometry type measurements on very small targets– High throughput, low cost– In chip semiconductor applications– Reduced scribe line target size– Parallel measurements of multiple targets

Scatterfield Microscopy

Scatterfield optical imaging enables the microscope to be characterized in fundamental ways previously inaccessible allowing substantially improved theoretical understanding of optical microscope imaging.

• Angle resolved characterization is fundamental to accurate microscopy

– Optical system alignment – Polarization characterization– Angular transmissivity – Source characterization

• Nanometer scale measurements can be achieved using angle resolved scatterfield microscopy.

– Quantitative modeling demonstrated– Nanometer consistency with reference metrology– Dense zero order arrays can be measured– No immediate limitation of feature size or density

Scatterfield Microscopy

Tool Configuration: Illuminator LayoutTool Configuration: Illuminator Layout

• 1 cm diameter conjugate back plane for illumination engineering.

• Fourier plane engineering on illumination and collection paths.

• Can define x and y polarization.• y (parallel) and x (perpendicular) scan axes relative to target

lines.

LED

aperturerelay lens objective

xsample

sampley

xsample

sampley

Scan axis configuration

Condenser

Back focal planeof condenser lens

Field L

ens

ABC

A

B

C

Even illuminationat the object focal plane

Field Diaphragm

Sensitivity: 100 nm CD, Pitch 300 nmSensitivity: 100 nm CD, Pitch 300 nm

(0,0) Die:Top = 118.6 nmMid = 114.7 nmBottom = 128.8 nm

(0,-1) Die:Top = 116.1 nmMid = 112.3 nmBottom = 125.1 nm

(-1,-1) Die:Top = 102.1 nmMid = 117.0 nmBottom = 128.9 nm

Best Fit for 100 nm CD, Pitch 600 nmBest Fit for 100 nm CD, Pitch 600 nm

• Quantitative agreement obtained for optical modeled measurements.• Optical/AFM agreement on the nanometer scale achieved for the first time.

Optical Modeling: Theory to Experiment Agreement

Plots show intensity as a function of angle. Experimental sensitivity on the left and theory to experiment comparison on the right. These data are an example of zero order imaging with sub-resolution features.

Overlay/CD Targets: Parallel Measurement CapabilitiesOverlay/CD Targets: Parallel Measurement Capabilities

Line/trench structures90nm 1:3

-40 -30 -20 -10 0 10 20 30 400

0.2

0.4

0.6

0.8

1

1.2

Linearity - p-polarization

Incident Angle (degrees)

Inte

nsity (

Rela

tive t

o B

ackgro

und) A

B

C

Linearity ArrayZero order 50 nm CDs

• The lines are approximately 60 nm CD +/- 5 nm.• 5 nm changes in linewidth show significant response.• Meets important needs of combined CD and overlay

metrology.• In chip metrology capabilities.

Summary: Low cost high, throughput technique with applications in process control and metrology for semiconductor manufacturing and emerging nanotechnology industries. Can measure sub-20 nm sized features, densely positioned with nanometer scale accuracy over very large areas.

Patent Application, serial # 11/866,589 filed 11/1/07

Scatterfield Zero Order ImagingScatterfield Zero Order Imaging