Silicon Nanowire Hybrid Metrology For the 7nm Node

Outline

• Motivation

• Introduction to the InSight 3DAFM

• PeakForce Tapping Mode

• Technological Advances for Design Based Metrology

• Case Study: Hybrid Metrology for Gate All Around Silicon Nanowires (GAASiNW)

• Conclusion

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Motivation for a Hybrid Metrology Approach to the Characterization of SiNW

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3DAFM for Depth and CD Metrology

• Production-based Depth Metrology

• High throughput allows 100% lot sampling

• Compatible with 22nm and 14nm node

• Extendible to the 10nn node

• Unique 3D characterization for process development

• Line edge roughness, line width roughness

• FinFET development

• Sidewall angle, profile

• TEM replacement for profile measurements

• Fast turn-around time & economic

• Non-destructive, no sample preparation

• Sub-nm reference metrology

• Best-in-class measurement uncertainty for CD, depth and sidewall angle

• Scatterometry model development and verification

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3DAFM for Depth, Roughness and CD Metrology

TappingMode

CDMode DTMode

PeakForce Tapping

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PeakForce Tapping:Direct force control, wide control range, and high resolution

Feedback Controlled Interaction Force

T

Peak Force Control Range

pN ~ N

• Sinusoidal ramping at sub-resonance frequencies• Retains accurate Z positioning, even at ramp rates ~2kHz• Avoids resonances of cantilever to avoid filtering effect

• Real feedback loop force control• Force control benefits from the results of prior force curves

• Best force control, highest resolution, and greatest stabilityBruker Webinar

What is Hybrid Metrology?

• Hybrid Metrology is the concept that to meet the metrology requirements of cutting edge semiconductor manufacturing, data from multiple metrology sources must be combined or “hybridized”

A

BC

Hybrid

Metrology

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tool 1,2 tool 3,4,5

P

True CD

TMU

CD

tool 1,2 tool 3,4,5

Pro

babi

lity

MeasurandTrue Value

TMU

CDMeasurement Value

Hybrid Metrology

Statistical Hybrid Metrology – OCD Calibration

Feature Hybrid Metrology – TEM and CDAFM

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Technology Advances for Design Based Metrology (DBM)

• Multi Point Registration

• AFM Global Alignment

• XML Based Recipe Generation

• CAD Based SPM Zoom

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Multipoint Registration – Dynamically Eliminate Orthogonality and Scale Errors

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(X1, Y1)D(X2, Y2)D(X3, Y3)D(X4, Y4)D

(X1, Y1)W(X2, Y2)W(X3, Y3)W(X4, Y4)W

Multi Point Alignment

⋯⋮ ⋱ ⋮

⋯Transformation

MatrixDesign Coordinates Printed Wafer Coordinates

Introducing AFM Global RegistrationBringing AFM Resolution to Alignment

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Optical AlignmentAFM AlignmentLoad Wafer

Go To First Site

Optical Alignment 1

AFM Alignment 1

Optical Alignment 2

AFM Alignment 2

AFM Alignment N

Design Based Metrology (DBM) for the InSight 3DAFM

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<XMLRecipe> Depth <\XMLRecipe><Mode>PeakForce Tapping<\Mode><ImageSize> 10 µm <\ImageSize>< Probe> ScanAsystAir<\Probe>

XML Recipe File

CAD Clips

Measurement ResultsReport<CD1>1.556<\CD1><CD2>2.734<\CD2><CD3>0.668<\CD3>

CAD Clips for SPM Zoom

• CAD (GDSII, OASIS, TIFF) clips are used to perform the SPM Zoom pattern recognition

• Enabled true offline recipe development• No need for sample wafer to teach SPM Zoom models

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SEM AFM Hybrid Metrology Flow Chart

SEM

1. Recipes are defined on design layout2. Same input data is used for recipe generation to the two tools3. Measurements are performed on the same sites4. Model calibration is enabled based on other tool measurements

DBM utility

Images

“Recipe” file

Results

“Wafer Map” file

Output to FAB:

• Height measurements (SEM/AFM)

• CD (SEM/AFM)

Data processing

Results

AFM

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Wafer Map and Coordinate System

Design Based Recipe AFM measurement

AFMSEM

Recipe for the two tool is generated from CAD layout

Flow validation was performed on unique pattern

CDSEM measurement

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Acknowledgements

• The work presented as the case study here was done in collaboration with IBM and Applied Materials

• Portions of this work were presented at SPIE Adv. Lithography 2014

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SiNW Buckling

• Measurement results show that thin SiNW buckles

• Buckling can impact device performance

• Metrology challenges

Measure ~4-10 nm SiNW with 0-10 nm buckling

Measure buckling on the Z-axis, height

Source

Drain

8 nm SiNW 200nm pitch

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SEM 3D Measurement Results

• SEM Measurement results show:

Symmetrical spread of buckling on the X-axis

Most wires sag on the Z-axis buckling is mainly towards the wafer

Question – Is this buckling real or induced by the measurement?

Height(Pixels)

X(Pixels)

SiNW # 1 SiNW # 2 SiNW # 3 SiNW # 4 SiNW # 5 SiNW # 6

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SiNW AFM Settings and Measurements

• Image Acquisition Mode: Peak Force Tapping• Probe: High Aspect Ratio ScanAsyst Air

ScanAsyst Air

Buckling is visible and measurable with AFM

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CDSEM vs AFM Measurements

CDSEM Measurement

AFM measurement

Measurements of the same SiNW targets show the same buckling

behavior

SiNW buckling is not a SEM or AFM scanning artifact

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Overlapping AFM and SEM Images

CD measurements comply between tools

SiNW buckling orientation is similar

Target VTSCAT2_4_5_fx1_fy-1

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AFM results indicate:

Symmetrical spread of buckling on the X-axis

Most wires sag on the Z-axis

Same behavior is measured on fresh sites (not measured with SEM)

AFM 3D SiNW Characterization

AFM top view

3D Tilt View AFM Image

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AFM vs SEM Height Measurements

On both tools:

SiNW height variation demonstrate similar trend

SiNW 3 sag less, SiNW 2 sag most

CDSEM model can be calibrated based on the AFM measurements

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CDSEM vs. AFM Height Measurements

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CDSEM to AFM - CDSEM Model Calibration

Calibration results indicate:

Height measurements and trend variation shows general correlation

Correlation includes residual noise of SEM and AFM, further research is ongoing

CDSEM pixel size in Z-axis can be calibrated according to AFM

Wire ID Slope [nm] Offset [nm] TMU [nm]SiNW 2 0.735 2.580 1.332SiNW 3 1.013 -5.440 0.354SiNW 4 1.071 0.790 0.809SiNW 5 1.389 -2.820 3.912SiNW 6 1.123 0.600 2.091

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Conclusion

• Advanced node devices require Hybrid Metrology

• In order to meet the Hybrid Metrology needs, metrology systems must be Design Based Metrology capable

• The InSight 3DAFM is DBM capable enabled through recent advances• Multipoint AFM Registration• XML and CAD Based Recipe Generation

• In the case study presented, design data and results are shared between a CD-SEM and the 3DAFM to generate a complete data set for 7nm node Gate All Around Silicon Nanowire devices.

• Sean Hand: sean.hand@bruker-nano.comBruker Webinar

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