2D & 3D ADVANCED TRANSMISSION ELECTRON MICROSCOPY … · 2018-08-08 · | 6 TRANSMISSION ELECTRON MICROSCOPES @ LETI USED IN THESE STUDIES FEI Titan Themis 80-200 kV XFEG gun, Monochromator,

Vincent Delaye, Nicolas Bernier, Zineb Saghi, Guillaume Audoit, David Cooper | 3DAM Metrology Workshop | 20/04/2018

2D & 3D ADVANCED TRANSMISSION ELECTRON MICROSCOPY FOR SEMICONDUCTOR CHARACTERIZATION

[email protected]

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• STEM imaging, Electron tomography

• EDX, EELS-STEM for composition & doping

• TEM (N-PED) for strain measurements

* From R. Schäublin, Advanced Transmission Electron Microscopy 13th PFCM & 1st FEMaS, Rosenheim, May 09th - 13th, 2011 3DAM Metrology Workshop | Vincent Delaye | 20/04/2018

3DAM, TEM for FEOL SiGe Stacked Nanowire« TEM WHEEL » *

3DAM WP3 Structural metrology and defect analysis

3DAM WP4 Compositional and electrical characterization

3DAM WP3 Structural metrology and defect analysis

| 33DAM Metrology Workshop | Vincent Delaye | 20/04/2018

• Introduction, multidimensional TEM

• Strain measurements in a TEM

• Principle & performances of N-PED

• Application to 3DAM sample (strain and composition measurements)

• Electron tomography

• Software

• Application to 3DAM sample

• Analytical electron tomography

• Summary

OUTLINE

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• Modern TEM capabilities:

• Fast EELS or EDX acquisition in STEM mode

• Composition measurement, quantification

INTRODUCTION,

ANALYTICAL STEM TECHNIQUES, 2D & 3D

3DAM Metrology Workshop | Vincent Delaye | 20/04/2018

Omega gate transistor (STEM ADF)

HfSiON

TiN

SiO2

Si (poly)

NiPtSi

Electron

Tomography

Electron Tomography:

one image, datacube / tilt angle

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• Modern TEM capabilities:

• Fast NBED pattern acquisition

• Strain measurement, orientation & phase identification

INTRODUCTION,

STRUCTURAL TEM TECHNIQUES, 2D & 3D


Omega gate transistor (STEM ADF)

HfSiON

TiN

SiO2

SiGe

Si

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TRANSMISSION ELECTRON MICROSCOPES @ LETI USED IN THESE STUDIES

FEI Titan Themis 80-200 kVXFEG gun, Monochromator, Cs Probe Corrector,

Super X, Holography, GATAN Energy Filter, FEI

CETA CMOS Camera

FEI Titan Ultimate 80-200-300 kVXFEG gun, Monochromator, Cs Probe & Cs Image

Correctors, Holography, GATAN Energy Filter, GATAN

OneView CMOS Camera








• Software



• Summary

OUTLINE

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• Why the use of precession for measuring strain?• Originally R. Vincent, P.A. Midgley. Ultram. 53, 2 (1994)

STRAIN MEASUREMENTS IN A TEM

Precession

ap

PrécessionPrécessionsample

parallel beam (> 3nm)

No descan

a : semi-convergence angle

Precession

ap

With descan

NBED


aP = 9.7 mrad

a = 2.2 mrad

d=0.8 nm

a = 2.2 mrad

d=0.9 nm

N-PED : Higher Convergence Angle Smaller Probe size (<1nm) Higher ResolutionHigher Convergence Angle Larger disks = longer edges = better detection of circle Higher precisionMany more electron spots/disks

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• Why the use of precession for measuring strain?

• To avoid dynamical diffraction effects.

N-PED : uniform intensity within the discs3DAM Metrology Workshop | Vincent Delaye | 20/04/2018


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• References:


J-L Rouvière et al., Applied Physics Letters 103, 241913 (2013)

D. Cooper et al., Nano Letters, 15, 5289−5294 (2015)

Use of a standard Si/SiGe multilayer sampleTest structure with SiO2/Si3N4 dummy gates and

recessed SiGe S/D

N-PED precision ~ 0.02 – 0.05 %Spatial resolution ~ 1-3 nm


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• RAMAN at = 532nm (penetration depth of 1 µm)

• The frequency shift (ΔωSi-Si) for multilayer blanket corresponds to a Ge concentration of around 31%

• Assumption : the multilayer is pseudomorphic, no relaxed layer

• Can we confirm by N-PED that the blanket sample is made of biaxially strained Si69Ge31 layers?

N-PED, APPLICATION TO 3DAM SAMPLES

• N-PED experiment:

• FIB (low kV) sample preparation

• HRSTEM imaging to measure the layers

• PACBED* to measure the foil thickness: 104 nm +/- 2 nm

• N-PED acquisition and data processing (2 nm resolution)

• EDS-STEM : SiGe quantification test / RAMAN (k-factor)

• Mechanical simulation by finite element

modelling (FEM) to estimate the strain

relaxation of the FIB foil:

• 3D Model using COMSOL software

• Si/SiGe layers thicknesses : HRSTEM imaging

• FIB foil thickness : PACBED

• Composition : RAMAN

• 3D model projection over the foil thickness direction

such that the experimental N-PED strain maps can

be directly compared

IV_IMEC_DEV01 (Blanket multilayer)

• SiGe/Si/SiGe/Si on Si substrate

* Positioned Averaged Convergent Beam Electron Diffraction3DAM Metrology Workshop | Vincent Delaye | 20/04/2018

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[220]=x

[002]=z

𝜺𝒛𝒛𝑷𝑬𝑫

𝜺𝒙𝒙𝑷𝑬𝑫

Strain maps acquired by PED are shown for the [220] and [002] directions.

3D Model using COMSOL software

3D model projection over the foil thickness direction

x y

z

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A good fit is obtained between PED and FEM for a Ge content of around 31% as measured by Raman. The Ge contentmeasured by a quantitative EDS treatment in Esprit (k-factor) was 30 % using K line of the Ge peak,EDS Quantification is in good agreement with RAMAN if we use K lines for both Si and Ge elements

nm


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IV_IMEC_DEV02 (Embedded Multilayer Fins)

• In between fins = SiO2 to the top

• Surface planarized

• Arrays of fins


𝜺𝒙𝒙𝑷𝑬𝑫 𝜺𝒛𝒛

𝑷𝑬𝑫[220]=x

[002]=z

The edges of the SiGe layers exhibit a higher intensity of theHAADF signal, which corresponds to a higher Ge content. Effectof condensation during the fin etching?

30 at. % of Ge in thecenter of the SiGelayers, 50 at. % on thesides

• Ge composition map (EDS-STEM) • N-PED strain measurements

Strain maps acquired by N-PED are shown for the[220] and [002] z directions

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IV_IMEC_DEV02 (Embedded Multilayer Fins)

• In between fins = SiO2 to the top

• Surface planarized

• Arrays of fins


• Relaxation along the Fin width [220]

The strain profile along the dotted blue line shows that the exx strainranges from 1 to 1.2 % in the center of the SiGe layers. This levelcorresponds to full relaxation of the structure along the fin width.

exx for 100% relaxed(30% Ge)

exx for 50% relaxed(30% Ge)

[002]=z

𝜺𝒙𝒙𝑷𝑬𝑫 • Strain along the [002] direction

The strain profile along the dotted blue lines shows that the ezz strain ranges from 1.3 to 1.7 % in the center of the SiGe layers. This level of strain is:Higher than the one for a fully Si70Ge30 relaxed layer (ezz ~ 1.15%),Lower than the one for a Si70Ge30 fin with no relaxation along the fin length (ezz ~ 2.04%)

ezz for a full relaxation along the fin width and no relaxation along the fin length (30% Ge)

ezz for 100% biaxiallyrelaxed (30% Ge)


[220]=x







• Software



• Summary

OUTLINE

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• Purpose : User-independent, fast and efficient process for 3D reconstruction

• Electron tomography software:

• Get benefit from Graphics processing unit (GPU)

• Adapted to needle-shaped samples/on-axis tomography holder

ELECTRON TOMOGRAPHY GUI

Tilt axis projection

Sinogram


T. Printemps et al., Ultramicroscopy 160 (2016) 23–34

GUIDAR – Graphical User Interface for Denoising Alignment and Reconstruction

Automated x, z and tilt axis measurements

Apply & check alignment

Reconstruction using FBP* or SIRT** (Astra Toolbox)

* : filtered backprojection ** : simultaneous iterative reconstruction technique

z

x

Tilt axis projection

• Mix of 3 techniques

• cross-correlations between neighboring projections

• common line algorithm to get a precise shift correction in the

direction of the tilt axis

• intermediate reconstructions to precisely determine the tilt axis

and shift correction in the direction perpendicular to that axis

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FIB needle shaped specimenFIB prepared lamella (N-PED & EDS)

Acquisition IV_IMEC_DEV02 (Embedded Multilayer Fins)

• 30 projections from -90° to +90°

• Frame size: 2048x2048 pixels

• Frame time: 20sec

• Pixel size: 133pm

Ni capping

HAADF-STEM

Si

STI

SiO2

SiGe

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• Application to IMEC sample


Acquisition IV_IMEC_DEV02 (Embedded Multilayer Fins)

• 30 projections from -90° to +90°

• Frame size: 2048x2048 pixels

• Frame time: 20sec

• Pixel size: 133pm

Tilt series Aligned tilt series 3D reconstruction (SIRT)

SiGe

Si

SiO2







• Software



• Summary

OUTLINE

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• Challenge : monitor As dopant implantation process in a silicon Fin structure

• Experimental & EELS data processing setup:

• Needle shaped FIB sample preparation, on-axis holder (2050 Fischione)

• 23 HAADF STEM images & 23 fast Dual EELS maps projections (between -90° and +90°)

• PCA denoising and extraction of O K, As L2,3 and Si K elemental tilt series

ANALYTICAL ELECTRON TOMOGRAPHY


23 projections x 546x512 pixels

HAADF STEM

x 1

0^3

eV

0

10

20

30

40

x 1

0^3

1400 1600 1800 2000

eV

Si K

As L1As L1

As L2As L2As L3As L3

x 1

0^4

eV

10

20

30

40

x 1

0^4

500 550 600

eV

O K

Si

O

AsEELS STEM ROI

PCA and pseudo EELS quantification

23 sets of 3 elemental maps

23 projections x 60x90 pixels

Needle shaped FIB specimen

20 nm

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Si O AsHAADF-STEM

-90deg

-15deg

+70deg


Zero-padding

(23x111x104 pixels)23x60x90 pixels

• Use of the home-made software for

alignment (with HAADF STEM)

• Rescaling & Zero-padding of the

elemental maps

• HAADF & EELS STEM data fusion

• Application of the shifts in x and y

from the HAADF-STEM alignment

• 3D reconstruction (next slide)

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Si K

O K

As L2,3

Si K

O K

As L2,3

HAADF STEM image of the

needle shaped specimen

including the FinFET

z

x

z

x

y

y

20 nm

20 nm

20 nm

Elemental maps of

Silicon, Oxygen and

Arsenic at 70°

a) Overlay of 3D elemental volumes

b) x,y slice through the As elemental

reconstruction showing As clustering

a)

b)As L2,3

3D SIRT reconstruction obtained

with the 23 elemental projections3DAM Metrology Workshop | Vincent Delaye | 20/04/2018

8th International Workshop on Electron Energy Loss Spectroscopy and Related

Techniques, May 14th (Sun) - 19th (Fri) 2017, Okuma, Okinawa, Japan

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• Microscopy & Microanalysis US conference in August

• J. Sorrel & Z. Saghi, Correlative HAADF-STEM and EDX-STEM tomography for the 3D morphological and

elemental analysis of FinFET semiconductor devices.

• M. Jacob & Z. Saghi, Multivariate analysis and compressed sensing methods for spectroscopic electron

tomography of semiconductor devices

• Batch-processing of the 3D dataset : Spectral unmixing using MSA (NMF, VCA)

• Total variation minimization algorithm (TVM) 3D reconstructions and more

• Better quality reconstruction of the As precipitates, Fin sidewall = metrology


identification of three chemical phases in the sample: Si, SiO2 and As

EDS STEM data set

SIRT/TVM comparison


• Strain measurements

• N-PED used as a standard technique at LETI

• Combine TEM local measurement with a non-destructive technique

(RAMAN) and mechanical modelling

• (Analytical) Electron tomography

• Software : user-independent, fast and reliable

• Still some work to extract 3D quantitative information from reconstructed

volumes

SUMMARY

Leti, technology research institute

Commissariat à l’énergie atomique et aux énergies alternatives

Minatec Campus | 17 rue des Martyrs | 38054 Grenoble Cedex | France

www.leti-cea.com

“This project has received funding from the Electronic

Component Systems for European Leadership Joint

Undertaking under grant agreement No 692527. This

Joint Undertaking receives support from the European

Union’s Horizon 2020 research and innovation

programme and Netherlands, Belgium, France, Hungary,

Ireland, Denmark, Israel”

Thank you for you attention

http://www.eu-f-n.org/2018-grenoble

3rd 3DAM Metrology Workshop at Minatec Campus,

Grenoble, March, 15th 2019

Documents

2D & 3D ADVANCED TRANSMISSION ELECTRON MICROSCOPY … · 2018-08-08 · | 6 TRANSMISSION ELECTRON MICROSCOPES @ LETI USED IN THESE STUDIES FEI Titan Themis 80-200 kV XFEG gun, Monochromator,