Download Atom probe specimen preparation of semiconductors and devices

Atom probe specimen preparation
of semiconductors and devices
Baishakhi Mazumder
Intel corporation, Hillsboro
Work done @
Oak Ridge National Laboratory
University of California Santa Barbara
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Acknowledgement
Oak Ridge National Laboratory
•  Dr. Karren More
•  Dr. Debasish Mohanty
University of California Santa Barbara
•  Prof. Jim S. Speck, Prof. Umesh Mishra and Prof. Susanne Stemmer
•  Dr. Xiang Liu, Dr. David Brownie, Varistha Chobpattana
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Nanoscience applications
Commercial c plane light emitting diode
Unipolar light emitting diode
In, Ga
B. Mazumder, UCSB
Solar Cell
O.3Cojocaru-Mirédi et al., Prog.Photovolt. Res. Appl. 2015
D. Brownie, B. Mazumder et al., J. App. Phy. 2015
FIN FET Device
A. Kambham et al., IEEE 2012
Nano wire
O Moutanabbir et al., Nature 2013
Site specific needle extraction
CdTe solar cell
HEMT
Needle shape APT specimen
Li ion cathode
Two phase alloy
Nanowire
Grain boundary
Cl
Te
n-MOS device
Image courtesy:
Jonathan Poplawsky
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Focused ion beam (FIB)
•  The ion beam (Ga+) has the capability of sputtering away atoms interacting with the
beam allowing the FIB to be used as a milling tool
•  The dual beam FIB contains an electron column, as well as the ion column, which
images at an angle (typically 52°) to the ion beam.
Gallium ion
source
Electron
gun
52°
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Specimen
Site specific lift out method
Si posts
Pt dep
•  The wedge is propagated to Si-posts
in-situ
•  Multiple samples from a single wedge
lift-out possible
Site-specific region of interest (ROI)
will result in a single sample per liftout
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1µm
Sharpening wedge
1µm
80 nm
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• 
• 
• 
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Excessive material removing process
Changing the inner radius of the mask and ion beam current
Micron size wedge to R<100 nm APT needle
Tip radius and taper angle can be controlled
Gallium Damage in FIB
At 30 keV
SRIM simulation
Ni
GaN
Ga
30 keV
Damage ~10-15 nm
5 keV
Undesirable
30 keV
Damage ~ 20 nm
5 keV
K. Thompson et al.,
Ultramicroscopy 2007
Damage ~ 5 nm
Damage ~5-7 nm
•  May lead to intermixing of phases and regions of different compositions
•  May turn crystalline to amorphous material
•  May create the regions with decreased structural integrity: increase the chance of
premature failure of tip
•  A low keV milling must be used at the end to minimize the damage
• 8 Additional layer can be used to protect surface from Ga damage
Cap layer
Sacrificial layer of material to protect the original layer of interest from Ga ion damage
•  Evaporation field requirements
- Similar evaporation field is desired to minimize the risk of premature failure
- Fevap difference may cause spatial reconstruction aberrations at interfacial regions
•  Adequate adhesion
- Weak Cap/ROI interface fails to survive under high electric field
•  Potential mass spectrum peak interference
- To avoid complexity in separation of cap layer and ROI mass peak
•  Material properties
-  Very large grain size or amorphous cap material is desirable
-  Presence of grain boundary may induce undesired topography into the tip shape
formation due to milling rate difference
-  Similar or lower sputtering rate to the specimen is ideal.
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Standard APT specimen preparation
APT cap layer
APT cap layer
ROI
Substrate
ROI
Pt
Pt
Substrate
Si post
•  Bulk materials
(dual phase, grain boundaries, precipitate etc)
•  Thin films
•  Implanted region
•  Multi layers (Quantum wells, etc)
•  3D structures (Fin FET, Transistors etc.)
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Advanced sample preparation
InGaN/GaN Solar cell
•  Thin film –volume limitation
- Dopant concentration measurement
- Clustering within thin film
20 nm
•  Dissimilar field materials multilayer
•  Symmetric stack with high and low field
materials (MRAM, MTJ etc)
Y. Hu et al., App. Phy. Lett. 2012, UCSB
Ni
HfO2
Al2O3
InGaAs
GaAs
•  Analysis yield (reducing electrostatic stress)
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Ta
MgO
CoFeB
Ta
CoFeB
MgO
CoFeB
Ta
Cross section sample preparation
APT cap layer
Pt
APT cap layer
ROI
Substrate
Substrate
APT cap layer
ROI
ROI
Substrate
APT cap layer
ROI
APT cap layer
Pt
Si post
HfO2/InGaAs
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HfO2
In
Ga
Advanced sample preparation
•  Presence of thick insulating (thermally or electrically) material beneath ROI
- Alternative channel, InGaAs/Dielectric (Al2O3, SiO2)
- CdTe solar cell grown on glass
CdTe
CdS
TCO
Glass
•  Weak or problematic materials or interfaces exist
between sample surface and ROI
Image courtesy: J. Poplawsky, ORNL
•  Presence of different evaporation field material can lead
to tip shape distortion, resultant effects on data reconstruction, induce artifacts
Cr
Co
Cu
Co
Cr
Si
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Intermixing at the interface FCo>FoCr>FCu
D. Larson et al., Ultramicroscopy, 2011
Backside sample preparation
Ga ion mill
ROI
Substrate
APT cap layer
ROI
Substrate
Substrate
ROI
APT
cap layer
APT cap layer
APT cap layer
(1.5-2 µm)
Pt
Pt
Si post
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Some other applications
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Nano wire sample preparation
Dimension – 100-125 nm, length ~1µm
InGaN MQW
R. Shivraman PhD thesis, UCSB
InGaP/GaAs core shell
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Dieter Isheim et al., The journal of Physical Chemistry C
Nano wire sample preparation
H Blumtritt et al.,Nanotechnology 2014
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Battery (Cathode) sample preparation
APT needle
NMC cathode
100 nm
Microstructure of LMR cathode
5 µm
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Final APT needle
1 µm
100 nm
LMR Cathode sample preparation
Select a particle
LMR oxide particles
on Si substrate
10 µm
2.5 µm
Lift-out using omniprobe
2.5 µm
Transfer to silicon microtip
LMR oxide
Pt weld
LMR oxide particle
on silicon microtip 2.5 µm
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Final needle
200 nm
Transistor sample preparation
FIN FET transistor
PMOS transistor
Toshiba analysis
corporation
http://
www.nanoanalysis.c
o.jp/en/business/
case_example_137.
html
B
SiO
Si FIN FET
Si/SiGe interface study
A.J. Martin et al, 161, Ultramicroscopy 2016
A.20Kambham et al, Ultramicroscopy 2011
Correlative TEM-APT sample preparation
• 
• 
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Direct correlation and comparison
Artifacts from one technique
Better Reconstruction
Interface quality comparison etc.
100 nm
M. Herbig et al., Ultramicroscopy 2015
Growth direction
LT GaN
Al2O3
GaN
10 nm
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3 nm
B. Mazumder et al., J. Appl. Phys. 2014
J. Li et al., Solar energy materials and Solar cells 2015
Correlative TEM-APT sample preparation
TEM grid
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Cu tube
Correlative TEM-APT sample preparation
TEM grid
Cu tube
M. Herbig et al., Ultramicroscopy 2015
Hummingbird TEM
tomography holder
Fishione tomography holder
D.J. Larson et al.,
Local Electrode Atom Probe Tomography
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Springer publication
Summary
•  Site specific sample preparation from a wide range of materials
•  Enable needle preparation from variety of sample geometry
•  Permits accurate selection of the specimen radius and taper angle (to a lesser
extent)
•  The ability to probe a wide spectrum of systems have dramatically improved with
the use of FIB based APT specimen fabrication methods.
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Thank you
Video courtesy : Cameca Instruments
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Cross section sample preparation
D.J. Larson et. al,
Local Electrode Atom Probe Tomography
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Springer publication
Backside sample preparation
D.J. Larson et. al,
Local Electrode Atom Probe Tomography
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Springer publication