ald an enabler for nanoscience and nanotechnology gordon harvard revied amide compounds
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8/17/2019 ALD an Enabler for Nanoscience and Nanotechnology Gordon Harvard Revied Amide Compounds
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Atomic Layer Deposition (ALD): An Enabler
for Nanoscience and Nanotechnology
Roy G. Gordon
Harvard University
Cambridge, MA
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Definitions of Chemical Vapor Deposition (CVD)and Atomic Layer Deposition (ALD)
Structures and materials made by ALD
Properties needed for CVD and ALD precursors:
Volatility, Stability, Reactivity
How to design those properties into precursors:
metal amidinates
High-k insulators: La2O3, LaAlO3
Outline
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Chemical Vapor Deposition (CVD)
One or more gases or vapors react to form a solid product
Reaction started byheat
mixing 2 vapors
plasma
Solid product can be afilm
particle
nanowire
nanotube
precursor vapors
byproductvapors
substrate
film
Heater
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Benefits of ALD:
• Atomic level of control over film composition⇒nanolaminates and multi-component materials
• Uniform thickness over large areas and inside narrow holes
• Very smooth surfaces (for amorphous films)• High density and few defects or pinholes
• Low deposition temperatures (for very reactive precursors)
• Pure films (for suitably reactive precursors)
Sequential, self-limiting surface reactions make alternating layers:
Atomic Layer Deposition (ALD)
Heated area =
deposition zone
Precursor 1
Precursor 2
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Typical ALD Reaction for Oxides
OH OH OH
ML2
ML2
ML2
ML
O
ML
O
ML
O
HL HLHL
ML
OML
O
ML
O
H2O
H2OH2O
MOH
OMOH
O
MOH
O
HLHL
HL
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Definitions of Chemical Vapor Deposition (CVD)and Atomic Layer Deposition (ALD)
Structures and materials made by ALD
Properties needed for CVD and ALD precursors:
Volatility, Stability, Reactivity
How to design those properties into precursors:
metal amidinates
High-k insulators: La2O3, LaAlO3
Outline
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Lining and Fill ing Holes by ALD
4 cycles 12 cycles
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Nanopores by ALD
Ion Mill ing
Ion Milling + ALD
May be used for rapid sequencing of DNA
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Coatings on the Outside of Particles
ALD AlN coating
ZnS particles
Used in electroluminescent back-lights for displays
in cell-phones and many other devices.
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Photonic Crystals by ALD
f
500nm
1) Form crystals of silica spheres.
2) ALD of Ta2O5 between the spheres
3) Convert to Ta3N5 in NH3
4) Dissolve the silica spheres in HF
The resulting photonic crystals may be able to control light,
the way semiconductors control electron transport.
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Nano-Dots by ALD
ALD ruthenium
on aluminum oxide
nucleation density is
~ 20 x higher than previous
metal nanocrystals
40 nm scale bar; 10 nm in insertmay be applied to
flash memories
diameters ~1 to 2 nm,
~ 5 to 10 atoms across
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Nanobeads by ALD
after 500 cycles of Al2O3 after 500 cycles of iron
Growth on Single-walled Carbon Nanotubes
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Alumina Nanotubes on Carbon Nanotubes
100 nm diameter 21 nm diameter 7 nm diameter
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Nano-Coaxial Cable or Transistor
Conducting tungsten nitride (WN) concentrically around
insulating aluminum oxide (Al2O3) concentrically around
a conducting carbon nanotube.
Carbon Al2O3 WN Al2O3WN
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Elements included in ALD Materials
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br KrRb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Green = Element included in at least 1 ALD Material
Red = Element not included in any ALD Material
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Oxides Made by ALD
H HeLi Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br KrRb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I XeCs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At RnFr Ra Ac
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Green = ALD process known for an Oxide of the Element
Red = no process known for ALD of any Oxide of the Element
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Pure Elements Made by ALD
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br KrRb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Green = ALD processes known for 16 Pure Elements
Red = no process known for ALD of the Element
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Nitrides Made by ALD
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br KrRb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Green = ALD processes known for a Nitride of the Element
Red = no process known for ALD of a Nitride of the Element
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Sulfides Made by ALD
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br KrRb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Green = ALD processes known for a Sulfide of the Element
Red = no process known for ALD of a Sulf ide of the Element
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Carbides Made by ALD
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br KrRb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Green = ALD processes known for a Carbide of the Element
Red = no process known for ALD of a Carbide of the Element
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Fluorides Made by ALD
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br KrRb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr
Green = ALD processes known for a Fluoride of the Element
Red = no process known for ALD of a Fluoride of the Element
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Current Applications of ALDElectroluminescent displays (Al2O3, AlN, ZnS)Read/Write heads in magnetic disk storage (Al2O3)Insulators in capacitors in DRAMs (Al2O3, HfO2)
Insulation and spacer layers in microelectronics (SiO2, Si3N4)Metal/insulator in transistor gates (TaN/HfO2)Planar waveguides and optical filters (SiO2, TiO2)
Likely Future Applications of ALDInsulators in microelectronic capacitors (Ta2O5, SrTiO3, LaLuO3)Diffusion barriers for copper in interconnects (WN, TaN, Mn) Adhesion and seed layers for interconnects (Co4N, Ru, Cu)Sealing pores in low-k dielectrics (SiO2)Magnetic disk storage (Al2O3, Fe, Co, Ni, Cu, Ru, Mn, Pt)Nano-Electronics
Catalysts . . .
Applications of ALD
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Definitions of Chemical Vapor Deposition (CVD)and Atomic Layer Deposition (ALD)
Structures and materials made by ALD
Properties needed for CVD and ALD precursors:
Volatility, Stability, Reactivity
How to design those properties into precursors:
metal amidinates
High-k insulators: La2O3, LaAlO3
Outline
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Criteria for Both CVD & ALD Precursors
•Sufficient volatility (> 0.1 Torr at T < 200 oC)
•No thermal decomposition during vaporization
•Liquid at vaporization temperature
•Preferably liquid at room temperature
or soluble in an inert solvent
•Precursors and byproducts don’t etch fi lms
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Some precursors work only in CVD, but not ALD:
Ni(CO)4, W(CO)6, many alkoxides
Some precursors work in both CVD and ALD:
many beta-diketonates and amidinates
Usefulness of Precursors for CVD & ALD
CVD
ALDMost ALD precursors
also work in CVD
Some CVD precursors
also work in ALD
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Definitions of Chemical Vapor Deposition (CVD)and Atomic Layer Deposition (ALD)
Structures and materials made by ALD
Properties needed for CVD and ALD precursors:
Volatility, Stability, Reactivity
How to design those properties into precursors:
metal amidinates
High-k insulators: La2O3, LaAlO3
Outline
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Metal(II) Amidinates
R1
and R3
= alkyl groups Acetamidinates: R2 = CH3
N
M
N
R1
R2
R3
N
N
R2
R1
R3
monomer dimer
N
M
N
R2
N N
M
R3
R1
R3
R1
N N
R1R3
N
N
R1
R3
R2
R2
R2
Formamidinates: R2
= H
The choices of Rn affect the volatility, reactivity and stabil ity.
M-N bonds are generally reactive to H2O, NH3, H2, etc.
The chelate structure adds to the thermal stabili ty.
Propionamidinates: R2 = CH2CH3
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1351181001038378727473736569ionic radius
ddmtert-pentyl2
Bi
m
Zn
m
Ge
m
dn-propyl2
BaSr CaMnFeMgCr CoNiR1, R3
ppdddmEt-tert-Bu
ppddddmmmisopropyl2
dddmmmccctert-butyl2
Increasing “ size” of metal atom
I n
c r e a s i n g
l i g
a n d
b u l k
d = reactive, volatile dimer
Structures of Metal Bis-Acetamidinates
p = non-volatile polymer
m = more reactive, less stable, volatile monomer
c = crowded, less reactive, more stable, volatile monomer
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Metal(III) Amidinates
R1 and R3 = alkyl groups
Formamidinates: R2 = H
Acetamidinates: R2 = CH3
M
N N
N N
NN
C C
CR
3R
1
R3
R1
R1
R3
R2
R2
R2
monomer
Structures of dimers are unknown, probably bridged
Propionamidinates: R2 = CH2CH3
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ddmMe2
pmmmmmEt2
La
p
d
m
c
Ce
c
Pr
m
Nd
c
Eu
c
Gd
m
Y
d
m
c
V
c
Co
c
mmmmcn-Pr 2
LuSbScRuTiFeCr Ga AlR1,R3
mEt-
tBu
cccccccciso-
Pr 2
cnntert-
Bu2
Increasing size of metal atom
I n c r e a s i n g
l i g a n
d
b u l k
m = more reactive monomer
d = low-volatili ty dimer
Structures of Metal(III) Tris-Amidinates
p = non-volatile polymer
c = crowded, less reactive monomer n = non-existent
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Models for Lanthanum and Scandium Amidinates
La precursor reacts
quickly with surface OH
Sc precursor reacts
slowly with surface OH
La ion is large, so 3 amidinateligands are not crowded
Sc ion is small, so 3 amidinateligands are crowded
La
Sc
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Zr(amd)4 and Hf(amd)4
Metal(IV) Tetra-Amidinates
Require small Rn groups
such as H and CH3
CH3
N
N CH3
H
H3C N
N
CH3
H
CH3N
N
CH3
H
CH3
N
NH3C
H
Hf
Zr amidinate is much more stable
than Zr amide, Zr(NEtMe)4
Thermal decomposition at 200o
C
Greater stabili ty of amidinates is
due to chelate structure (2 metal-
nitrogen bonds instead of one)
O tli
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Definitions of Chemical Vapor Deposition (CVD)and Atomic Layer Deposition (ALD)
Structures and materials made by ALD
Properties needed for CVD and ALD precursors:
Volatility, Stability, Reactivity
How to design those properties into precursors:metal amidinates
High-k insulators: La2O
3, LaAlO
3
Outline
Th i t i A l i f
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Thermogravimetric Analysis of
Lanthanum Amidinates
N
H
C N
N
CHNN
HC
N La
NC
N
N
CNN
C
N La
CH3
CH3H3C
NC
N
N
CNN
C
N La
CH3
CH3H3C
H3C CH3
CH3
CH3CH3
H3C
=> Vaporization temperature increases with molecular mass
V P f L th P
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Vapor Pressures of Lanthanum Precursors
=> La(iPr 2-fmd)3 is most
volatile La compound known,
60 mTorr at 100 oC
La(iPrCp)3
NHC
N
N
CHNN
HC
N La
0.1
Torr
ALD f L O
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ALD of La2O3
=> 0.16 nm per cycle
=> negligible delay
in nucleation on SiH
N
HC N
N
CHNN
HC
N La
tris(N,N’-diisopropyl-formamidinato)lanthanum
(iPr 2-fmd)3La
Precursors:H2O and
Growth per La Cycle for ALD LaAlO
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Growth per La Cycle for ALD LaAlO3
Bubbler temperature 90 to 120 oC
Substrate temperature 300 oC
Growth even at bubbler
temperature <100 oC
=> ALD saturation at0.08 nm per La cycle
N
HC N
N
CHNN
HC
N La
tris(N,N’-diisopropyl-formamidinato)lanthanum
(iPr 2-fmd)3La
Precursors:Me3 Al, H2O and
120 oC110 oC
100 oC
90 oC
Composition of ALD La Al O
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Composition of ALD Lax Al1-xO3/2
Growth conditions:
Bubbler temperature 120 oC
Substrate temperature 300 oC
=> Composition control
by changing ratio of
precursor doses
=> 2 x as many Al atoms
as La atoms per dose
N
HC N
N
CHNN
HC
N La
tris(N,N’-diisopropyl-formamidinato)lanthanum
(iPr 2-fmd)3La
Precursors:Me3 Al, H2O and
Precursor Reactivity with SiH Surface by IR
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Precursor Reactivity with SiH Surface by IR
=> Completely uniform surface coverage by La amidinate
Hf alkylamide only
reacts with half of
the Si-H bonds onthe surface even
after many cycles
La amidinate reactswith nearly all the
Si-H bonds in only
3 cycles
Details of the infrared data were given at AVS Conference ALD 2007 by
J. Kwon, M. Dai, E. Langereis, Y. Chabal, K.-H. Kim and R. G. Gordon.
TEMs of ALD LaAlO and GdScO
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TEMs of ALD LaAlO3 and GdScO3
=> Sharp interfaces with silicon without interlayers
=> Uniform nucleation and thickness
LaAlO3
Si2 nm
Leakage Current through ALD La O
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Leakage Current through ALD La2O3
Vapor source: a solution of the La precursor (mp 194o
C)vaporized with an MKS MDD liquid delivery system
Low leakage current similar to films made from a bubbler.
=> negligible carbon contamination from solvent
C i f l k
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Harvard University
Comparison of leakage
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.010
-8
10-6
10-4
10-2
100
102
SiO2
ALD LaAlO3
ALD GdScO3
ALD LaScO3
ALD HfO2 from IMEC (Ref.1)
MOCVD HfO2 from IMEC (Ref.2)
ALD HfO2 from IBM (Ref.3)
Sputter HfO2 (Ref.4)
L e a k a g e (
A / c m
2 )
EOT (nm, |Vg-V
fb|=1V)
Summary
8/17/2019 ALD an Enabler for Nanoscience and Nanotechnology Gordon Harvard Revied Amide Compounds
http://slidepdf.com/reader/full/ald-an-enabler-for-nanoscience-and-nanotechnology-gordon-harvard-revied-amide 44/45
Harvard University
Summary
ALD requires volatile precursors with self-limited reactivityand high thermal stabili ty
Precursors with these properties are known for mostelements
ALD is a proven process with many current applications
Many more uses for ALD are expected in the future
Acknowledgements
8/17/2019 ALD an Enabler for Nanoscience and Nanotechnology Gordon Harvard Revied Amide Compounds
http://slidepdf.com/reader/full/ald-an-enabler-for-nanoscience-and-nanotechnology-gordon-harvard-revied-amide 45/45
Harvard University
AcknowledgementsMetals: Booyong Lim, Antti Rahtu, Jin-Seong Park, Venkateswara Pallem
Cu, Co: Zhengwen Li, Séan Barry, Don Keun Lee, Harish Bhandari, Hoon Kim
Ruthenium: Huazhi Li, Titta Aaltonen, Jun Ni
Metal Nitrides: Jill Becker, Seigi Suh, Esther Kim,
Kyoung
young
-ha
a Kim
Metal oxides: Dennis Hausmann, Philippe de Rouffignac, Jin-Seong Park,
Kyoung
young
-ha
a Kim, Leo Rodriguez, Mike Coulter, Jean Sébastien Lehn, Sheng
Xu, Hongtao Wang, Yiqun Liu
TEM: Damon Farmer; Hongtao Wang, SEMATECH, Applied Materials
DRAM trenches supplied by Infineon Qimonda)
La, Co, Cu and Ru precursors supplied by Rohm and Haas Electronic Materials
SiO
2
and W precursors supplied by Sigma-Aldrich Company
SEMs and Electrical Analysis by Daniel Josell, NIST
Supported by the US National Science Foundation and Intel Corporation