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TRANSCRIPT
Vapor phase deposition technologies
Physical Vapor Deposition (PVD) – sputtering –
Chemical Vapor Deposition (CVD)
Energetic ions! Heat!
/Applied Physics - Erwin Kessels
g
More applications have stricter requirements on
1. Precise growth and thickness control
2 Hi h f lit / t2. High conformality/step coverage
3. Good uniformity on large substrates
4. Low substrate temperatures
/Applied Physics - Erwin Kessels
Very demanding applications
Nanoelectronics Photovoltaics
fProtective thin films Flexible electronics
/Applied Physics - Erwin Kessels
CMOS scaling in nanoelectronics
??????graphenegraphene
Active Area
Gate FieldSpacers
Active Area
Gate FieldSpacers
Active Area
Gate FieldSpacers
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??????Active Area
Gate FieldSpacers
Active Area
Gate FieldSpacers
Active Area
Gate FieldSpacers
Ge/IIIVGe/IIIV
nanowiresnanowires
g pg p
HfO
metal gatemetal gate
FinFETFinFET
L=35nm
SiGe
L=35nmL=35nm
SiGe
strainstrain
HfO 2high high --
timesilicidesilicide
USJUSJ
Timee
Courtesy of Marc Heyns, IMEC/Applied Physics - Erwin Kessels
Field-effect transistor: replacing SiO2 by HfO2
32 nm
Thermally grown SiO2Thermally grown SiO2
/Applied Physics - Erwin Kessels
Precise deposition of nanometer-thick Hf-based oxides
www.chipworks .com
Field-effect transistor: going from 2D to 3D gates
22 nm
Precise deposition of nanometer-thick Hf-based oxides with excellent conformality
/Applied Physics - Erwin Kessels
with excellent conformality
www.chipworks .com
Outline
1. Atomic layer deposition (ALD): basics and key features
2. ALD equipment
3. Materials & ALD surface chemistries
4. Some applications of ALD
5. Recent developments in high-throughput ALD
/Applied Physics - Erwin Kessels
Atomic Layer Deposition (ALD)
• Reactants (precursors) are pulsed into reactor alternately and cycle-wise (ABAB..)
• Precursors react through saturative (self-limiting) surface reactions
• A sub-monolayer of material deposited per cycle
/Applied Physics - Erwin Kessels
ALD of Al2O3 films: Al(CH3)3 - H2O process
/Applied Physics - Erwin Kessels
Thickness vs. number of cycles
Film thickness is ruledby the number of cycles chosen
30
1. Al(CH3)3
2 SiH {N(C H )}
H3C AlCH3
CH3
N(C2H5)2 301. Al2O3
2. SiO2
3. Ta2O5m)
2. SiH2{N(C2H5)}2
3 T {N(CH ) }N(CH3)2
SiH H
N(C2H5)2
202 5
4. ZnO2
5. TiO2ne
ss (n
m3. Ta{N(CH3)2}5(H3C)2N Ta
N(CH3)2
N(CH3)2
( 3)2
N(CH3)2
10
Thic
kn
4. Zn(CH2CH3)2H3C
H2C
Zn
H2C
CH3
0 50 100 150 200 2500
ALD C l
5. Ti(Cp*)(OCH3)3
TiH3CO OC
OCH3
H3CCH3
CH3
H3C CH3
+
/Applied Physics - Erwin KesselsPotts et al., J. Electrochem. Soc., 157, P66 ( 2010).Dingemans et al., J. Electrochem. Soc. 159, H277 (2012)
ALD CyclesH3CO OCH3+ H2O, O3, or O2 plasma
Key features of ALD
1. Control of film growth and thickness‘Digital’ thickness control
2. High conformality/step coverageSelf-limiting surface reactions
3 G d if it l b t t3. Good uniformity on large substrates300 mm and even bigger
4. Low substrate temperaturespBetween 25 - 400 °C
5. Multilayer structures and nanolaminatesEasy to alternate between processes
6. Large set of materials and processesMany different materials demonstratedMany different materials demonstrated
/Applied Physics - Erwin Kessels
Line-of-sight vs. conformal growth
/Applied Physics - Erwin Kessels
Materials deposited ALD
/Applied Physics - Erwin KesselsPuurunen, J. Appl. Phys. 97, 121301 (2005)Miikkulainen et al., J. Appl. Phys. 113, 021301 (2013).
Outline
1. Atomic layer deposition (ALD): basics and key features
2. ALD equipment
3. Materials & ALD surface chemistries
4. Some applications of ALD
5. Recent developments in high-throughput ALD
/Applied Physics - Erwin Kessels
Single wafer ALD reactor
Shower head reactor(warm or hot wall reactor)
Flow-type reactor(hot wall reactor)
• Temporal ALD
P l t i f• Pulse-train of precursors
• Reactor pressure 1-10 Torr
• Applications: semiconductor (logic)
/Applied Physics - Erwin Kessels
pp ( g )
Batch ALD reactor
Temporal ALD
Batch reactor
• Temporal ALD
• Typically 50-500 substrates in a single deposition run
• Single-side deposition can be challengingg p g g
• Applications: semiconductor (memory), displays,
solar cells, etc.
/Applied Physics - Erwin Kessels
Plasma ALD reactors
Plasma-assisted ALD can yield additional benefits for specific applications:1. Improved material properties 2. Deposition at lower temperatures (also room temperature)
Direct plasma Remote plasma
p p ( p )3. Higher growth rates/cycle and shorter cycle times4. More versatility/freedom in process and materials etc.
Direct plasmaSubstrate part of plasma creation zone
Remote plasmaSubstrate “downstream” of plasma creation
zone
/Applied Physics - Erwin KesselsHeil et al., J. Vac. Sci. Technol. A 25, 1357 (2007).Profijt et al., J. Vac. Sci. Technol. A 29 050801 (2011)
Plasma-based chemistry (metal oxides)
1.Al(CH3)3
2.
H3C AlCH3
CH3
Si
N(C2H5)2
2 0 Al2O3 TiO2 - Ti(OiPr)4
e)
SiH2{N(C2H5)}2
3.Ta{N(CH3)2}5 (H3C)2N Ta
(C )
N(CH3)2
N(CH3)2
SiH H
N(C2H5)2
1.6
2.0 2 3 2 ( )4
SiO2 TiO2 - Ti(CpMe)(OiPr)3
Ta2O5 TiO2 - Ti(Cp*)(OMe)3
e (Å
/cyc
le
( 3)2 5
4.Ti(OiPr)4
N(CH3)2N(CH3)2
Ti i
OiPr0.8
1.2
per C
ycle
4
5.Ti(CpMe)(OiPr)3 Ti
TiiPrO OiPr
OiPr
CH3
0 0
0.4G
row
th
3
6.Ti(Cp*)(OCH )
TiiPrO OiPr
OiPr
H3CCH3
CH3
0 50 100 150 200 250 3000.0
Substrate Temperature (°C)
/Applied Physics - Erwin Kessels
Ti(Cp*)(OCH3)3Ti
H3CO OCH3
OCH3
H3C CH3
Potts et al., J. Electrochem. Soc., 157, P66 ( 2010).Dingemans et al., J. Electrochem. Soc. 159, H277 (2012)
Oxford Instruments OpAL reactor – Plasma ALD
/Applied Physics - Erwin Kessels
ALD equipment suppliers (incomplete list)
Semiconductor Solar / R2RR&D / Pilot
/Applied Physics - Erwin Kessels
Outline
1. Atomic layer deposition (ALD): basics and key features
2. ALD equipment
3. Materials & ALD surface chemistries
4. Some applications of ALD
5. Recent developments in high-throughput ALD
/Applied Physics - Erwin Kessels
Metalorganic and H2O: ligand exchange (Al2O3)
Al(CH3)3 exposure Purge
10-8
H Ory s
igna
l (A)
Al(C
H3)
3
Al(C
H3)
3
Al(C
H3)
3
Al(C
H3)
3
H2O
H2O
H2O
H2O
10-8
H Ory s
igna
l (A)
10-8
H Ory s
igna
l (A)
Al(C
H3)
3
Al(C
H3)
3
Al(C
H3)
3
Al(C
H3)
3
H2O
H2O
H2O
H2O
10-10
10-9H2O
spec
trom
etr
CH410-10
10-9H2O
spec
trom
etr
CH410-10
10-9H2O
spec
trom
etr
CH4AlOH*+ Al(CH3)3 AlOAl(CH3)2* + CH4
Cycle0 25 50 75 100
10-11Mas
s
Time (s)
4
0 25 50 75 10010-11M
ass
Time (s)
4
0 25 50 75 10010-11M
ass
Time (s)
4AlOH Al(CH3)3 AlOAl(CH3)2 CH4
Surface chemistry rules ALD process:
ligand exchange between Al(CH ) and
AlOH* + CH4AlCH3* + H2O
ligand exchange between Al(CH3)3 and –OH surface groups and H2O and –CH3
surface groups leads to CH4 reaction products* are surface species
H2O exposurePurge/Applied Physics - Erwin Kessels
Metalorganic and H2O: ligand exchange (Al2O3)
Al(CH3)3 exposure Purge
10-8
H Ory s
igna
l (A)
Al(C
H3)
3
Al(C
H3)
3
Al(C
H3)
3
Al(C
H3)
3
H2O
H2O
H2O
H2O
10-8
H Ory s
igna
l (A)
10-8
H Ory s
igna
l (A)
Al(C
H3)
3
Al(C
H3)
3
Al(C
H3)
3
Al(C
H3)
3
H2O
H2O
H2O
H2O
10-10
10-9H2O
spec
trom
etr
CH410-10
10-9H2O
spec
trom
etr
CH410-10
10-9H2O
spec
trom
etr
CH4
Cycle0 25 50 75 100
10-11Mas
s
Time (s)
4
0 25 50 75 10010-11M
ass
Time (s)
4
0 25 50 75 10010-11M
ass
Time (s)
4
Surface chemistry rules ALD process:
ligand exchange between Al(CH ) andligand exchange between Al(CH3)3 and –OH surface groups and H2O and –CH3
surface groups leads to CH4 reaction products
H2O exposurePurge/Applied Physics - Erwin Kessels
Metalorganic and H2O: ligand exchange (Al2O3)
4x10-5
rban
ce
2940 cm-1 1207 cm-1
Al(CH3)3chemisorption
Al(CH3)3 exposure Purge
frare
d ab
so OH stretching
CHxstretching
CHxdeformation
2940 cm 1 1207 cm 1
H O
4000 3500 3000 2500 2000 1500 1000
In
Wavenumber (cm-1)
H2Oexposure
Cycle
Surface chemistry rules ALD process:
Surface alternately covered by –OHSurface alternately covered by –OH surface groups and –CH3 surface groups
/Applied Physics - Erwin Kessels
H2O exposurePurge
Metalorganic and H2O: ligand exchange (Al2O3)
0.8
1.2
Cyc
le (Å
)Al(CH3)3 exposure Purge
0.4
owth
per
C
0 20 40 600.0
Gro
Al(CH3)3 dose (ms)Cycle
Conditions such that precursors react through saturative surface reactions:
Al(CH3)3 does not react with –CH3surface groups
/Applied Physics - Erwin Kessels
H2O exposurePurge
Metalorganic and H2O: ligand exchange (Al2O3)
0 8
1.2
ycle
(Å)Al(CH3)3 exposure Purge
0.4
0.8
wth
per
Cy
0 20 40 60 800.0G
row
H2O dose (ms)Cycle
Conditions such that precursors react through saturative surface reactions:
H2O does not react with –OH surface groups
/Applied Physics - Erwin Kessels
H2O exposurePurge
Metalorganic and H2O: ligand exchange (Al2O3)
1.2
1.6
cle
(Å)
Al(CH3)3 exposure Purge
0.4
0.8
wth
per
Cyc
CVD+ALD ALD
0 2 4 6 80.0G
row
Purge after Al(CH3)3 dose (s)Cycle
Precursors and reactants should be very well evacuated/separated from
reactor before pulsing the next precursor/reaction:
Otherwise parasitic CVD
/Applied Physics - Erwin Kessels
H2O exposurePurge
ALD process: saturation curves (Al2O3)
(a)
0.15
0.20
(nm
/cyc
le) Thermal ALD - Al(CH3)3 & H2O
0.05
0.10
wth
per
Cyc
le (
CVDSubsaturation CVD
0 20le) (b)
0 20 40 60 80 1000.00G
row
Dose time (ms)0 1 2 3 4 5
Purge time (s)0 20 40 60 80
H2O dose (ms)0 1 2 3
Purge time (s)Plasma ALD - Al(CH3)3 & O2 plasma
0.10
0.15
0.20
Cyc
le (n
m/c
ycl
Subsaturation
0 20 40 60 80 1000.00
0.05
Gro
wth
per
C
0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3
CVD
/Applied Physics - Erwin Kessels
Dose time (ms) Purge time (s) Plasma time (s) Purge time (s)
ALD process: substrate temperature (Al2O3)
e)
0.2 Plasma ALD Thermal ALD
e (n
m/c
ycle
(a)
0.0
0.1
Gro
wth
rate
3456
(b)
per
cyc
le
cm-2)
0123
# A
l ato
ms
(10
15 c
0 100 200 300 4000
Substrate temperature (oC)
AlOH* + Al(CH3)3 AlOAl(CH3)2* + CH4
/Applied Physics - Erwin Kessels
( 3)3 ( 3)2 4
AlOH* + CH4AlCH3* + H2O Van Hemmen et al., J. Electrochem. Soc. 154, G165 (2007)Potts et al., J. Electrochem. Soc., 157, P66 ( 2010).
ALD process: substrate temperature (ideal case)
ALD Temperature Window
A. CondensationB InsufficientWindow
Cyc
le A C
AC
B. Insufficient thermal energy
C. CVD
wth
per
C
B
D. Evaporation
H2O
Gro
w B DBD OH OH O∆T
Substrate Temperature Substrate/film surface
/Applied Physics - Erwin Kessels
Metal halide: ligand exchange (HfO2 and TiN)
HfOH* + HfCl HfOHfCl * + HCl
Metal oxides: ligand exchange
HfOH* + HfCl4 HfOHfCl3* + HCl
HfOH* + HClHfCl* + H2O
TiNH* + TiCl TiNTiCl * + HCl
Metals nitrides: ligand exchange
TiNH + TiCl4 TiNTiCl3 + HCl
TiNH2* + HClTiCl* + NH3
/Applied Physics - Erwin Kessels * are surface species
Metals: combustion (Pt) and reduction (W)
Noble metals: combustion by chemisorbed O2
3 O* + 2 (MeCp)PtMe3 2 (MeCp)PtMe2* + CH4 + CO2 + H2O
2 Pt* + 3 O* + 16 CO2 + 13 H2O2 (MeCp)PtMe2* + 24 O2Pt
Metals: fluorosilane elimination reactions
WSiF H* + WF WWF * + SiF HWSiF2H + WF6 WWF5 + SiF3H
WSiF2H* + SiF3H + 2H2WWF5* + Si2H6
/Applied Physics - Erwin Kessels * are surface species
Plasma-based chemistry (Al2O3 and TiN)
Metal oxides: combustion
AlOH*+ Al(CH3)3 AlOAl(CH3)2* + CH4
AlOH* + CO2 + H2OAlCH3* + 4O
Metal nitrides: ligand exchange and reduction
TiNH* + TiCl TiNTiCl * + HClTiNH + TiCl4 TiNTiCl3 + HCl
TiNH2* + HClTiCl* + 3H + N
/Applied Physics - Erwin Kessels * are surface species
ALD of doped films, ternary compounds, etc.
/Applied Physics - Erwin Kessels
ALD of Al-doped ZnO films
Zn(C2H5)2 + H2O ZnO + 2 C2H6ZnO
ZnO:Al n cycles ZnO + m cycles Al2O3
101
150 ºC
Al2O3 TMA or DMAI + H2O
100
TMA
c
m)
2
10-1
sist
ivity (
0 5 10 15 20 25 3010-3
10-2
Res
DMAI
/Applied Physics - Erwin Kessels Wu et al., J. Appl. Phys. 114, 024308 (2013)
0 5 10 15 20 25 30
Al fraction (at.%)
Outline
1. Atomic layer deposition (ALD): basics and key features
2. ALD equipment
3. Materials & ALD surface chemistries
4. Some applications of ALD
5. Recent developments in high-throughput ALD
/Applied Physics - Erwin Kessels
Thin-film electroluminescent (TFEL) displays
New large-area display in 1983
Atomic layer deposited ZnS:Mn
1974 First patent on ALD filed by Tuomo Suntala1983 Introduction of first ALD (non)-transparent inorganic TFEL display
Since 1989 Commercial production of ALD-TFEL displays by Planar
/Applied Physics - Erwin Kessels T. Suntola, Mater. Sci. Rep. 4, 261 (1989)
Encapsulation of OLED Devices
No encapsulation
Thin-film-encapsulated OLEDs after testing
40 nm ALD Al2O3 film
Thin film encapsulation requires:• low deposition temperatures• low water vapor transmission rates• low pinhole (black spot) density
/Applied Physics - Erwin KesselsLangereis et al., Appl. Phys. Lett. 89, 081915 (2006).Keuning et al., J. Vac. Sci. Technol. A 30, 01A131 (2012).
Defect (dust particle) encapsulation
/Applied Physics - Erwin Kessels Courtesy of Jian Jim Wang (NanoNuvo Corporation, USA)
ALD films for photovoltaics
CIGS solar cells Dye-sensitizedsolar cells
c-Si solar cellsOrganic solar cells
Buffer layers
Zn(O S)
Barrier layer
Al O HfO
Surfacepassivation
Transparent conductive oxide
On the verge of
Zn(O,S)(Zn,Mg)O
In2O3
l
Al2O3, HfO2, TiO2, etc.
PhotoanodeZ O S O
pAl2O3ZnO:Al
Electron selective layer
industrial application
High-throughput equipment
Encapsulation
Al2O3
ZnO, SnO2, TiO2, etc.
Blocking layer Encapsulation
Al2O3, ZnO, TiO2
selective layer
/Applied Physics - Erwin Kessels Van Delft et al., Semicond. Sci. Technol. 27, 074002 (2012).
q pavailable
g y
HfO2, SnO2, TiO2
pAl2O3
Outline
1. Atomic layer deposition (ALD): basics and key features
2. ALD equipment
3. Materials & ALD surface chemistries
4. Some applications of ALD
5. Recent developments in high-throughput ALD
/Applied Physics - Erwin Kessels
Large substrate ALD reactors
• Temporal ALD
• Can be (inline) single wafer or batch reactor
• Substrate size up to 120 x 120 cm2
• Applications: Thin-film transistors, encapsulation,
CIGS solar cells, transparent conductive oxides
bwww.beneq.com
/Applied Physics - Erwin Kessels
Batch ALD reactor
• Temporal ALD
• Typically 50-500 substrates in a single deposition run
• Single-side deposition can be challenging
• Applications: semiconductor (memory), displays,Applications: semiconductor (memory), displays,
solar cells, etc.
/Applied Physics - Erwin Kessels
www.asm.com www.beneq.com
Spatial ALD concept
• Precursor and reactant pulsing occur at different positions• The substrate or the “ALD deposition head” must moveThe substrate or the ALD deposition head must move• Purge areas created by inert gas barriers prevent CVD reactions
requires operation at high pressure• No gas switching or vacuum pumps no deposition on the reactor walls• No gas switching or vacuum pumps, no deposition on the reactor walls
/Applied Physics - Erwin Kessels
Spatial ALD: S2S and R2R
• Sheet-to-sheet (S2S, or wafer-to-wafer)
M i 1www.levitech.nl
Movie 1
Movie 2
• Roll-to-roll (R2R)
www.solaytec.com
Movie 2
www.lotusat.com www.beneq.comwww.tno.nlMovie 3
/Applied Physics - Erwin Kessels
Summary
1. ALD can fulfill stricter requirements on thin film growth in terms of growth control, conformality, uniformity and low temperature
2 ALD is therefore complementary to PVD and CVD techniques2. ALD is therefore complementary to PVD and CVD techniques
3. ALD relies on surface chemistry – not all materials can be prepared
4. ALD cycle yields sub-monolayer of film (typically 0.5 – 1 Å/cycle)( )
5. ALD is gaining popularity also outside semiconductor industry
6. Runner up (method): Plasma ALD
7. Runner up (application): ALD for photovoltaics
8. High-volume manufacturing equipment is available
9 Equipment for batch ALD and S2S and R2R spatial ALD launched9. Equipment for batch ALD and S2S and R2R spatial ALD launched
10. ALD has a bright future
/Applied Physics - Erwin Kessels
Further reading and downloads
Recent literature on ALD• Book on ALD, Pinna and Knez (Eds.) Wiley VHC (2011), ( ) y ( )• Kessels and Putkonen, MRS Bull. 36, 907 (2011)
Recent literature on plasma ALDp• Profijt et al., J. Vac. Sci. Technol. A 29 050801 (2011)
Recent literature on ALD for PVRecent literature on ALD for PV• Van Delft et al., Semicond. Sci. Technol. 27 074002 (2012)• Bakke et al., Nanoscale 3, 3482 (2011)
/Applied Physics - Erwin Kessels
Title
/Department of Applied Physics