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Y. Zhang et. al., Applied Materials
Patterning Challenges and Opportunities:
Etch and Film
Ying Zhang, Shahid Rauf, Ajay Ahatnagar, David Chu, Amulya Athayde, and Terry Y. Lee
Applied Materials, Inc.
SEMICON, Taiwan 2016
Sept. 07-09, 2016, Taipei, Taiwan
Y. Zhang et. al., Applied Materials
Outline
• Advanced nodes pose challenges for patterning
• These challenges demand new film and etch/removal capabilities
• Atomic Level Deposition
• Atomic Level Etch and Removal
– Low electron temperature plasma etch
– Highly selective radical based removal
• Closing remarks
2
Y. Zhang et. al., Applied Materials
• Lithography Technology
– 248nm
– 193nm
– 193i
– Litho multiple exposure
– EUV
– Complementary Litho
• e.g., 193i + EUV
– Key challenge:
• Overlay
• EPE
• Materials Engineering
– Etch
– Film
– ALD
– Gapfill
– Selective removal
– ALE
– Selective deposition/growth
– Key advantage:
• Enable self-align schemes
• Atomic Level Controllability
Patterning Technology Trend
4
Lithography Technology
Materials Engineering
Y. Zhang et. al., Applied Materials
SAxP Flows
• In SAxP pitch splitting flows
– 1 litho step + many non-litho steps (film, etch, etc.)
– e.g.: SAQP:
5
Litho Etch ALD Etch ALD Etch
Y. Zhang et. al., Applied Materials
CD/CDU/LER/LWR dominated by Litho, Etch and ALD
• In SAQP, there are 8 “edges”:
– Direct edge: = f (Litho CD/CDU/LER/LWR)
– S1 edge: = f (Litho and 1st spacer CD/CDU/LER/LWR)
– S2 edge: = f (1st and 2nd spacer CD/CDU/LER/LWR)
– S1/S2 edge: = f (1st , 1st spacer and 2nd spacer CD/CDU/LER/LWR)
6
Source: Schenker, Intel SPIE 2016
To systematically reduce EPE:
• CD/CDU/LER/LWR of all edges at all steps
need to be measured to trace down root
causes
• Litho the key source of LER
• Etch/ALD the key for pitch walking
Y. Zhang et. al., Applied Materials
These challenges demand new
film and etch/removal
capabilities - ALD
Y. Zhang et. al., Applied Materials Y. Zhang et. al., Applied Materials
Conventional ALD
Conventional ALD vs. OlympiaTM Reconfigures ALD
8
A
B
Off
Off
On
On
OlympiaTM ALD What is ALD?
Divides CVD into two half-reactions
Is self-limiting, producing uniform, conformal deposition
Wafer travels continuously
Spatially separated chemistries
Chemistry-free zones isolate individual chemistries
Precursor Precursor
Wafer is stationary
Alternating chemistries
Purge separates chemistries
Primary technology used today
A B A B
A B
Y. Zhang et. al., Applied Materials Y. Zhang et. al., Applied Materials
Treatment
X
Modular Design for Atomic-Level Engineering
Precursor Precursor Precursor
20n
m Silicon Oxide
20n
m Silicon Nitride
20nm
Titanium Oxide
100nm
Aluminum
Oxide
20nm
Titanium Nitride
Versatility Broadens Spectrum of
Achievable ALD Materials without Compromising
Productivity
9
A B Thermal
B p
A Plasma
Enhanced
ALD Mode Process Sequence
Atomic-
Layer
Treatment
X B A
Conventional
ALD
OlympiaTM
ALD
Source: Applied Materials, Inc.
Y. Zhang et. al., Applied Materials
These challenges demand new
film and etch/removal
capabilities - Etch
Y. Zhang et. al., Applied Materials
Plasma etching patterning trend
• Thin Layer Etching (TLE)
• Atomic Layer Etching (ALE)
• Complex pulsing technologies
• Advanced radical etching
• Low Te plasmas
• Neutral beam
• …
11
RIE
Mainstream plasma technologies
– Variety of CCP
– Variety of ICP
– ECR
– DSP/RP
Add-on’s
– Variety of RF pulsing technologies
Mainstream plasma technologies
– Variety of CCP
– Variety of ICP
– ECR
– DSP/RP
Add-on’s
– Variety of RF pulsing technologies
Y. Zhang et. al., Applied Materials
Basic Mechanisms of Reactive Ion Etching
Ion-neutral reaction synergism
– One of the most important concepts of plasma-surface chemistry is the
synergism of ion and neutral reactions
– Three key aspects of ion bombardment:
• Stimulate surface reactions
• Stimulate desorption or clear the surface of etch-inhibiting, nonvolatile residues
• Anisotropic or directional etching
12
Coburn and Winters, J. of App. Phys. 50. 3189-3196, 1979
Ion Bombardment effects in Reactive Ion Etching
Y. Zhang et. al., Applied Materials
Low electron temperature, Te, plasmas
• Intuitively, lower Te lower Vp lower ion energy lower damage
ALE(?)
• How to control low ion energy, e.g., from <4eV to ~25eV?
13
~1-2 layers
From Oliver Joubert, CNRS-LTM
~4 layers
0 1 2 3 4 50
10
20
30
40
50
SIC
Lth
ick (
A)
Cl+ Fluence (ML)
5eV
10eV
25eV
50eV
100eV
Radical Cl + Cl+ Radical Cl + 25eV Cl+
Radical Cl + 5eV Cl+
Y. Zhang et. al., Applied Materials
Low Te Plasma Etch System • A low Te plasma is produced in the processing chamber using energetic beam
electrons in the 0.5 – 2.5 keV energy range.
• A separate inductively coupled plasma (ICP) based radical source is used in our system to provide accurate control over relative concentrations of radicals and ions
• Another important element in this plasma processing system is low frequency RF bias capability which allows control of ion energy in the 2 – 50 eV range
14
e-beam source
Radical source
Bias (wafer voltage)
x
Y. Zhang et. al., Applied Materials
Ion / Radical Composition: RF and Low Te Plasmas
• In an RF plasma (with Te = 4.0 eV), significantly more electrons can
dissociate than ionize due to lower threshold for dissociation.
• In a low Te plasma produced using energetic electrons, radical / ion
fraction is much lower.
15
1 10 100 1000 0
2
4
6
Cro
ss-s
ecti
on (
Å2)
Energy (eV)
f e (
au)
1.0
0.8
0.6
0.0
0.2
0.4
sion
sdiss
fe @ Te = 4.0 eV
fe @ Te = 0.2 eV
Ebeam
1.2 Cl2
Y. Zhang et. al., Applied Materials
Low Te Plasma can etch Si layer-layer with minimal damage
• The top surface can be more quantitatively analyzed using electron energy loss
spectroscopy (EELS).
• The thickness of the amorphous layer at the top is similar for the unprocessed sample and
the sample which has been etched in the low Te plasma only.
• When RF bias is applied to increase Ei, the amorphous layer thickness increases.
• The sample that was etched in the inductively coupled plasma without bias shows similar
damage to the 0.8 W etch case.
16
Y. Zhang et. al., Applied Materials
These challenges demand new
film and etch/removal
capabilities – Selective Removal
Y. Zhang et. al., Applied Materials Y. Zhang et. al., Applied Materials
18
What is Extreme Selectivity?
SelectraTM Removes Target Material without Damage to Others
Critical for Patterning and 3D Architectures
No Damage or
Residues Remaining
Multiple Material
Layers are Formed in
a Structure
Extreme Selectivity Enables
Removal of Only One
Material
Y. Zhang et. al., Applied Materials Y. Zhang et. al., Applied Materials
Traditional Wet Etch
• Collapse of high aspect ratio
structures
• Inability to penetrate small
dimensions
Traditional Dry Etch
• Lacks extreme selectivity
• Insufficient lateral etch
control
New Etch Methods Required to Continue Scaling
Traditional Etch Technologies Unable to Advance Moore’s Law
19
Tight Features
0
20
40
60
80
100
10 15 20 25 30
Coll
apse
Per
centa
ge
(%)
Aspect Ratio
Pattern Collapse Lateral Control
Overetch
at Top
Insufficie
nt at
Bottom
Graph Courtesy of imec
Internal
Image
Internal Image Internal Image
Incomplete
Removal
Y. Zhang et. al., Applied Materials Y. Zhang et. al., Applied Materials
• Plasma creates etchant
chemistry
• Ions are blocked, chemistry
passes through
• Damage-free, extreme
selectivity etch without
polymers
20
How Does SelectraTM Achieve Extreme Selectivity?
The SelectraTM System Creates Tailored Chemistry for Extreme Selectivity
Y. Zhang et. al., Applied Materials Y. Zhang et. al., Applied Materials
21
Extreme Selectivity Enables ≤10nm Multi-Patterning
Post-
SelectraTM SiN
Ox
Ox
9.3n
m
Internal Image
Pre-
SelectraTM
Si
SiN
Ox
Ox
9.3n
m
Internal Image
No change
in spacer
width
Y. Zhang et. al., Applied Materials Y. Zhang et. al., Applied Materials
22
Atomic-Level Precision Enables ≤10nm FinFET
SelectraTM Enables Fin Scaling and Penetration of Atomic-Level
Structures
Applied Materials Internal
Structures
0
2
4
6
8
10
Etc
h A
mo
un
t (Å
)
Silicon etch of two
atomic layers
Pre-SelectraTM Post-SelectraTM
Internal Image Internal Image
Ox
Si
Ox
Si
Si
TiN Ox
α-Si
Can access
spaces <5
silicon
atoms
across
TiN
Ox
Pre-SelectraTM Post-SelectraTM
Internal Image
Si
Internal Image
Y. Zhang et. al., Applied Materials Y. Zhang et. al., Applied Materials
23
Lateral Etch Uniformity Enables 3D NAND
SelectraTM Etch Creates Consistent Contact Resistance
Pre Etch SelectraTM Etch Traditional Etch
Y. Zhang et. al., Applied Materials
Closing Remark
• Advanced nodes pose challenges for patterning
– Patterning trend: Litho dominating Litho/Materials engineering dominating
– Recent EUV emerging will help Litho, e.g., complementary litho, but not likely change this trend
• These challenges demand new film and etch/removal capabilities
– CD/CDU/LER/LWR play increasingly critical role in scaling
– Etch/Removal and Film play increasingly critical role in EPE reduction
• More opportunities for Film and Etch/Removal but key challenges are to have atomic level precision
– Atomic Layer Deposition
– Atomic Layer Etch and Removal
• Low electron temperature plasma etch
• Highly selective radical based removal
24
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