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
Advanced nodes pose
challenges for patterning
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.
http://www.clker.com/cliparts/c/o/y/d/d/p/chemistry-flask-md.pnghttp://www.clker.com/cliparts/c/o/y/d/d/p/chemistry-flask-md.png
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-ons
Variety of RF pulsing technologies
Mainstream plasma technologies
Variety of CCP
Variety of ICP
ECR
DSP/RP
Add-ons
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
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 (
2)
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 Moores 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
