Lecture 9 - University of Texas at Austin€¦ · ChE 384T / 323 Atomic Resolution…atom by atom...
Transcript of Lecture 9 - University of Texas at Austin€¦ · ChE 384T / 323 Atomic Resolution…atom by atom...
ChE 384T / 323
Lecture 9Chemical Engineering for Micro/Nano Fabrication
Nanoimprint Lithography NIL
Matt Colburn Steve Johnson S.V. Sreenivasan
Eigler, et al IBM Almaden
Xe on Nickel
Ultimate limit of high resolution patterning!!
1 atom 0,438 nm
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Atomic Resolution…atom by atom
Don Eigler
IBM Almaden Research
Center
Resolution:
1 atom ~ 0.3–0.5nm
Throughput:
one atom per minute
~ 0.02
pixels/second
Great Science but
not yet practical
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Production Lithography• 193nm step and scan
exposure
• Chemically Amplified Resist
• Water immersion lithograpy
• Cost > $60 million/tool
Resolution: 40 nm /5
Throughput: 100 wafers/hr
>300 gigapixels/sec!!!
OK…Serial Processes are Simply too Slow
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Resolution vs. Throughput
1.00
10.00
100.00
1000.00
10000.00
1. 00 E- 05 1. 00 E- 03 1. 00 E- 01 1. 00 E+0 1 1. 00 E+0 3 1. 00 E+0 5 1. 00 E+0 7 1. 00 E+0 9 1. 00 E+1 1 1. 00 E+1 3
10-6 10-4 10-2 100 10 2 104 106 108 1010 1012
STM- atom manipulation
AFM (single tip with
Silicon as resist)
E-beam lithography
(inorganic resists)
Other Gaussian E-beam
lithography (high speed resists)
Gaussian E-beam
lithography
(PMMA resist)
Res
olu
tio
n (
An
gst
rom
)
Area Throughput (μm2/hr)Don Tennant: Cornell University
Shaped & cell projection E-beam lithography
Imprint
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600 AD Imprint Lithography
Tang Dynasty Templates Mesopotamian Templates
Minoan Signet Ring
From the Bronze Age
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15th Century Imprint Lithography
JOHANNES GUTENBERG
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1980’s Nanoimprint for CDs
Phillips 2P process
– UV sensitive “lacquer”
sandwiched between
mold and thin
polycarbonate substrate
– UV light shown through
substrate to cure lacquer
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90’s Soft LithographybSoft Lithography
1. PDMS template with thiol
2. Imprint stamp
3. Transfer molecules
4. Pattern TransferAnnu. Rev. Mater. Sci. 1998. 28:153–84
Younan Xia and George M. Whitesides
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90’s Thermal Imprint Lithography
Science 5 April 1996:
Imprint Lithography with 10 -Nanometer Resolution
Stephen Y. Chou, * Peter R. Krauss, Preston J. Renstrom
NIL Process
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Pattern Density Effects
Easiest… Easy… Very Difficult!
“Residual layer”
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• S-FIL fluid dispenser
• Ink jet systemPlanarization layer
SubstrateStep 1: Dispense drops
Step 2: Lower template
and fill pattern
Step 3: Polymerize S-FIL
fluid with UV exposure
Step 4: Separate template
from substrate
Template
Substrate
Substrate
Template
Step & Repeat
Substrate
Planarization layer
Planarization layer
Planarization layer
Fused silica template, coated with
release layer
2000 Step and Flash Imprint Lithography
• Template filling driven by
capillary action
• low imprint pressure and
room temperature process
Template
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“Issues” with SFIL are:
S.V. Sreenivasan
Residual Layer
• Templates
• Orientation control
• Making 1X templates
• Residual layer control
• Defects
• Template wear
• Alignment
• Throughput
• Templates
• Orientation control
• Making 1X templates
• Residual layer control
• Defects
• Template wear
• Alignment
• Throughput
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Self-Leveling Scheme using Template Flexure
Z head
Wafer
Wafer Tip/Tilt stage
Theta stage
XY stage
Template
flexureTemplate
chuck
Template
calibration stage
Template
Remote center
of rotation
TemplateTemplate-
substrate
interface
Flexure Schematic
B. J. Choi, S. Johnson, M. Colburn, S.V. Sreenivasan, C. G.
Willson, “Design of Orientation Stages for Step and Flash
Imprint Lithography,” Journal of Int. Societies for
Precision Engineering and Nanotechnology, Volume 25,
No. 3, pp. 192-199, July, 2001.
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S-FIL vs. Optical Lithography Schematic
Greatly simplified and lower cost process
Standard Optical LithographyImprint Lithography
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First Publication of SFIL
Matt Colburn, et. al
Colburn, et.al “Step and Flash Imprint Lithography: A New Approach to
High-Resolution Patterning,” Proc. SPIE 3676 379-389 (1999)
First SFIL tool
40 nm images
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SFIL tool decade later
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Residual layer needs to be thin and uniform
Residual Layer is due to the undisplaced liquid
Residual Layer Thickness Control
ThickWedged Wavy ThickWedged WavyWavy
Residual Layers
Residual Layer
Avoid: Non-uniformities
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Focus on Continuous Process Improvement
– Minimize mean and
standard deviation of
residual layer
– Key drivers: chuck
flatness, inkjet drop
volume and location
controls, evaporation.
1. 3.
4.
2.
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Residual Layer Thickness MeasurementsEarly Results
Residual layer mean
<20nm and thickness
variation to < 6 nm TIR
0
5
10
15
20
25
1 10 19 28 37 46 55 64 73 82 91 100 109 118 127 136 145 154 163 172 181 190 199 208 217
Position #
Resid
ual
Layer
Th
ickn
ess (
nm
)
Average 18.760
Std Dev 1.103
Min 16.156
Max 21.853
Range 5.696
Residual layer thickness fully populated wafer
28 nm HP
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Residual Layer Control Today• Software and hardware has been developed to correctly jet resist, and
control the spreading of the resist in a similar fashion to full fields
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SFIL Lithography2nm Replication
(Rogers et al, Illinois)
26 nm metal 1Line and 100 nm via
11nm lines and spaces 14 nm posts
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1) Why do you think 1X projection lithography
replaced contact printing in the early 80’s??
Don’t you learn from history??
2) Do you propose attempt to do lithography
without a pellicle??!!
Defects
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Template Before and After Imprints
All visible defects disappear from
the template.
Printing is the best way to clean
an SFIL template!
This is our “Pellicle”
Template prior
to imprint
Template after second
imprint
Filthy
Template
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Cohesive vs Adhesive Separation
Material with poor mechanical properties
Cohesive Failures call for stronger materials
Fouled Templates due to
Bad Materials Properties
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First Etch Barrier Formulation “E4”
Well defined,
stable structures:
Low viscosity:
1.9cPs/20CRapid cure to high
conversion:
Si-containing monomer EGDA t-BuAc Darocur 1173
O
O
Si OTMS
OTMS
OTMS
O
O
O
OH
O
O
O
O
40nm 30nm
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Role of Evaporation in Imprint Process
Thin residual layers and ease of filling require low
viscosity & small drops.
High evaporation can lead to:
– Variable mechanical properties of imprint material
– Variation in film thickness
Evaporation of an 80pL Drop of Monomer
Initial
Drop
10
seconds
20
seconds
30
seconds
40
seconds
50
seconds
70m
~ 42%
material
loss
~ 56%
material loss
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Working etch barrier formulation
O Si
O
OTMS
OTMS
OTMS
O
O
O
O
O
O
SIA0210 44%
EGDA 15%
iBA 37%
Irgacure 4%
HO
O
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0.0E+00
2.0E+06
4.0E+06
6.0E+06
8.0E+06
1.0E+07
1.2E+07
1.4E+07
1.6E+07
1.8E+07
0 5 10 15 20 25 30 35
Elongation (%)
Str
es
s (
Pa
)0.0E+00
1.0E+05
2.0E+05
3.0E+05
4.0E+05
5.0E+05
6.0E+05
7.0E+05
8.0E+05
9.0E+05
1.0E+06
0 1 2 3 4 5 6 7 8 9 10
Elongation (%)
Str
es
s (
Pa
)
Old Stuff New Stuff
Elongation at break 1-2% Elongation at break 30-35%
Tensile Modulus 80 MPa Tensile Modulus 500 MPa
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• Break stress of new stuff is 16 MPa
Many fold improvement in Mechanical Properties
0 5 10 15 20 25 30 35
5.0x106
1.0x107
1.5x107
Old Stuff
Str
ess
(P
a)
Elongation (%)
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Separation Failures
Fluorinated Self Assembly Monolayer (F-SAM)
FSi Cl
F F
FF
FF
FF
FF
FF
OH
OSi
OSi
OSi
OSi
OSi
OH OHO
OSi
OSi
OSi
OSi
OSi
O OSi
FF F
FFF
F
Si
FF F
FFF
F
Si
FF F
FFF
F
Solution?
Separation process
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Fluorosurfactants
2-(Perfluorodecyl)ethyl acrylate (R)
Methyl perfluorooctanoate (NR)
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Adhesion Test Tool
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Instron Experiment
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Bad News!
81 shots maximum
Wa
ter
co
nta
ct
an
gle
(d
eg
ree
)
The numbers of imprints
0
20
40
60
80
100
120
0 10 20 30 40 50 60 70 80 90 100
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We have a “wear” problem
Fluorinated Self Assembly Monolayer (F-SAM)
FSi Cl
F F
FF
FF
FF
FF
FF
OH
OSi
OSi
OSi
OSi
OSi
OH OHO
OSi
OSi
OSi
OSi
OSi
O OSi
FF F
FFF
F
Si
FF F
FFF
F
Si
FF F
FFF
F
Current solution & a problem
OH
OSi
OSi
OSi
OSi
OSi
OH OSi
FF F
FFF
F
Imprints
Degradation & defects !!
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Potential Solution to the “wear” problem
SiN
Si
H
SiN
Si
F F
F F
F F
F F
F F H
F
FF
F
F F
F F
F F
F F
F F
F
F
HMDSFluorinated silazane
Comparable structure to F-SAM !!!
Replenish !!!
O
OSi
OSi
OSi
OSi
OSi
O OSi
FF F
FFF
F
Si
FF F
FFF
F
Si
FF F
FFF
F
Imprints w/ F-silazaneF
Si ClF F
FF
FF
FF
FF
FF
OH
OSi
OSi
OSi
OSi
OSi
OH OHO
OSi
OSi
OSi
OSi
OSi
O OSi
FF F
FFF
F
Si
FF F
FFF
F
Si
FF F
FFF
F
OH
OSi
OSi
OSi
OSi
OSi
OH OSi
FF F
FFF
F
Imprints
F-SAM
FSi Cl
F F
FF
FF
FF
FF
FF
Degraded …
Concept
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Multiple Imprints Results
0
20
40
60
80
100
120
0 10 20 30 40 50 60 70 80 90 100
Standard fluid
+ 5 % F-silazane
81 shotshard more imprints
100 shotspossible more imprints
Wa
ter
co
nta
ct
an
gle
(d
eg
ree
)
The numbers of imprints
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10,000 non-stop Imprints for one Template
Features: Metal-1 and
Contact arrays
– 350 nm minimum CD M1
– 400 nm contacts
– 90 nm minimum CD M1
– 80 nm minimum CD M1
– 70 nm minimum CD M1
– 120 nm contacts
– 100 nm minimum CD M1
– Program defects: 100 nm
minimum CD M1
Features: Metal-1 and
Contact arrays
– 350 nm minimum CD M1
– 400 nm contacts
– 90 nm minimum CD M1
– 80 nm minimum CD M1
– 70 nm minimum CD M1
– 120 nm contacts
– 100 nm minimum CD M1
– Program defects: 100 nm
minimum CD M1
Defect Template Wafer layout
Imprinted 82,200 mm wafers with 124 fields per wafer
Wafers were imprinted with 13 mm X 13 mm mask fields
The imprints had no unprinted streets between the imprints
No process disruptions due to particles were observed
Do not know of any limitations, we could have printed more fields
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Field-To-Field Alignment
One of Eight Interferometric Moiré
Alignment Technique (i-MAT) Cameras
Imprint
Mask
Wafer
Imprint
area
Alignment Marks
One of Eight Interferometric Moiré
Alignment Technique (i-MAT) Cameras
Imprint
Mask
Wafer
Imprint
area
Alignment Marks
Moiré metrology originally developed for X-Ray litho (Smith, Moon)
Sub-nanometer resolution, inclined optics
Insensitive to film thickness variations
Alignment and scale/shape correction are performed “in-liquid” which is
typically a 15nm residual layer
43
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Overlay: Scale/Shape Correction Mechanism
SiC Chuck &
Template
Loadcell
Gimbal
Pads
44
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1) Why do you think 1X projection lithography
replaced contact printing in the early 80’s??
Don’t you learn from history??
2) Do you propose attempt to do lithography
without a pellicle??!!
Defects
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Defect Density Trend Similar to Immersion
• Data measured on imprinted wafers – includes all sources of defects
• Steady improvement in defect density –
• Rate approximately one order of magnitude per year
• very similar to immersion lithography learning curve
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The Claims of the Detractors/Competitors
The stated “facts”…..SFIL cannot:
– Control RLT
– Align
– Defectivity, etc….
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Mask Life: Wafer Fall-On Particle Trend
100
10
0.4
0.1
0.020.01
0.003
0.0005
0.0001
0.001
0.01
0.1
1
10
100
2012 2013 2014 2015 2016
Change of number of particles on wafer[pcs/Wafer]
Hard particle reduction prolongs mask life
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Gate Level: 38nm Half Pitch
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Canon, Toshiba and SK hynix going forward
with SFIL
Revolutionizing the Semiconductor
Industry - Nanoimprint Lithography
Report: Toshiba adopts imprint litho for NAND productionJune 07, 2016 // By Peter Clarke
Toshiba will adopt nanoimprint lithography (NIL) as a way of reducing the cost of production of
NAND flash memory, according to a Nikkei report. Toshiba plans to allocate part of an 860 billion
yen (about $8 billion) budget for spending on semiconductors over the next three years on
introducing NIL into flash memory production lines, the report said. Production is set to begin in
fiscal 2017 in Yokkaichi.
ChE 384T / 323
News Release
Canon provides nanoimprint lithography manufacturing
equipment to Toshiba Memory's Yokkaichi Operations
plant
TOKYO, July 20, 2017—Canon Inc. announced today that
the company has provided the FPA-1200NZ2C,
semiconductor lithography equipment that utilizes
nanoimprint lithography (NIL) technology which Canon has
been continuously developing since 2004, to leading
provider of semiconductor memory solutions Toshiba
Memory Corporation's Yokkaichi Operations plant. The
provision of this equipment represents significant progress
toward semiconductor device mass production that employs
nanoimprint technology.
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“Back end of the line” is a lot of the process
!
Transistor
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Traditional
Dual Damascene Process
Dual Damascene Process
with Imprint Litho
Dual Damascene Process
resist
etch stop
substrate
ILD
ILD
Initial stack Trench litho Trench etch
Resist ashBARC / resistVia litho
Via etch Resist Ash
Barrier
Cu metal
CMP
Initial stack
Imprint
Breakthru etch
Cure
dielectric precursor
etch stop
substrate
Barrier
Cu metal
CMP
184 steps for 8 levels of Cu72 steps for 8 levels
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Dispense SIM Material
SFIL Damascene Process (SIM)
# of process steps:
Multi-Tier Template
Position templateFlashRelease
SFIL IMPRINTING
M1
1
Deposit barrier
Deposit CVD dielectric (BD)CVD Dielectric
23
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SFIL Damascene Process
# of process steps: 0
Sacrificial Imprint Material (SIM)
4
M1
CVD Dielectric
Etch Transfer
5
Strip (SIM)
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M1
Etch Diffusion Barrier
Copper Seed
Copper Plate
SFIL Damascene Process
# of process steps: 6789
184 – 72 = 112
Saved steps ?
x 8
72
CMP
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BEOL Multilevel Imprint Cost Saving
20% overall saving at 30 wph
Cost analysis courtesy of Sergei V. Postnikov, Infineon Technologies; presented at Semicon Europa 2007, Stuttgart, Germany
0%
20%
40%
60%
80%
100%
120%
140%
wph = 5 wph = 10 wph = 20 wph = 30 wph = 40 wph = 50
V1/M2
base line
DD:
44steps
V1/M2 Dual Damascene by NIL in resist: 27 steps
rela
tiv
e c
os
t (%
)
20%
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Damascene Swords and Jewelry
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Damascene Swords and Jewelry
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Damascene Swords and Jewelry
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Chemical Mechanical Polishing
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CMP Tools
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Via Chain Test Structure
M2
V2
M1
2.5um1.5um
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Via Chain Structures
100nm vias 100nm via100nm vias
M2 by SFIL M1 by
Photolithography
Via chain
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Via chain test site
Template
now a commercial product
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Imprinting
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Pattern Transfer Demonstration
Trench
Etch
CF4/C4F8/N 2
Ash
N2/H2
Both Coral® and Black Diamond® were processed
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Wiring Level Complete
After etch After metal
After metal
If this works, it saves more than 100 unit process
steps from the manufacturing of a modern
microprocessor and provides a saving of 20-50%
(per studies by Infineon and SEMATECH)
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Wiring Level Complete
After etch After metal
After metal
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Completed Via Chains
M2
V2
M1
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Via Chain – 120 nm 1000 Contacts
Yield statistics (6 valid and identical chains
tested)– Overall yield of 1000-contact chains with via CD 120 nm
(nominal) / 115 nm (final) – 96.83%
– Individual contact yield – 99.9968%
Template CD = 120 nm
Final CD = 115 nm
0
20
40
60
80
100
0 2 4 6 8 10 12 14 16
Via Chain Resistance (Ohm per contact)C
um
ula
tive P
rob
ab
ilit
y (
%)
Chain #1
Chain #2
Chain #3
Chain #4
Chain #5
Chain #6
Cu (M2)
Coral
Cu (M1)
Ta