浅川鋼児 - TOKYO TECH OCW

材料物理科学特別講義第３
Photo Lithography
東芝　研究開発センター
浅川　鋼児
2011/4/13
Copyright 2011, Toshiba Corporation.
Copyright 2011, Toshiba Corporation.
Lithography in Electronics Industries
Typical Photolithography Process
• Most of the electronic
devices are made by
lithography.
Light
Source
– Semiconductors
– Hard disk drives
Reticle
(Mask)
– Flat panel displays
Resist
– Printed Circuit Board
Wafer
1.Spincoat
東京工業大学　講義資料　110413
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東京工業大学　講義資料　110413
2.Expose
3.Develop
4
Evolution of Lithography
Lithography in Semiconductor Process
Process flow of MOS transistor
Si wafer
Form Poly Si
The International Technology Roadmap for semiconductors (ITRS)
http://www.itrs.net/
Form protective
film
Form insulate layer
1000
Deposit Si3N4
Etch Poly Si
Lithography 3
Source drain
pattern
Form metal film
Etch Si3N4
Ion implantation
Lithography 5
Wire pattern
Form gate oxide
layer
Etch metal film
3
Etch protective
film
Etch insulate layer
Lithography 1
Isolation pattern
6
5
4
Lithography 6
Bonding pad
pattern
Lithography 4
Contact pattern
Half Pitch / nm
Lithography 2
Gate pattern
Surface oxidization
Electric property
test
100
Next
???
Wavelength of
Light source
1990
2000
2010
2020
Year of Production
Famous
“Moore’s law”
An integrated circuit
for minimum component
doubles every 2 years
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Exposure wave lengths and optical materials
NA
λ
Exposure
wave length
(nm)
Shorter wavelength
g-Line (436nm)
→ i-Line (365nm)
→ KrF (248nm)
→ ArF (193nm)
→ F2 (157nm) ?
→ EUV(13.5nm)?
Mask
Projection
Lens
Light Source
(nm)
Atmosphere
13
EUV
13.5
Vacuum
Greater NA
0.24　→　0.46
→　0.63
→　0.75
→　0.85
→　0.93
→　1.20
→　1.35
High Pressure
Mercury Lamp
UV laser
Illumination optics
東京工業大学　講義資料　110413
ArF excimer
193nm
6
5
4
10
1980
5
Resolving Power ∝ k 1
Wafer
i-line
365nm
2
Photo Lithography
Projection lens
g-line
436nm
DRAM
Flash
3
Even simple
transistor requires
several PhotoExposure
Processes (PEP)
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KrF excimer
248nm
Optical System
Optical Materials
100
200
Ar2 F2
127 157
ArF
193
Absorbed by
Oxygen, Water, etc.
Catoptric System
Multilayer
Metal Film
300
KrF
248
400
XeCl
308
i
365
g
436
Normal Air
Diptric System
Fluorite
Synthetic Quartz
Optical Glass
Immersion
7
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Electron Beam Resist (Main Chain Scission)
Photoresists
KPR
m
m
Cl
n
m
n
O
COOH
PMMA
O C C
H H
Cl
O
O
OCH2CF3
CH2CH3
EBR-9
n
hν
H H
O C C
C C O
H H
C C O
H H
n
n
poly(vinyl-cinnamate) (PVCN)
ZEP520A
hν
KTFR
n
n
O
EB
cyclized rubber
N3
N3
CH3
bisazide
O
g-line and i-line
Resist
Substrate
Substrate
東京工業大学　講義資料　110413
O
O DNQ
DNQ O
SO2
DNQ
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10
Chemically Amplified Resists
Photo Resist
H+
KrF Resist
hv
ΔH
O
Reticle
PAG
n
m
n
m
Inhibitor
(Insoluble to
Developer)
COOH
hν
SO2
novolac resin
Chemical Amplification Resist
Si Wafer
N2
OH
n
CH3
Substrate
O
DNQ
OH
+
S CF3 SO3
1.Spincoat
- hν
CH3
CO2
OH
OH
OH
CH3
CH3
Acid
KrF resin
Generated
Acid from PAG
PAG (for KrF and ArF)
2. Expose
ArF Resist
O
H+
n
m
O
O
ΔH
O
m
O
COOH
n
O
COOH
O
3.Bake
Decomposed
Inhibitor
(Soluble to
Developer)
ArF resin
4. Develop
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Optical Proximity effect Correction (OPC)
日立　岡崎様資料
Images projected at the same wavelength by the same optical system
K1 : 0.8
K1 : 0.6
Design
on Mask
K1 : 0.4
K1 : 0.3
Optical
Image
hammerhead
Serif
Serif
sub resolution
pattern
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Double patterning
Immersion Lithography: Greater NA
Light
Revolution of Stepper
Projection lens
n0=1.0
resist
nP=1.5
θ
n0 =1.0
wafer
n0=1.0
resist
nR=1.7
Projection
Lens
Total
reflection
Exposure
1.0
0.95
0.85
0.75
Mask
Resist
substrate
Slim Pattern
NA = n0sinθ
= sin θ
wafer
Deposit Spacer
NA is limited to 1
Projection lens
Etch Spacer
water
resist
ni =1.4
Resolving Power ∝
NA
λ
wafer
ni =1.4
Shorter wavelength
Greater NA
g-Line (436nm)
→ i-Line (365nm)
→ KrF (248nm)
→ ArF (193nm)
→ F2 (157nm)
0.24 →　0.46
→　0.63
→　0.75
→　0.85
→　0.93
東京工業大学　講義資料　110413
nP=1.5
ni =1.4
θ
nR =1.7
Qz
Remove Resist
1.20
1.05
Water
0.95
0.85
0.75
Remove
unnecessary part
Water
Resist
NA= ni sinθ
NAND Flash Memory
Fabrication
Greater NA than 1 is realized
15
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Key to the ArF resist resin
=> To add hydrophilicity to alicyclic compounds
Dry-Etch Resistance
Acrylic polymer
with alicyclic side chain
Development of Resist
O
n
m
Fujitsu, NEC, Toshiba
Alicyclic main chain polymer
O
O
IBM, ATT, Samsung, Hundai
O
O
O
O
O
O
O
O
HO
Hydrophilicity
Acrylic polymer
with alicyclic side chain
Alicyclic main chain polymer
Easy to modify
High dry-etch resistance
Low dry-etch resistance
High price of monomers
Shelf life
Resolution
東京工業大学　講義資料　110413
Copyright 2011, Toshiba Corporation.
Developed Resist Performance
18
Molecular Resists
Lithographic Technology
Technology Node Size
m
O
O
O
COOH
ΔH
n
O
H+
O
O
Resist
m
n
High Resolution
O
O
Low Line-Edge-Roughness (LER)
+H2O
Shrinkage
O
OH
COOH
Molecular Resist
HO
10.0
High Sensitivity
LER
Polymers
High Resolution & Low LER
11.6
R
Solubility parameter
δ (cal1/2cm-3/2)
OH
OH
OH
HO
CH 2
OH
Large !
n
0.13 μmL/S
0.12 μmL/S
HO
0.11 μmL/S
Exposure Tool : Nikon NSR Stepper with NA=0.6, sigma=0.75, 2 mJ/cm2
東京工業大学　講義資料　110413
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Calixarene
Dendrimer
OH
Catechol Derivative
東京工業大学　講義資料　110413
Mw = ca. 20000
Main Factor: Molecular Size
20
Molecular Resists at Toshiba
Negative-Working Molecular Resist Derived from Truxene
Amorphous Truxene
OH
Cross-Linker
OH
Nanopatterning with Microdomains of
Block Copolymers using Reactive-Ion
Etching Selectivity
O O
N
N N
O N N N O
O
O
HO
HO
OH
OH
THBTX : MAT = 75 : 25
Higher Etching Durability Compared with Polymer
Fabrication of hp 20 nm-Scale L&S Pattern
100 nm
東京工業大学　講義資料　110413
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Copyright 2011, Toshiba Corporation.
Next Generation Lithography (NGL)
Hierarchical structures of block copolymers
30oX
Mold
Resist
Substrate
X X X X X X X X X
(CH2)n
2-3nm
Press mold
X
SH
SH SH SH SH SH SH SH SH SH SH
Gold
Anodic Porous Alumina
Remove mold
Domains
Self-Assembled Monolayer
(SAM)
(a).Micro-phase
separated structure
Etching
Ink
Nano Beads
Writing
direction
Substrate
Block Polymer
東京工業大学　講義資料　110413
A segment
Print
B segment
CH3
n
Molecular
Transport
n
n
n
n
O
PB
N
Water
Meniscus
Substrate
Natural Lithography
(b).Block copolymer
Substrate
AFM Tip
Etching
Chemical bond
PDMS
Nanoimprint
n
PS
Release
P2VP
OH
PHS
O
PEO
O
CH3
CH3
Si
PI
PMMA
n
O
n
CH3 PDMS
Soft Lithography
(c).Typical segments consisting block copolymers
Dip Pen Lithography
23
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Micro-Phase Separated Structures of
Block-copolymer
Spherical
Cylindrical
Bicontinuos
Chemical bond
Lamella
Remove A polymer
B
A
Molecular Weight
A polymer
Change in Size
B polymer
Micro-Phase Separation of Block Copolymer
Repulsion
Annealing
Microphase separation
Composition
Change in Structure
Self-assembled nano-structures
K. Asakawa, T. Hiraoka, Jpn. J. Appl. Phys. vol.41, 6112 (2002).
東京工業大学　講義資料　110413
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First Block Copolymer Lithography
Princeton University
26
Method to remove one phase of block copolymer
• C. Harrison at Chaikin’s Lab
(Physics) and M. Park at
Register’s Lab (Chem. Eng.)
started experiments.
Substrate
High Energy Beam
Prof. Richard A. Register
Prof. Paul M. Chaikin
Me
O3
Me
O3
Metalized
O3
Ozonized
Scission & Develop
M. Park, C. Harrison, P. M. Chaikin, R. A. Register,
and D. H. Adamson, Science vol. 276, 1401 (1997).
PB,PI (Os)
PS (Ru)
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Etching
PB,PI
東京工業大学　講義資料　110413
PMMA,PαS
Selective RIE
PS-PMMA
PDMS-PS (O2)
28
Relationship between N/(Nc-No) and Dry-etch Rates etched by CF4.
6
n
• Fabrication using Block-Copolymer as a Mask
Gas: CF 4
Pressure: 0.01 torr
Output: 150W
PHS
①Coat
Etch Rate / nm s
-1
5
4
OH
n
PtBMA
PS
2
n
PVN
1
②Generate Phase
Separated Structure
PMMA
CH 3
3
Nano-Pattering Technique
③Etch Phase
Separated Film
& Substrate
④Remove
Polymer Film
by Ashing
CH 3
n
n
C=O
C=O
O
O
C(CH 3 ) 3
CH 3
Only RIE
PB
n
0
0
1
2
3
N/(N C -N O )
4
5
6
The polymers containing more carbon have strong dry-etch resistance,
and the polymers containing more oxygen are etched easily.
K. Asakawa, T. Hiraoka, Jpn. J. Appl. Phys. vol.41, 6112 (2002).
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Micro-Phase Separated Patterns of Block-Copolymer
and Silicon surface after CF4 etching
Ozone, Osmium
Metal, etc.
K. Asakawa, T. Hiraoka, Jpn. J. Appl. Phys. vol.41, 6112 (2002).
東京工業大学　講義資料　110413
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Summary of block copolymer lithography
• The nano-meter scale dot pattern can be obtained by
self-assembled block copolymer films.
• This method does not require complicated materials
and processes and can be used as etching masks for a
lot of purposes in the industries.
K. Asakawa, T. Hiraoka, Jpn. J. Appl. Phys. vol.41, 6112 (2002).
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Applications for Electronic Devices
Transparent
Conductive Metal
LED
Transmittance　60%
@opening　27%
Metal wires
for Memories
500nm
500nm
(a)
33 nm pitch (16.5nmL/S)
metal nano-wires
Al nano-mesh
TCO
Al thin film
nano-meshed aluminum on 4-inch wafer
(b)
P. Vincent et. al., Appl. Phys. Lett.
vol. 88, 211114 (2006)
Nakanishi et. al. , Appl. Phys. Exp. vol. 4 025201 (2011).
K. Asakawa et. al, Appl. Opt., vol. 44, 7475 (2005)
Antireflective
structure
Hard Disk Media
Nano-Patterned Magnetic Media for Hard Disk Drive
(Application of Block Copolymer Lithography)
OLED
P: 700nm
H: 440nm
2.5-inch disk
1.0
4000
3500
0.8
3000
Reflectivity
100nm
発光強度
0.6
0.4
Magnetic
particles
2500
2000
1500
1000
0.2
500
0
0.0
380
450
430
K. Naito et. al. IEEE Tran. Magn, vol. 38, 1949 (2002)
480
530
580
630
680
500
730
550
600
650
波長 / nm
WaveLength/nm
Nakanishi et. al. , Jpn. J. Appl. Phys, vol. 40, 075001 (2011).
Nakanishi et. al. , Appl. Opt., vol. 48, 5889 (2009)
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Trend of HDD
Copyright 2011, Toshiba Corporation.
Patterned Media for HDD
Conventional Media
Heterogeneous in Size and Shape
Perpendicular
recording
Density / Gb inch
-2
1000
GMR-head
100
Advanced
longitudinal media
10
Magnetic
particle
1bit
MR-head
1
100nm
0.1
1985
Surface Structures of
Magnetic Film
Patterned　media
1990
1995
2000
2005
2010
2015
Next generation media
Homogenous in Size and Shape
Year of Production
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Fabrication Process of Patterned Media
Concept of Artificially Assisted
Self-Assembly method (Guided self-assembly)
Phase-separation takes place in the grooves to produce
aligned dot patterns.
on a flat surface
Anneal for
Phase Separation
Coat Block-copolymer
in 200nm width grooves
Etch
Fill
Block-Copolymer SOG (Spin on Glass)
Into polymer dots
2μm
Etch
magnetic Layer
Remove
Polymer
K. Asakawa, T. Hiraoka, H. Hieda, M. Sakurai, Y. Kamata, K. Naito, J. Photopolym. Sci. Technol. vol. 15, 465 (2002).
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Patterned Media on 2.5-inch Disk
東京工業大学　講義資料　110413
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Perpendicular M-H Loops of Raw Continuous film (CoCrPt)
M / emu
0.005
Before Etch
Magnetic Particles
Etch 3min
Etch 6min
CoPt
2.5-inch Disk
Ti
-10
0
10
H / kOe
[Co74Pt26(40 nm) /Ti(5nm)]
100nm -0.05
A coercive force (2950 Oe) and squareness ratio (0.70) of the
patterned film increased compared to those of the continuous film.
K. Asakawa, T. Hiraoka, H. Hieda, M. Sakurai, Y. Kamata, K. Naito, J. Photopolym. Sci. Technol. vol. 15, 465 (2002).
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Katsuyuki Naito et. al. IEEE Tran. Magn, vol. 38, 1949-1951 (2002)
東京工業大学　講義資料　110413
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MFM Images of Patterned Media
Circumferentially aligned FePt dots
AFM　image of 30-nm-pitch dot pattern
Photo image of 2.5” disk
500nm
After　AC erase
After DC erase
MFM images of Co74Cr6Pt20dots
¾Circumferentially aligned FePt dots were uniformly fabricated
on a whole HDD substrate
Katsuyuki Naito et. al. IEEE Tran. Magn, vol. 38, 1949-1951 (2002)
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H. Hieda, Y. Yanagita, A. Kikitsu, T. Maeda, K. Naito, J. Photopolym. Sci. Technol., 19, 245 (2006).
東京工業大学　講義資料　110413
Summary of Bit Patterned Magnetic Media
• Using self-assembled block-copolymer and
nanoimprint lithography, a circumferential magnetic
patterned media on a 2.5-inch diameter glass plate was
fabricated.
• A coercive force and squareness ratio of the patterned
film increased compared to those of the continuous
film.
• 1Tbpsi magnetic dots were fabricated by selfassembled block copolymer.
• Distribution of magnetic dots was narroed by
optimizing the guide for aligning.
• Nanoimprint mold was fabricated for high volume
manufacturing.
東京工業大学　講義資料　110413
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High Luminescent Light-Emitting
Diode with Columnar Structure on
the Surface
Copyright 2011, Toshiba Corporation.
42
Efficiency of Commercially Available Lamp
Current Issues of LED
Low Light
Extraction
Upper Electrode
140
Surface
Efficiency / lm/W
Below Total
Above Total
Reflection Angle Reflection Angle
Sodium Lamp
120
Current Diffusion
Layer
100
Air n = 1
Active Layer
80
Fluorescent Lamp
60
1965
1934
LED substrate
n = 3.2(Red)
n = 2.5(Blue)
LED
Reflector
40
1959
20
Tungsten-Halogen Lamp
Most of light cannot go
out of LED…
Incandescent Lamp
1879
0
1920
1996
1930
1940
1950
1960
1970
1980
1990
OLED
2000
2010
Year
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Scale Range of Columnar Structures vs. Light
46
How to Extract More Light?
- Antireflection structure and Diffraction structure
Geometric Optics
Wave Optics
東京工業大学　講義資料　110413
Below Total
Reflection Angle
Effect is enhanced
by reflector
Above Total
Reflection Angle
Air n = 1
LED substrate
n = 3.2
Efficiency
Diffraction
~X2
(2) Graded Index
Light Ray
Reflection
~X1.5
Anti Reflection
~X1.2
-1st Order Light
Visible
Light
100nm
(3) Grating
-1st Order Light
1μm
Self-Assembling
Wave Length
of Light
(4) This Study
Nanoimprint
Photo Lithography
東京工業大学　講義資料　110413
(1) Flat Surface
47
東京工業大学　講義資料　110413
Most of light
cannot go out
of LED…
If there are nanostructures on the LED
surface, more light can
be extracted.
Structure size is
smaller than
wavelength
48
Fabrication process
(1) Spincoat SOG
Nano-Patterned Surface on AlGaAs-LED
(2) Spincoat
block copolymer
(3) Microphase-separation
by annealing
Block copolymers
(PS-PMMA)
PS
GaP
SEM image of LED surface
Emitted LED tips
500 nm
Brighter!
SOG
(Organic silica)
(4) Remove PMMA
by O2 RIE
Remaining
PS dots
(5) Dry-etch SOG
by CF4 (6) Dry-etch LED substrate
by Cl-based gases
Flat surface Patterned surface
Diameter 100 nm,
Period 150 to 200nm,
Height 450 to 500 nm.
1.8 times Brighter than conventional LED.
K. Asakawa, A. Fujimoto, Appl. Opt., vol. 44, 7475 (2005)
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A. Fujimoto, K. Asakawa, Toshiba Review, vol.60, no.10 pp32 (2005)
東京工業大学　講義資料　110413
Summary of high luminescent LED
Princeton University
• Nano-structured surfaces were fabricated by
self-assembled block copolymers.
• The external efficiency of the fabricated
surface on the GaP was improved 2.6 times
compared with the flat one.
• Brightness of AlGaAs LED having the new
extracted structure increased 1.8 times
compared with the flat surface.
東京工業大学　講義資料　110413
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Aligning Block Copolymers
51
Copyright 2011, Toshiba Corporation.
Microphase separation of block copolymers
Grapho-Epitaxy and Chemical Registration
Chemical bond
PS
PHMA
(Polystyrene)
(Poly-hexylmethacrylate)
Top Down Method
PS-PHMA (1:3) forms
cylindrical domains
Repulsion
Heat Annealing
Bottom Up Method
Microphase separation
Self-assembled
nano-structures
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Chemical Registration of Block Copolymer Thin Films
Grapho-Epitaxy
Form Groove
Coat Block-copolymer
60+ nm
1 row
150nm
2 rows
200nm
3 rows
Anneal for
Phase Separation
250nm
4 rows
Nealey’ Group, The University of Wisconsin
400nm
6 rows
Just
width
1 row
Groove width
Row width
ratio
1
2 rows 3 rows
2
1 x 2 pattern
東京工業大学　講義資料　110413
3
4 rows
4
6 rows
5
6
S. O. Kim, H. H. Solak, M. P. Stoykovich, N. J. Ferrier, J. J. de Pablo, P. F. Nealey, Nature 2003, 424, 411.
4-5 zigzag pattern
55
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Prof. Paul F. Nealey
Chemical and Biological Engineering
Fig. 1. Process to create lithographically defined chemically prepatterned surfaces and subsequent directed assembly. (A)
Electron-beam lithography patterns at Ls = L0 (left) and Ls = 2L0 (right). (B) Chemical contrast on the substrate after O2
plasma exposure on the e-beam–defined spots above. (C) Block copolymer thin film. (D) Guided self-assembly in
registration with the underlying chemical pattern.
D. S. Kercher, T. R. Albrecht, J. J. de Pablo, P. F. Nealey, Science 936 vol. 321 (2008)
D. S. Kercher, T. R. Albrecht, J. J. de Pablo, P. F. Nealey, Science 936 vol. 321 (2008)
57
ITRS2009
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Conclusion
Top-down lithography and bottom-up self-assembling
Low <= Cost of Fabrication => High
Directed self-assembly (DSA) is still on the list.
Photolithography
EUV
13.5nm
New Device
Creation
F2
157nm
ArF
193nm
i-line
365nm
KrF
248nm
Low cost
Ultra fine
High Accuracy
Self-Assembling
100
Low <= Alignment Accuracy => High
東京工業大学　講義資料　110413
10
Target Resolution /nm
東京工業大学　講義資料　110413
59
東京工業大学　講義資料　110413
60