resolution, lwr, and sensitivity improvement on polymer...
TRANSCRIPT
Page 1 October 19, 2009
Resolution, LWR, and sensitivity improvement on polymer-based
resist materials
Shinji Tarutani, Hideaki Tsubaki, Tooru TsuchihashiFUJIFILM CorporationElectronic Materials Research Laboratories
Page 2 October 19, 2009
Outline
1. Challenges to EUV resist materials
2. Design policy to overcome RLS trade-offs
3. Technologies to improve RLS
4. Summary
Page 3 October 19, 2009
1. Challenges to EUV resist materials
LWR
Resolution
Eopt
Simultaneous improvement of resolution, LWR and sensitivity
Critical issues of EUV resist
Will CAR indeed be able to meet the requirements for 22 nm HP spec and beyond?
What technologies would be needed to do them?
Page 4 October 19, 2009
1. Challenges to EUV resist materialsLithographic performance of a CAR
• Basically 25nm HP resolution, 5nm LWR and 12mJ/cm2 sensitivity were demonstrated. These are still far behind the target.
ResolutionResolution LWRLWR SensitivitySensitivity
22 (22 (nm)nm) < 10 (< 10 (mJmJ/cm/cm2 2 ))12.2 (12.2 (mJmJ/cm/cm2 2 ))Performances Performances 25 (25 (nm, partially)nm, partially) 5.0 (5.0 (nm)nm)
ITRS HVM SpecsITRS HVM Specs < 2.2 (< 2.2 (nm)nm)
Page 5 October 19, 2009
2. Design policy to overcome RLS trade-offs
The first : Dependence of LWR and sensitivity on quencher amount
LWR is improved by increasing the loading amount of quencher with losing sensitivity. How would LWR be improved without losing sensitivity?
⇒ Large amount of generated acid⇒ Acid (de-protection) contrast enhancement
Two important results leading to our design policy
Ecd=30nm vs LWR @ L30P60
123456789
10
0 10 20 30 40 50 60
EUV_Ecd=30nm Sensitivity [mJ/cm2]
EU
V_L
WR
@ L
30P
60 [n
m]
Increasing loading amount of quencher
(SPIE 2007)
MET@ALS
EUV exposure
2
4
6
8
10
LWR
, nm
Dose to size, mJ/cm2
0 10 20 30 40 50 60
Page 6 October 19, 2009
2. Design policy to overcome RLS trade-offs
EUV exposure
MS-13 Microstepper (NA=0.3), FT=125 nm, PB = 120 oC/ 90 sec, PEB = 110 oC/90sec, Dev.= TMAH 2.38% 60 sec,
80 nm 70 nm 60 nm 50 nm 45 nm
HighMw
40 nm
Mid.Mw
LowMw
Resolution is improved by lowering the Mw of polymer.
⇒ Minimization of dissolution unit size
The second : Dependence of resolution on polymer MWTwo important results leading to our design policy
Page 7 October 19, 2009
2. Design policy to overcome RLS trade-offs
LWR
Resolution
Eopt
Simultaneous improvement of resolution, LWR and sensitivity
Design policy to overcome those trade-offs
Large amount of generated acid
Acid (de-protection) contrast enhancement
Minimization of dissolution unit size
Critical issues of EUV resist
Page 8 October 19, 2009
2. Design policy to overcome RLS trade-offs
Enhancement of Aerial Image Contrast
e-
EUV
Resist
Acid
e- trapAcid quencher
e-
e-
e-
〔Deprotection〕
x
①
②
③④
Enhance electron generation①
Reduce electron diffusion②
Enhance acid generation③
Reduce acid diffusion④
Increase ionization efficiency
Increase ionization points
Increase EUV absorption
Decrease free vol. of matrix
PAG bounded matrix
Increase acid gen. efficiency
Increase PAG anion size
Increase electron trap density
Increase electron trap ability
Photo decompose quencher
Increase quenching ability
Page 9 October 19, 2009
3. Technologies to improve RLSEx. 1 ; Increase of electron trapping density
0
2
4
6
8
10
0 5 10 15 20
Dose to size (μC/cm2)
Rel
ativ
e am
ine
conc
entra
tion
PAG 0.54XPAG 1XPAG 2XPAG 3XPAG 6X
Increase of PAG loadingIncrease of PAG loading
==
Correlates to [Acid] Correlates to [Acid] generated by exposuregenerated by exposure
E-beam exposure
Acid generation yield increased by increasing PAG loading, Acid generation yield increased by increasing PAG loading, but saturated at high PAG loadings.but saturated at high PAG loadings.
C. R. Szmanda, et al,, J. Vac. Sci. Technol. B 17, 3356 (1999).
[PAG]: Low[Polymer]: High
[PAG]: High[Polymer]: Low
Page 10 October 19, 2009
3. Technologies to improve RLSEx. 2 ; Increase of electron trapping ability
Polymer
①②Secondary
electron generation
Electron trap and acid generation
PAGCH2 CH
OH
S O3S-Ar
CH2 CH
OH S
O3S-ArAr-SO3H
+ e
EUV
R
R
Polymer ionization Electron trapping ability- PAG loading- PAG electron affinity
Strategy to individually enhance (1) polymer ionization frequencStrategy to individually enhance (1) polymer ionization frequency y and (2) electron trapping ability of PAG should be required.and (2) electron trapping ability of PAG should be required.
R
Proposed mechanism
Page 11 October 19, 2009
3. Technologies to improve RLSEx. 2 ; Increase of electron trapping ability
Higher reduction potential (V) of PAG gave larger amount of generated acid.
S
Z
X
Y0.0
0.5
1.0
1.5
2.0
2.5
-2 -1.5 -1 -0.5 0
reduction potential (V)
genera
ted
acid
(re
l.)
Y:non-bond
Y:single bond
Y:SO2
Electron trapping ability of PAGs
Page 12 October 19, 2009
3. Technologies to improve RLS
Energy diagram for an electron in resist matrix
PAG-1 PAG-2
e-
Electron
HOMO
LUMO
Electron trapping ability
PAG-1 PAG-2<
Why the amount of generated acid was increased as reduction potential of PAG becomes higher?
Ex. 2 ; Increase of electron trapping ability
Reductionpotential
-(Minus)
+(Plus)
Page 13 October 19, 2009
3. Technologies to improve RLSEx. 3 ; Increase of ionization efficiency
0
0.5
1
1.5
2
2.5
0 2 4 6 8 10Normalized Protection ratio
Rel
ativ
e ac
id g
ener
atio
n yi
eld
PHSPolymer-APolymer-BPolymer-CPolymer-E
The highest acid generation yield was obtained with polymerThe highest acid generation yield was obtained with polymer--E.E.
Ionization potential,Molecular size, Hydrophilicity,Protection ratioE-beam exposure
x 1.5~2.0 higher
OH2+OH
OH
O
+
S+CF3S
O
-OO
OH
e-
EUV light
CF3SO
HOO
BELT
Thermalization/ e- stabilization
R
Ionization
X-RHX-R
Normalized protection ratio0
1
2
Rel
ativ
e ac
id g
ener
atio
n yi
eld
EUV light
BELT
Page 14 October 19, 2009
3. Technologies to improve RLSEx. 3 ; Increase of ionization efficiency
Polymer-E Polymer-A
Data courtesy of SeleteSFET, 0.3NA, Annular (0.3 / 0.7)Resist film thickness: 60 nm
Dose to size: 9.1 mJ/cm2
LWR(short range): 6.3 nmResolution: 28 nm
32 nm L/S
Dose to size: 10.6 mJ/cm2
LWR(short range): 5.9 nmResolution: 25 nm
PolymerPolymer--E improved sensitivity (14%), E improved sensitivity (14%), but this was rather smaller than the increase in acid yield (50~but this was rather smaller than the increase in acid yield (50~100%). 100%).
14 % improvement
Page 15 October 19, 2009
3. Technologies to improve RLS
0
0.2
0.4
0.6
0.8
1
1.2
0.1 1 10 100
LD[nm]
∝EL/N
ils
HP=32nm HP=25nm HP=15nm
0.01
0.1
1
10
100
0.1 1 10 100
LD[nm]
∝LW
R*N
ils
HP=30nm HP=20nm HP=15nm
dhDoseLWRLWR dosecorr •
∗=ν_
diff
Ddosecorr MTFNILS
LLWR
•
⎟⎠⎞⎜
⎝⎛
∝
32
_
1
Optimal diffusion length moving toward shorter as narrowing pitcOptimal diffusion length moving toward shorter as narrowing pitch. h.
D. Van Steenwinckel, et al, Proc. SPIE, 5753, 269 (2005). , D. Van Steenwinckel, et al, J. Vac. Sci. Technol. B, 24, 316 (2006).
MTFdiff: Modulation transfer function due to diffusionLd: Diffusion length of acid, p: pitch, d: Resist thickness
Ex. 4 ; Increase of PAG anion size
0.1 1 10 100Ld, nm
0.01
0.1
1
10
100
∝LW
R*N
ILS
0.1 1 10 100Ld, nm
∝E
L/N
ILS
00.2
0.4
0.6
0.8
1.0
1.2
32nmHP25nm
15nm
32nmHP
15nm
Page 16 October 19, 2009
3. Technologies to improve RLSEx. 4 ; Increase of PAG anion size
R
S+R-SO3
-
R
R
PAG-RSize: very small
PAG-BSize: middle
PAG-CSize: large
PAG-ASize: small
X =
Diffusion length of acid was widely controllable by changing Diffusion length of acid was widely controllable by changing PAG anion structures.PAG anion structures.
D: 79.8 nm2/secLd: 1.07 x 103 nm (90sec)
D: 13.0 nm2/secLd: 1.74 x 102 nm (90sec)
D: 3.44 nm2/secLd: 46.2 nm (90sec)
D: 1.01 nm2/secLd: 13.5 nm (90sec)
X-Y-
PAG-RVery small
PAG-ASmall
PAG-BMiddle
PAG-CLarge
Page 17 October 19, 2009
3. Technologies to improve RLSEx. 4 ; Increase of PAG anion size
PAG-R PAG-B PAG-CPAG-A
EL was increased using EL was increased using PAGsPAGs with low diffusion length.with low diffusion length.
E-beam exposure
15 20 25 300
10
20
30
40
Dose to size, μC/cm2, 100 nm L/S
EL,
%, 1
00 n
m L
/S
PAG-R
PAG-A
PAG-B
PAG-C
10E0 10E1 10E2 10E3 10E4Ld, nm, at 90 sec
0
10
20
30
40
EL,
%, 1
00 n
m L
/SPAG-R
PAG-A
PAG-BPAG-C
Page 18 October 19, 2009
3. Technologies to improve RLSEx. 4 ; Increase of PAG anion size
EL, resolution, and LER were improved by using PAGEL, resolution, and LER were improved by using PAG--C.C.ZZ--factor was also improved in the range from 9 % to 51 %.factor was also improved in the range from 9 % to 51 %.
*1 At 32 nm hp, after LBNL dose calibration. *2 Average of 38 nm hp to 30 nm hp. *3 Obtained using below eq.
LBNL MET, 0.3NA, 450 Rot Dipole, σradius0.1 / σoffset0.57Resist film thickness: 50 nm
Z-factor = (Resolution)3 x (LER)2 x (Sensitivity) T. Wallow, et al., Proc. SPIE 6921, 69211F (2008).
Resist Polymer PAG EL (%) Resolution (nm)Sensitivity*1 (mJ/cm2)LER*2 (nm) Z-factor*3
Resist-A Polymer-A PAG-B 17.9 30 10.1 5.2 5.04E-08Resist-B Polymer-A PAG-C 20.8 22 15 3.9 2.48E-08Resist-C Polymer-B PAG-B 13.5 28 10.6 4.2 4.03E-08Resist-D Polymer-B PAG-C 12.3 24 10.4 3.7 2.16E-08Resist-E Polymer-C PAG-B 14.2 28 7.5 5 4.28E-08Resist-F Polymer-C PAG-C 18.1 24 11.3 4.8 3.89E-08
Data courtesy of SEMATEC
Page 19 October 19, 2009
3. Technologies to improve RLSEx. 4 ; Increase of PAG anion size
24nm HP30nm HP 26nm HP28nm HPResist-A, PAG-B
20nm HP22nm HP
Resist-B, PAG-C
Resist-C, PAG-B
Resist-D, PAG-C
Data courtesy of SEMATEC
Page 20 October 19, 2009
3. Technologies to improve RLSEx. 4 ; Increase of PAG anion size
Relation between LER and resolution was improved Relation between LER and resolution was improved by suppressing acid diffusion. by suppressing acid diffusion.
PAG-BPAG-C
TargetTarget
-Y-
-Y-
Further improvement ?Further improvement ?
EUV exposure
0 10 20 30 400
1
2
3
4
5
6LE
R, n
m
1:1 hp resolution, nm
Page 21 October 19, 2009
3. Technologies to improve RLS
TTechnologies to overcome shotechnologies to overcome shot--noise statistics are required !noise statistics are required !
0
1
2
3
4
5
6
0 5 10 15 20
Sensitivity (mJ/cm2)
LER
(nm
)
PAG-B
PAG-C
0
5
10
15
20
25
30
35
0 5 10 15 20
Sensitivity (mJ/cm2)1:
1 hp
Res
olut
ion
(nm
)
PAG-BPAG-C
Clear tradeoff relationships were observed between sensitivity Clear tradeoff relationships were observed between sensitivity and LER, and sensitivity and resolution at hp 3x nm patterning. and LER, and sensitivity and resolution at hp 3x nm patterning.
TargetTargetTargetTarget
1:1
hp re
solu
tion,
nm
0
10
20
30
0 5 10 15 20Dose to size, mJ/cm2
0 5 10 15 20Dose to size, mJ/cm2
0
1
2
3
4
5
6
LER
, nm
Page 22 October 19, 2009
3. Technologies to improve RLSEx. 4 ; Polymer bounded PAG (ultimate short diffusion length)
(50 keV point beam writing, 25 nm L/S)
Control, Polymer - PAG blend type
40 μC/cm238 μC/cm236 μC/cm234 μC/cm232 μC/cm230 μC/cm2
80 μC/cm272 μC/cm264 μC/cm256 μC/cm248 μC/cm240 μC/cm2
110 deg PEB
130 deg PEB
36 μC/cm2 76 μC/cm268 μC/cm260 μC/cm252 μC/cm244 μC/cm2
Polymer bounded PAG
Page 23 October 19, 2009
3. Technologies to improve RLSEx. 4 ; Polymer bounded PAG (ultimate short diffusion length)
(50 keV point beam writing, 30 nm L/S)
Polymer bounded PAG
66.7 μC/cm2
LWR = 2.8 nm30.0 μC/cm2
LWR = 5.4 nm
Control, Polymer - PAG blend type
Page 24 October 19, 2009
3. Technologies to improve RLS
0
1
2
3
4
5
6
0 10 20 30 40 50 60
Dose (mJ/cm2)
LW
R (
nm
)
(1) Base
(2) Photo decomporsable base
0
1
2
3
4
5
6
0 10 20 30 40 50 60
Dose (mJ/cm2)
LW
R (
nm
)
(1) Base
(2) Photo decomporsable base
Photo decomposable quencher could improve the relationship between LWR and sensitivity.
MET@ALS
Ex. 5 ; Effect of photo decomposable quencher
Acid image
[H+](x,z)
Exposed UnexposedInitial acid image
Base[B](x,z)
Acid image
[H+](x,z)
Exposed Unexposed
Photodecomposable
base[B](x,z)
Initial acid image
(1)
(2)0
1
2
3
4
5
6
LWR
, nm
0Dose to size, mJ/cm2
10 20 30 40 50 60
Page 25 October 19, 2009
3. Technologies to improve RLS
Minimization of dissolution unit size
AcidDiffusion Minimization of
molecular size Reduction ofmolecular coagulation
Ex. 6 ; Reduction of polymer molecular weight
Page 26 October 19, 2009
3. Technologies to improve RLSEx. 6 ; Reduction of polymer molecular weight
LWR improvement by reducing unit sizeLWR improvement by reducing unit size
OH
G. P. Patsis et al., Microelectronic Engineering 75 (2004) 297.
OR OR
RO RO OR OR
Hirayama et al., EUVL symposium 2008.
Approx. 2 nmApprox. 2 nm
Both low Mw polymers and molecular resists Both low Mw polymers and molecular resists can reduce their unit size for LWR reduction.can reduce their unit size for LWR reduction.
a) Polymer resist5
Gyr
atio
n ra
dius
, nm
4
3
2
1
0
Number of polymerized unit0 20 40 60 80 100
b) Molecular resist
Page 27 October 19, 2009
3. Technologies to improve RLSEx. 6 ; Reduction of polymer molecular weight
Reduce polymer Mw to improve LWR Reduce polymer Mw to improve LWR
We have designed four resists to clarify We have designed four resists to clarify if low Mw polymers demonstrate low LWR and improved RLS tradeoffif low Mw polymers demonstrate low LWR and improved RLS tradeoffs.s.
OH O O
Low postLow post--exposure baking temperature and exposure baking temperature and PAG with a bulky anion to suppress acid blurPAG with a bulky anion to suppress acid blur
Drawback: Low Tg?
AcidDiffusion
Y- Y-
Page 28 October 19, 2009
3. Technologies to improve RLSEx. 6 ; Reduction of polymer molecular weight
Lowering of polymer Mw caused a large drop in film Lowering of polymer Mw caused a large drop in film TgTg, , --8080℃℃ ! !
100
110
120130
140
150
160170
180
190
200
High Mw Mid. Mw Low Mw Low Mw + PAG-B
Tg o
f res
ist f
ilm (
゜C
)
- 80 ℃
High Mid. Low Low+ bulky PAG
- 35 ℃
Res
ist f
ilm T
g, o C
1000
150
200
100
110
120130
140
150
160170
180
190
200
High Mw Mid. Mw Low Mw Low Mw + PAG-B
Tg o
f res
ist f
ilm (
゜C
)
- 80 ℃
High Mid. Low Low+ bulky PAG
- 35 ℃
Res
ist f
ilm T
g, o C
1000
150
200
Page 29 October 19, 2009
3. Technologies to improve RLSEx. 6 ; Reduction of polymer molecular weight
Polymer Mw High Middle Low
hp 25nm
hp 32nmTop down
Esize [mJ/cm2]EL [%]LWR [nm]
10.6712.3%10.48
10.2413.8%
7.25
11.0914.5%
7.53
11.2916.8%
8.48
hp 32nmCross section
PAG (Acid)
Resolution limit hp 32nm hp 25nm hp 25 nm
Y- Y-
Res., LWR and EL were changed depending on polymer Mw and PAG. Res., LWR and EL were changed depending on polymer Mw and PAG.
PEBPEB9090℃℃ / 90/ 90secsec(std. 110(std. 110℃℃))
Page 30 October 19, 2009
3. Technologies to improve RLSEx. 6 ; Reduction of polymer molecular weight
0.01
0.1
1 10
35 35 hp 32 hp 30hp 28hp 26hp hp 32 hp 30hp 28hp 26hp
High MwHigh Mw
Mid. MwMid. Mw
Low MwLow Mw
Low Mw Low Mw + bulky PAG+ bulky PAG
High MwHigh Mw
Mid. MwMid. Mw
Low MwLow Mw
High dissolution contrast makes low Mw polymer high resolution. High dissolution contrast makes low Mw polymer high resolution.
Dis
solu
tion
rate
(nm
/sec
)
0.01
Dose, (μC/cm2, 50 eV E-beam)1 10 100
0.1
1
10
100
1000
Page 31 October 19, 2009
3. Technologies to improve RLS
45 hp32 hp
Low Mw polymer did not reduce LWR Low Mw polymer did not reduce LWR
X-sectionsat 32 nm hp
LWR
(nm
)
Molecular weight of polymerHigh
6
5
4
3
2
1
0Middle Low Low
(Bulky PAG)
Ex. 6 ; Reduction of polymer molecular weight
Page 32 October 19, 2009
3. Technologies to improve RLSEx. 6 ; Reduction of polymer molecular weight
0
2
4
6
8
10
12
0 10 20 30
EL of hp 32 nm (%)
Shor
t-ran
ge L
WR
(nm
)0
2
4
6
8
10
12
0 10 20 30
EL of hp 45 nm (%)
Shor
t-ran
ge L
WR
(nm
)
Lower EL, which indicates higher acid diffusion, caused lower LWLower EL, which indicates higher acid diffusion, caused lower LWR, R, indicating EL (resolution) indicating EL (resolution) -- LWR tradeoff. LWR tradeoff.
45 nm hp
High MwHigh Mw Mid. MwMid. Mw Low MwLow Mw
32 nm hpHigh MwHigh Mw
Mid. MwMid. Mw Low MwLow Mw Low Mw +Low Mw +bulky PAGbulky PAG
Low Mw +Low Mw +bulky PAGbulky PAG
Smoothing effectSmoothing effectby acid diffusion?by acid diffusion?S
hort
rang
e LW
R, n
m
0
2
4
6
8
0 10 20 30EL of 45 nm HP, %
0 10 20 30EL of 45 nm HP, %
Sho
rt ra
nge
LWR
, nm
0
2
4
6
8
10
12
Page 33 October 19, 2009
4. Summary
Today, 25nm HP resolution, 5nm LWR and 12mJ/cm2 sensitivity have been demonstrated, but these are still far behind the target at present.Our design policy to improve RLS further consists of enhancementof aerial image contrast and minimization of dissolution unit size.The enhancement of aerial image contrast could be achieved by the following ways.
Enhance electron and acid generationReduce electron and acid diffusion
Some concrete examples to enhance acid generation and reduce electron and acid diffusion are presented to be effective to improve RLS. Further investigation must be necessary to meet the target.It would be also important to realize minimization of the dissolution unit size.
Page 34 October 19, 2009
Acknowledgement
Mr. Kawamura and Dr. Itani from Selete Prof. Tagawa and Prof.Kozawa from Osaka University