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2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Relationship between resist outgassing and activation energy for EUV and EB
Isamu Takagi, Takeshi Sasami, Toru Fujimori, Shinya Minegishi, Yukiko Kikuchi, Eishi Shiobara, Hiroyuki Tanaka, and Soichi Inoue
EUVL Infrastructure Development Center, Inc. (EIDEC)
Takeo Watanabe, Tetsuo Harada and Hiroo Kinoshita Laboratory of Advanced Science and Technology for Industry, University of Hyogo
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Outline
2
Introduction
Objective of this work
Experiment & result
Relation between the outgassing and the activation energy of the protecting group
Relation between the outgassing and the quencher loading
Summary
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Outline
3
Introduction
Objective of this work
Experiment & result
Relation between the outgassing and the activation energy of the protecting group
Relation between the outgassing and the quencher loading
Summary
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Resist-induced Optics Contamination
4
Outgassing from EUV resist will result in optics contamination.
Before resists can be used on the EUV scanner, testing by witness sample (WS) method is necessary.
Mask
Projection Optics
Outgassing
Resist
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Process Flow of Outgassing Test (WS Method)
5
Mask
Projection Optics
Outgassing
Resist
E-gun E-gun
WS
Resist
Ex)EUVOM-9000 Side-view
Outgassing
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Process Flow of Outgassing Test (WS Method)
6
WS
Spectroscopic Ellipsometer
Witness Sample (WS)
Outgas
EUV light
or Electron beam (EB)
Contamination film
2. Film Thickness (FT)
measurement
WS
X-ray
e
XPS
4. Non-cleanable
element evaluation
WS
H-cleaner
Hydrogen radical
3. Hydrogen cleaning
1. Contamination
film growth
Contamination Growth (CG)
Spec. : OK or NG
dR/R calculated from XPS data
Spec. : OK or NG
If both OK, the resist can be exposed in scanner.
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Outline
7
Introduction
Objective of this work
Experiment & result
Relation between the outgassing and the activation energy of the protecting group
Relation between the outgassing and the quencher loading
Summary
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Objective of This Work
8
Clarify the relationship between outgassing and the protecting group.
Size of protecting group
Activation energy (Ea) for de-protection
Ex.) Components of model resist
Base resin PAG Quencher
Protecting group
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Outline
9
Introduction
Objective of this work
Experiment & result
Relation between the outgassing and the activation energy of the protecting group
Relation between the outgassing and the quencher loading
Summary
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Sample name A-1 B-1 C-1 D-1
Base resin
De-protection group (Mw) 148 162 176 82
Relative acid rate constant (k)
1.0 3.6 12.1 2.9
PAG 20 phr*
Quencher
0.1 mol for PAG
Composition of Model Resists in This Work
10
N
S+ C4F9SO3-
*per hundred resin
OH
O O
30 70
OH
O O
30 70
OH
O O
30 70
OH
O O
30 70
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Outgassing Evaluation Tool and Condition
11
EB - EUVOM-9000 -
EUV - HERC* analysis tool -
Tool Geometry
Witness Sample (WS)
Ru 50 nm
Si-sub. Ru 5 nm
Si-sub. Mo/Si ML
*: HERC = High power EUV Resist Contamination
@ NewSUBARU BL9c
Undulator Light
WS
27o
320 mW/cm2
120 mW/cm2
Top-view
E-gun 2 keV
E-gun 0.25 keV
WS
Resist
Side-view
Evaluation tool
Resist process condition Substrate Si (w/ HMDS)
Resist thickness 60 nm
PAB/PEB 100oC 60s / 100oC 60s
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Result of Contamination Growth (CG) Test
12
Big difference in CG depending on protecting group was observed.
0.64
4.44
15.38
7.39
0
5
10
15
20
A-1 B-1 C-1 D-1
CG
(n
m)
Note : All of CG data is scaled to get to 300 mm full wafer exposure.
EB
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
A-1
B-1
C-1
D-1
R² = 0.05
0
5
10
15
20
0 50 100 150 200 250
CG
(n
m)
Mw of de-PG
CG vs. Size of De-protection Group (De-PG)
13
No correlation observed between CG and the de-PG size.
EB
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Relation between CG and k
14
A-1 B-1
C-1
D-1 R² = 0.90
0
5
10
15
20
0.0 5.0 10.0 15.0
CG
(n
m)
k
CG seems to correlate with k.
EB
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
B-1
D-1
0
5
10
0 50 100 150 200
CG
(n
m)
Mw of de-PG
Protecting Group Size Dependency
15
In the case of sample with similar acidic reactivity, the larger de-PG was observed to have lower CG.
EB
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Relation between CG and k’
16
A-1
B-1
C-1
D-1
0
5
10
15
20
0.00 0.02 0.04 0.06 0.08
CG
(n
m)
k’
Considering both k and de-PG size parameters, strong correlation between CG and k’ observed.
This means higher outgassing risk at higher k’.
EB
k’ = k/(Mw of de-PG)
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
EB vs. EUV
17
A-1
B-1
C-1
D-1
A-1 B-1
C-1
0
1
2
3
4
0
5
10
15
20
0.00 0.02 0.04 0.06 0.08
CG
(n
m)
@ E
UV
CG
(n
m)
@ E
B
k’
EB
EUV based tests confirm that k’ can explain the relationship between CG and the characteristics of PGs. D-1 has not been evaluated at EUV. Future test is planned.
EUV
k’ = k/(Mw of de-PG)
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Outline
18
Introduction
Objective of this work
Experiment & result
Relation between the outgassing and the activation energy of the protecting group
Relation between the outgassing and the quencher loading
Summary
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Sample name A-1 / A-2 B-1 / B-2 C-1 / C-2 D-1 / D-2
Base resin
De-protection group (Mw) 148 162 176 82
Relative acid rate constant (k)
1.0 3.6 12.1 2.9
PAG 20 phr*
Quencher
(mol for PAG) 0.1 / 0.2 0.1 / 0.2 0.1 / 0.2 0.1 / 0.2
Composition of Model Resists in This Work
19
N
S+ C4F9SO3-
*per hundred resin
OH
O O
30 70
OH
O O
30 70
OH
O O
30 70
OH
O O
30 70
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
E0 Sensitivity
20
EB
A-1 A-2 B-1 B-2 C-1 C-2 D-1 D-2
E0
(uC/cm2) 1.63 2.63 1.23 2.68 1.31 2.66 1.06 2.17
0
0.5
1
1.5
2
2.5
3
A-1 A-2 B-1 B-2 C-1 C-2 D-1 D-2
E 0 (
uC
/cm
2)
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Relation between CG and k’ in Quencher Loading Difference
21
Higher CG was found at increased k’ and quencher loading.
EB
A-2 B-2
C-2
D-2
A-1 B-1
C-1 D-1 0
20
40
60
80
100
0.00 0.02 0.04 0.06 0.08
CG
(n
m)
k’
Quencher = 0.2mol of PAG
Quencher = 0.1mol of PAG
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
What’s Contributor to CG ?
22
EB
Outgassing species was evaluated by Residual Gas Analysis (RGA)
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Outgassing Species for Each Samples
23
39 51
78
109 119
186 0.0E+00
5.0E-07
1.0E-06
1.5E-06
2.0E-06
2.5E-06
12
14
16
18
11
01
12
11
41
16
11
81
amu
39 51
78
109 119 186
0.0E+00
5.0E-07
1.0E-06
1.5E-06
2.0E-06
2.5E-06
12
14
16
18
11
01
12
11
41
16
11
81
amu
39
51
78
109
119
186
0.0E+00
5.0E-07
1.0E-06
1.5E-06
2.0E-06
2.5E-06
12
14
16
18
11
01
12
11
41
16
11
81
amu
A few species attributed to the de-PG detected at A-2 and B-2.
Species attributed to the de-PG relatively abundant at C-2 and D-2.
Numbered amu (39,51,78,109,119 and 186) are attributed to the PAG
A-2 B-2 C-2
39
51 78
109 119
186 0.0E+00
5.0E-07
1.0E-06
1.5E-06
2.0E-06
2.5E-06
12
14
16
18
11
01
12
11
41
16
11
81
amu
Part
ial pre
ssure
(P
a) D-2
EB
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Correlation between CG and Total Outgassing
24
CG correlates roughly with total outgassing which is the sum of partial pressures of each amu.
1.75 7.95
76.36
10.52
0.0E+00
5.0E-06
1.0E-05
1.5E-05
2.0E-05
2.5E-05
3.0E-05
0
20
40
60
80
100
A-2 B-2 C-2 D-2
Tota
l ou
tgas
sin
g (P
a)
CG
(n
m)
Total outgassing
CG
EB
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Contributor to CG
25
1.75 7.95
76.36
10.52
0.0E+00
5.0E-06
1.0E-05
1.5E-05
2.0E-05
2.5E-05
3.0E-05
0
20
40
60
80
100
A-2 B-2 C-2 D-2
Tota
l ou
tgas
sin
g (P
a)
CG
(n
m)
Total outgassing
Total pressure of PAG contribution
CG
EB
The main contributor to CG is de-PG species.
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Why the CG Increases Drastically at C-2?
26
A-2 B-2
C-2
D-2
A-1 B-1
C-1 D-1 0
20
40
60
80
100
0.00 0.02 0.04 0.06 0.08
CG
(n
m)
k’
Quencher = 0.2mol of PAG
Quencher = 0.1mol of PAG
E0=1.31 uC/cm2
E0=2.68 uC/cm2
Protecting group was de-protected by the increased dose?
EB
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Why the CG Increases Drastically at C-2?
27
A-2 B-2
C-2
D-2
A-1 B-1
C-1
D-1 0
20
40
60
80
100
0.00 0.02 0.04 0.06 0.08
CG
(n
m)
k’
Quencher = 0.2mol of PAG
Quencher = 0.1mol of PAG
Protecting group was de-protected by the increased dose?
C-0 (with only base resin) had similar CG to background.
De-protection reaction is stimulated by acid generated from PAG, and not by the increased dose directly.
C-0 exposed
at 2.68 uC/cm2
(E0 of C-2)
EB
E0=2.68 uC/cm2
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
CG Proportionality to Dose
28
EB
Dose A
cid
concentr
ation
gen
era
ted
fro
m P
AG
Acid concentration
generated from PAG
CG
Dose
?
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
0
100
200
300
400
500
600
0 1 2 3 4
CG
(n
m)
Dose (uC/cm2)
C-2 : quencher = 0.2 mol
C-1 : quencher = 0.1 mol
CG Proportionality to Dose
29
CG is not proportional to the dose even while acid concentration is proportional to the dose.
Assumption: De-protection reaction rate is proportional to the power of acid concentration.
De-protection reaction equation
d[P]/dt = - Kdp ・[P] ・ [H+]m
[P] : normalized PG conc.
[H+] : normalized acid conc.
Kdp : de-protection rate const.
m : de-protection reaction order
t : time
EB
E0 = 1.31 uC/cm2
E0 = 2.68 uC/cm2
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Outline
30
Introduction
Objective of this work
Experiment & result
Relation between the outgassing and the activation energy of the protecting group
Relation between the outgassing and the quencher loading
Summary
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Summary
31
In order to understand the mechanism to mitigate outgassing, the relationship between outgassing and the protecting group was studied.
Results suggest that the risk of outgassing becomes higher in proportion to k’ ( = Relative acid rate constant / de-protection group size) .
Good correlation between CG and k’ was observed on both EB and EUV.
Drastic increase of CG confirmed to be mainly due to the de-PG, in a combination of low k’ and high quencher loading.
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Acknowledgement
32
This work was supported by New Energy and Industrial Technology Development Organization (NEDO).
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014 33
Thank you for your kind attention!
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014 34
Supporting slide
2014 International Symposium on Extreme Ultraviolet Lithography, Washington, D.C., USA 28 Oct., 2014
Analysis of De-Protecion Reaction Kinetics
35
Ref.: O. Nakayama et.al., Proc. SPIE 6923, 135 (2008).
Monomer Each 2.73E-04 mol
Acid Benzoic Acid 1.1eq 2.73E-04mol
Solvent 1,1,2,2-tetrachloroethane-d2 0.69mL
NMR-tube
Heating 130 oC Time 0 s 300 s 600 s 1200 s
Cooling < 6 oC Time 5 min.
NMR analysis Methacrylic acid
Monomer
The reaction conversions were calculated from these integral values.
-6
-4
-2
0
0 500 1000 1500
LN(1
-X)
time (s)
-kt=LN(1-X) k:reaction constant t:time(s) X:conversion ratio
Large k = high acidic reactivity = Low Ea