© IMEC 2014
VARIABILITY OF EUV RESIST OUTGAS TEST RESULTS : COMPARISON OF OUTGAS VERSUS CONTAMINATION BEHAVIOR AT MULTIPLE TEST SITES USING MODEL EUV RESISTS
I. POLLENTIER, Y.C. LIN, A. TIRUMALA VENKATA, G. VANDENBERGHE, IMEC
R. F. BERG, S. HILL, C. S. TARRIO, T. B. LUCATORTO, NIST
E. SHIOBARA, Y. KIKUCHI, T. SASAMI, S. INOUE, EIDEC
© IMEC 2014
OUTLINE
Introduction : round robin variability
RGA outgas metric for contamination
Within-site relationship of outgas/contamination
Site-to-site relationship of outgas/contamination
How to use outgas contamination relationship towards
‘round robin’ variability ?
Summary
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014 2
© IMEC 2014
OUTGAS TESTING
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014
[N. Harned, IEUVI ResistTWG, Feb’2014]
‘cleanable
contamination’
‘non-cleanable
contamination’
CC ≤ 3nm10nm (NXE3100)
CC ≤ 3nm10nm (NXE3300)
NCC ≤ 0.23% (NXE3100)
NCC ≤ 0.16% (NXE3300)
Example of Contamination Growth (CG)
tester (imec)
Resist outgassing is potential risk for
NXE:3x00 and needs to be tested
according to a procedure
Different outgas test qualification sites have different
test infrastructure, resulting in variability (‘round
robin’ testing) despite the well-defined procedure. 0
1
2
3
4
5
6
7
8
9
10
Resist1 Resist2 Resist3 Resist4C
G (
nm
) site 1
site 2
site 3
site 4
site 5
[‘Round Robin 2’ reported at IEUVI
Resist TWG meeting, Feb’ 2014]
spec
Witness sample
3
© IMEC 2014
ROUND ROBIN VARIABILITY
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014
In order to reduce the gap of inter-site CG variability, collaborative work is done
in between EIDEC, NIST, Sematech, and imec under advice of ASML (reported in
detail on recent IEUVI resist TWG meeting), and 3 main root causes of variability
have been identified.
T. Lucatorto (NIST), IEUVI ResistTWG, Feb’ 2014]
Temperature Stability in time is key, and site-to-site
matching needs to be checked.
Contamination limited
regime (CLR)
Intensity of WS exposure needs to be
sufficiently high. Non-CLR can
underestimate the contamination.
OK not
OK
CG spot on
witness sample
A/PS ratio
(A :wafer area;
PS : pumping speed)
Different outgas test sites expose
different wafer areas, and the pumping
speed of testers are different. ASML
proposed to use common A/PS ratio
4
© IMEC 2014
ROUND ROBIN VARIABILITY
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014
The goal of this presentation is to validate and show progress,
but also to include RGA as complementary information 5
Presented by S. Inoue (EIDEC), IEUVI Resist TWG meeting, Washington, Oct’2014
© IMEC 2014
OUTLINE
Introduction : round robin variability
RGA outgas metric for contamination
Within-site relationship of outgas/contamination
Site-to-site relationship of outgas/contamination
How to use outgas contamination relationship towards
‘round robin’ variability ?
Summary
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014 6
© IMEC 2014
PRIOR WORK ON RGA CG CORRELATION TO CG
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014
Integrated COR can be considered
as independent & complementary
measurement to the CG
I. Pollentier et al, SPIE 2013
RGA
Inte
gra
ted C
OR
CG (nm)
Supplier 1
Supplier 2
Supplier 3
Supplier 4
Supplier 5
integrated COR
(contaminating
outgassing rate)
contamination
growth (CG)
WS
Cut = 55amu
Power = 0.5
7
© IMEC 2014
OUTLINE
Introduction : round robin variability
RGA outgas metric for contamination
Within-site relationship of outgas/contamination
Site-to-site relationship of outgas/contamination
How to use outgas contamination relationship towards
‘round robin’ variability ?
Summary
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014 8
© IMEC 2014
WITHIN-SITE OUTGAS/CONTAMINATION
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014
Model resists provided by EIDEC
EIDEC distributed 5 model resists amongst the
qualification sites for next step round robin; Two resists
are expected to be high contaminating (CG = 7-10nm)
CG testing at imec
Contamination limited
regime (CLR)
Intensity of WS exposure needs to be
sufficiently high. Non-CLR can
underestimate the contamination.
OK not
OK
CG spot on
witness sample
A/PS ratio
(A :wafer area
PS : pumping speed)
Different outgas test sites expose
different wafer areas, and the pumping
speed of testers are different. ASML
proposed to use common A/PS ratio
EUV vs. E-gun
9
© IMEC 2014
WITHIN-SITE OUTGAS/CONTAMINATION
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014
Model resists provided by EIDEC
EIDEC distributed 5 model resists amongst the
qualification sites for next step round robin; Two resists
are expected to be high contaminating (CG = 7-10nm)
0
0
CG
NX
E Eg
un
(nm
)
CG NXE EUV (nm)Good correlation between EUV exposed and Egun
exposed CG results.
non-CLR ?
All CLR
0
20
40
60
0.00
int
CO
R (
a.u
.)
CG (nm)
Good correlation between outgassing and
contamination.
CG testing at imec
EUV vs. E-gun
RR model resists
other
resists
10
© IMEC 2014
WITHIN-SITE OUTGAS/CONTAMINATION
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014
0
0
CG
NX
E Eg
un
(nm
)
CG NXE EUV (nm)Good correlation between EUV exposed and Egun
exposed CG results.
non-CLR ?
All CLR
0
20
40
60
0.00
int
CO
R (
a.u
.)
CG (nm)
0
0 50 100 150
CG
NX
E (n
m)
e-current WS (uA)
WS testing shows that std
imec condition is in CLR !
non-CLR ?
0
20
40
60
0.00
int
CO
R (
a.u
.)
CG (nm)
RGA confirms that max CG of std condition
meets CLR and even can predict CRL violations !
CG testing at imec
EUV vs. E-gun
11
© IMEC 2014
RR TESTING AT IMEC : A/PS
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014
Area / Pumping Speed
Differences in CG vs. PS slope could be responsible for different CG behavior.
Agreement with integrated COR.
0
40 60 80 100 120
CG
(n
m)
pumping speed (%)
CSR003
CSR019
CSR042
RR2 (Res3)
0
10
20
30
40
40 60 80 100 120
int.
CO
R (
a.u
.)
pumping speed (%)
CSR003
CSR019
CSR042
RR2 (Res3)
(wfr area constant)
Sources of variability (CLR and
PS/A) are confirmed to be
important !
The integrated COR (RGA) can
help in the investigation !
12
© IMEC 2014
OUTLINE
Introduction : round robin variability
RGA outgas metric for contamination
Within-site relationship of outgas/contamination
Site-to-site relationship of outgas/contamination
How to use outgas contamination relationship towards
‘round robin’ variability ?
Summary
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014 13
© IMEC 2014
RGA-CG CORRELATION SITE-TO-SITE
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014
One material evaluated by RGA at 3 different sites.
Similar peak masses are found, however with different relative magnitude.
RGA peak differences can be due
to many reasons :
- RGA hardware and
measurement setting
- Distance and/or line-of-sight
between RGA and wfr
14
© IMEC 2014
R² = 0.96
0
1
2
3
4
5
0
inte
g. C
OR
(n
orm
aliz
ed
to
1 f
or
Res
1)
CG (nm)
2.5
imec
Good correlation both for
commercial resists and model
resist in EUV and Egun
RGA CG CORRELATION AT DIFFERENT SITES ?
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014
EIDEC
0
0.00
int
CO
R (
a.u
.)
CG (nm)
Cut = 55amu
Power = 0.5 R² = 0.67
0
1
2
3
4
5
0
inte
g. C
OR
(n
orm
aliz
ed t
o 1
fo
r R
es1
)
CG (nm)
0.5
Cut = 55amu
Power = 0.5
0
1
2
3
4
5
0
inte
g. C
OR
(n
orm
aliz
ed t
o 1
fo
r R
es1
)
CG (nm)
0.5
Bad correlation !
Good correlation !
Cut = 55amu
Power = 2.5
Use quadratic fits to check
correlation as function of ‘power’
0
1
2
3
4
5
0in
teg.
CO
R (
no
rmal
ized
to
1 f
or
Res
1)
CG (nm)
4
3.5
3
2.5
2
1.5
1
0.5
Cut = 55amu
Power = 0.5 4
15
© IMEC 2014
imec
RGA CG CORRELATION AT DIFFERENT SITES ?
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014
EIDEC
0
0.00
int
CO
R (
a.u
.)
CG (nm)
Cut = 55amu
Power = 0.5
0
1
2
3
4
5
0
inte
g. C
OR
(n
orm
aliz
ed
to
1 f
or
Res
1)
CG (nm)
2.5
Cut = 55amu
Power = 2.5
Power weight needs to be tuned to compensate the lower
detection of peaks at higher amu’s
16
© IMEC 2014
OUTLINE
Introduction : round robin variability
RGA outgas metric for contamination
Within-site relationship of outgas/contamination
Site-to-site relationship of outgas/contamination
How to use outgas contamination relationship towards
‘round robin’ variability ?
Summary
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014 17
© IMEC 2014
0
0.00
int
CO
R (
a.u
.)
CG (nm)
Site A
Away from correlation :
‘mismatch’ between
outgassing and CG
On correlation : outgassing
and CG are ‘matching’
Root cause is (very likely)
contamination ! (e.g. CLR)
2
0
0.00
int
CO
R (
a.u
.)
CG (nm)
USE OF RGA-CG CORRELATION TO (RR)
CG VARIABILITY INVESTIGATION
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014
Is round-robin variability related to variability
in outgassing or contamination ???
1
0
0
inte
g. C
OR
(a.
u.)
CG (nm)
Site B
On correlation : outgassing
and CG are ‘matching’
3
COR can help in this
identification !!!
0
20
40
60
0.00
int
COR
(a.
u.)
CG NXE (nm)
0
20
40
60
0.00
int
COR
(a.
u.)
CG NXE (nm)
0
1
2
3
4
5
6
7
8
9
10
Resist1 Resist2 Resist3 Resist4
CG
(n
m) site 1
site 2
site 3
site 4
site 5
[‘Round Robin 2’ reported at IEUVI
Resist TWG meeting, Feb’ 2014] Site-to-site variability
if RGA/CG correlation is
observed at both sites :
Root cause is
outgassing !
[can still have many sources :
dose, PS/A, ...]
4
0
20
40
60
0.00
int
COR
(a.
u.)
CG NXE (nm)
0
20
40
60
0.00
int
COR
(a.
u.)
CG NXE (nm)
Example of resist
0
20
40
60
0.00
int
COR
(a.
u.)
CG NXE (nm)
18
© IMEC 2014
0
20
40
60
0.00
int
CO
R (
a.u
.)
CG NXE (nm)
Novel inorganic materials have been explored at imec
towards outgassing
USE OF RGA-CG CORRELATION FOR
ALTERNATIVE RESIST MATERIALS
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014
Commercial and model
resists tested (CAR)
Alternative resists
(non-CAR)
Outgassing vs. contamination
relationship is slightly different
compared to CAR.
Low ‘cleanable’ contamination is
feasible.
More investigation is required to check if current outgas test
procedure needs to be revised for the alternative materials.
19
© IMEC 2014
OUTLINE
Introduction : round robin variability
RGA outgas metric for contamination
Within-site relationship of outgas/contamination
Site-to-site relationship of outgas/contamination
How to use outgas contamination relationship towards
‘round robin’ variability ?
Summary
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014 20
© IMEC 2014
SUMMARY
In order to decrease the round robin variability between outgas sites,
collaborative work is done between the outgas qualification sites in close
cooperation with ASML. Control on key parameters such as temperature, CLR,
and PS/A has found to be important.
In addition to the contamination growth (CG) from the witness sample testing,
benefit has been found in the RGA outgas measurement, where simple analysis
can provide complementary information (integrated COR). This RGA parameter
is typically correlating very well with CG, and this correlation has been
demonstrated on multiple sites.
It is expected that this approach is helpful in identification of within-site and site-
to-site excursions of contamination results and help in understanding of
contamination processes of advanced photoresists.
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014 21
© IMEC 2014
ACKNOWLEDGEMENTS
ASML : S. van Pham, G. Rispens, and N. Harned
D. De Simone, and E. Hendrickx (imec) and Resist suppliers for
providing resist samples and helpful discussions.
EUV Tech : C. Perera and D. Houser
I. POLLENTIER - EUVL SYMPOSIUM, WASHINGTON, 28 OCT 2014 22
© IMEC 2014