Printability, Inspectability and Repair Process Assessment

2008 International Symposium on Extreme Ultraviolet Lithography
Characterization of EUV Mask Defects:
Printability and Repair Process
Hakseung Han*, Donggun Lee, Hwan-Seok Seo, Kenneth A. Goldberg**,
Hoon Kim, Byung-Sub Ahn, In-Yong Kang, Wonil Cho, Sanghyeon Lee,
Suyoung Lee, Geunbae Kim, Dongwan Kim, Seong-Sue Kim, and HanKu
Cho
Memory R&D Center Samsung Electronics Co., Ltd.
**CXRO, Lawrence Berkeley National Lab.
*[email protected]
2/total
3/total
Absorber defect printability
ADT Printability (45nm HP) - Intrusion
z Intrusion type defects were formed ranging from ~14nm(4X).
z Intrusions larger than ~40nm on mask are printable.
Mask SEM Image
14.1nm
25.4nm
Wafer SEM Image
29.0nm
41.0nm
60.6nm
Printable
78.4nm
Measured defect
size (on mask)
[nm]
ADT Printability (32nm HP) - Intrusion
z Intrusions larger than ~40nm on mask are printable.
z Difficult to analyze due to large resist LER .
Mask SEM Image
19.6nm
35.0nm
Wafer SEM Image
41.6nm
54.4nm
111nm
111nm
Measured defect
size (on mask)
[nm]
ADT Printability (45nm HP) - Extrusion
z Extrusions larger than ~40nm on mask are printable.
z Failed to get printability about extrusions on 32nm Line .
Mask SEM Image
24.4nm
26.5nm
47.8nm
Wafer SEM Image
7/total
57.7nm
71.6nm
86.5nm
104.2n
m
ADT Printability (45nm HP) - Contact
z Defect size defined from virtual edge
z Defects larger than ~35nm are printable.
Defect size
Definition
Mask SEM Image
24.2nm
27.4nm
Wafer SEM Image
33.0nm
39.1nm
41.9nm
47nm
53.2nm
57.0nm
Printability Simulation(45nmHP) - Intrusion
zTh’shold
CD was obtained with varying defect width without
shadowing effect.
z15nm(60nm on mask) square makes CD change more than 5%.
z Less printable than ADT test Æ LER & Process dominant.
Assuming Square defect.
5%
10%
9
Printability Simulation(32nmHP) - Intrusion
z
12nm(48nm on mask) square makes CD change more than 5%.
Assuming Square defect.
5%
10%
Printability Simulation(45nmHP) - Extrusion
8nm(32nm on mask) square makes CD change more than 5%.
Printable defect size from simulation roughly matches ADT
printability data between 5% and 10%.
z Extrusion type shows much tighter spec. than intrusion.
z
z
Assuming Square defect.
5%
10%
Printability Simulation(32nmHP) - Extrusion
z
6nm(24nm on mask) square makes CD change more than 5%.
Assuming Square defect.
5%
10%
Simulation Comparison with ADT result
Simulation underestimates printability for intrusion type.
It is likely test result could be misunderstood due to process
effect.
z
z
Simulation ( 5 ~ 10 %)
ADT test ( Roughly
measured)
45nm Int. 32nm Int. 45nm Ext. 32nm Ext.
13
SEMATECH/Berkeley MET
5X reduction, 0.3 NA
(synchrotron source)
CCD
mask
SEMATECH/Berkeley AIT
~0.35 NA, 0.2σ
14/total
Repair Process Development- Ebeam Repair
z
z
z
450nm Bridge Defects were repaired and evaluated using the AIT.
Process tuning needed due to Buffer layer(B) Æ Ru Cap. Preferred.
After fine tuning, repair processes (C,D) worked well.
BF-120
BF-60
BF
A
Ref.
B
C
D
15/total
BF+60
BF+120
Ebeam Repair Process
z Measured Th’hold CD through focus.
z Case D showed enough process margin about 200nm.
D
C
Spec(10%)
16/total
Nano-machining Repair Process
z Extrusion(75nm x 150nm) on 150nm Line was repaired and
evaluated using Nano-machinning repair.
z Showed good feasibility.
BF-120
BF-60
BF
BF+60
BF+120
A
Ref.
B
Refer to paper
by Dr. Suyoung
Lee at BACUS 08
for more details
C
D
17/total
Nano-machining Repair Process
z
z
z
Confirmed again using MET.
5x demagnification exposure and 30nm HP L&S images.
Appears process margins are enough.
BF-100
d0 – 15%
BF-50
BF
BF+50
d0 – 5%
d0 – 10%
18/total
BF+100
d0
Nano-machining Repair Process
z Missing contact hole repaired and evaluated using AIT and
showed good feasibility.
z Aerial imaging is very useful for defect printability-related
analysis, much more convenient than using wafer exposure.
Ref.
Repaired
Ref.
Repaired
19/total
Repaired
Ref.
20/total
The authors would like to thank…
z Jinhong Park and Junghoon Lee at Process Development Team for
measuring wafer printed at ADT and other ADT related engineers in IMEC
and ASML,
z Iacopo Mochi for measuring aerial image from the AIT,
z Dr. Patrick Naulleau, Paul Denham, Brian Hoef, and Gideon Jones for
their helps for the wafer printing test using EUV MET at ALS in LBNL.
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