The effects of guide pattern
roughness on directed selfassembly line-space patterns
Katsutoshi Kobayashi a), Yusuke Kasahara a), Ken Miyagi
b), Katsumi Ohmori b), Shinichiro Kawakami c), Takashi
Yamauchi c), Takahiro Kitano c), Masayuki Shiraishi d) and
Hisako Aoyama a)
a)Toshiba, b)Tokyo Ohka Kogyo, C)Tokyo Electron Kyushu
d)Nikon
Outline
• Background
• Process
– COOL (Coordinated line epitaxy)
– Grapho-epitaxy (Resist guide pattern)
• Measurement method of DSA pattern placement error
• The optimization of the SEM parameters on CD measurement
• Results
– COOL process
– Grapho-epitaxy process
• Summary
2
Placement error of DSA lithography
Conventional lithography
overlay
DSA lithography
(a)
upper
layer
pattern
guide
pattern
under
layer
pattern
under
layer
pattern
(b)
overlay
overlay
DSA
pattern
<DSA lithography>
Placement error will occur during both resist guide pattern exposure (a) and the
DSA patterning process (b)
3
Factors of DSA pattern placement error
DSA pattern roughness
DSA
pattern
DSA
pattern
guide
pattern
guide
pattern
(Material)
- Type of BCP
- PDI of BCP
- Neutral layer
material
Guide pattern
(Process)
- BCP film thickness
- Annealing time
etc.
*BCP : block co-polymer
*PDI : polydispersion index
- CDU
- LWR/LER
- Height
etc.
*CDU : critical dimension uniformity
*LWR : line width roughness
*LER : line edge roughness
This study will discuss the effect of the guide pattern roughness on
the placement error of DSA line-space patterns
4
COOL & Grapho-epitaxy process
COOL
Resist
Patterning
Resist
SOG
Grapho-epitaxy
Resist
Patterning
SOC
Resist Trim
SOG Partial Etch
Neutral Layer
Graft & Rinse
BCP coat
Anneal
*COOL : EIDEC original flow
SiO2
Deposition
SOG
SOC
sub.
Additional
process
Resist
Smoothing
SOG
SOC
sub.
Neutral layer
Brush
BCP coat
& Anneal
Development
Development
<Advantages of COOL>
• No special pinning guide material required
• No resist stripping required
Ref. : Y. Seino, et. al., Microelectronic Engineering 134 (2015) 27
5
Original measurement method of placement error
COOL
Space1
Line2
Grapho-epitaxy
Space2
Line1
Space1
Line1
Line2
Space2
Space3
Line3
guide
pattern
guide
pattern
CD1
(Line2 + Space1)
CD2
(Line3 + Space2)
CD1
(Line1 + Space2)
Line1
Space1
Line2
CD2
(Line2 + Space3)
Space1
Space2
Line3
Space2
Line1
Space3
Line2
6
Original measurement method of placement error
COOL
Space1
Line2
Line1
Grapho-epitaxy
Line1
Space2
Space1
Space2
Line2
Space3
Line3
guide
pattern
guide
pattern
CD1
(Line2 + Space1)
CD2
(Line3 + Space2)
CD1
(Line1 + Space2)
CD2
(Line2 + Space3)
Space1
<this study> Line1
Space2
Space3
DSA pattern
placement
Space1
Space2 error =
(COOL) :
Line1
Line2
Δline1Line2
= |CD1-CD2|
+ 3 sigma
Line3
*Assumption : the relative distance between the guide pattern
and the line of each side is the same
(Grapho-epitaxy) :
Δspace1 = |CD1-CD2| + 3 sigma
7
The optimization of inspection area
Narrow Inspection Area
Inspection
Area
DSA pattern
guide
pattern
DSA pattern
position
<Narrow inspection area>
The DSA pattern position is strongly
influenced by the DSA pattern roughness
Wide Inspection Area
Inspection
Area
DSA pattern
position
<Wide inspection area>
The error influenced by the DSA
pattern roughness becomes smaller
8
The optimization of inspection area
Narrow Inspection Area
Inspection
Area
DSA pattern
Inspection
Dependency on inspection
area
Area
4
Placement error (nm)
Wide Inspection Area
3.5
3
2.5
2
1.5
1
0.5
0
0
guide
pattern
100
200
300
400
500
Inspection Area (nm) DSA pattern
DSA pattern
position
<Narrow inspection area>
The DSA pattern position is strongly
influenced by the DSA pattern roughness
600
position
<Wide inspection area>
The error influenced by the DSA
pattern roughness becomes smaller
9
The optimization of measurement point
Few Measurement Points
DSA pattern
position
guide pattern
Numerous Measurement Points
DSA pattern
position
DSA pattern
<Few measurement points>
The DSA pattern position is strongly
influenced by the DSA pattern roughness
<Numerous measurement points>
The error influenced by DSA pattern
roughness becomes smaller
10
The optimization of measurement point
Few Measurement Points
Numerous Measurement Points
DSA pattern
position
DSA pattern
position
Placement error (nm)
Dependency on measurement point
3
2.5
2
1.5
1
guide pattern
0
100
200
300
400
Measurement point
DSA pattern
<Few measurement points>
The DSA pattern position is strongly
influenced by the DSA pattern roughness
500
<Numerous measurement points>
The error influenced by DSA pattern
roughness becomes smaller
11
Outline
• Background
• Process
– COOL (Coordinated line epitaxy)
– Grapho-epitaxy (Resist guide pattern)
• Measurement method of DSA pattern placement error
• The optimization of the SEM parameters of CD measurement
• Results
– COOL process
– Grapho-epitaxy process
• Summary
12
Results of COOL and grapho-epitaxy process
COOL
Placement
error
Resist A
Resist B
LWR : 1.83
LER : 2.04
LWR : 1.45
LER : 1.68
1.84
1.46
Grapho
-epitaxy
without
smoothing
LWR : 4.14
LER : 3.03
Placement
error
4.62
with
smoothing
LWR : 3.62
LER : 2.47
2.61
The improvement in the guide pattern roughness leads
to the reduction in the DSA pattern placement error
13
5
4
3
COOL
2
1
Grapho-epitaxy
0
0
1
2
3
4
5
LWR of guide pattern/ nm
Placement error / nm
Placement error / nm
Guide pattern LWR/LER vs Placement error
5
4
3
2
1
0
0
1
2
3
4
5
LER of guide pattern/ nm
14
COOL and grapho-epitaxy process
Grapho-epitaxy
COOL
The grapho-epitaxy process is more strongly influenced by
the guide pattern roughness than the COOL process is
15
Summary
• The DSA pattern placement error of the grapho-epitaxy
process is more strongly influenced by the guide
pattern roughness compared to that of the COOL
process
• In order to reduce the DSA pattern placement error, it is
important to improve the roughness of the guide
pattern. So, in future development, we need to consider
the advancement of the guide pattern performance, so
that we can utilize the DSA technology as the solution
in forthcoming device manufacturing
16
Acknowledgement
• I would like to proffer my thanks to the EIDEC DSA
program for much useful information and advice about
the COOL process technology.
17