USE OF DSA TO RECTIFY LCDU OF EUV EXPOSED CONTACT...
Transcript of USE OF DSA TO RECTIFY LCDU OF EUV EXPOSED CONTACT...
© IMEC 2013
USE OF DSA TO RECTIFY LCDU OF EUV EXPOSED CONTACT HOLES
ROEL GRONHEID, ARJUN SINGH
TODD R. YOUNKIN
© IMEC 2013
OUTLINE
DSA
▸ Grapho-epitaxy: EUV NTD resist + homo-polymer blend
- Limitations of this process: ~20nm
- Challenges to implement BCP into similar flow
▸ Chemo-epitaxy:
- Honeycomb process flow + results
- Data on CDU improvement and critical contributors to CDU in current
process
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USE OF (BLOCK CO) POLYMERS TO
REPAIR CDU
K. Maruyama et al. – EUVL Symposium 2012
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Poly(A-block-B)
Cylinder (hole) CD is determined by polymer chain length
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DSA SHRINK BEHAVIOR THROUGH DOSE
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DSA blended agent requires closed pre-pattern and saturates ~ 25-30 nm.
May be used as CDU enhancement?
48P80 40hp
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Resist NTD PTD
Shrink None Shrink A, Std
FT Shrink A, FT+ Shrink A, FT++ None
Image
Esize
(mJ/cm2) 23.5 20.8 (11 %) 20.4 (13 %) 17.0 (27 %) 17.0
CD (nm) 32.5 30.2 29.2 27.3 30.4
CDU (nm) 1.4* 1.3* 1.3 1.0 --
* Missing holes observed; Believed to arise from NTD pre-pattern
Optimization = Shrink FT > Resist FT >> Resist Anneal > Shrink Anneal
Process optimization yielded ~10-25% Esize Gain at 30 hp vs. NTD
Process does not scale well below ~25nm CD; material modification may
be required for these dimensions
38P60 30hp
Key Parameter = DSA Shrink Agent FT
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GRAPHO-EPITAXY FLOW USING HOMO-
POLYMER BLENDS
K. Maruyama et al. – EUVL Symposium 2012
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use block copolymer instead of homo-polymer
better CDU improvement?
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GRAPHO-EPITAXY WITH BCP
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193nm pre-pattern
Pst-Litho Pst-HardBake Pst-DSA
+ Wet Dev
SEM image
CD (nm) 53.8 58.9 14.5
Change (nm, %) -- +5.1, +9.5% -44.4, -75.4%
Net Shrink (nm, %) -- -- -39.3, -73.0%
CD Range (nm) 3.4 3.3 0.5
1 2 3
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PROPOSED CHEMO-EPITAXY FLOW
anneal
Etch X-PS
and strip
resist
Coat
BCP
Coat X-PS
+EUV resist
Pattern
hexagonal hole
array by EUV
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PMMA
removal
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HEXAGONAL CONTACT ARRAYS DENSE
Center-to-center distance same in
all directions
9
p
p
Honeycomb reticle is available and prints target structures
p=54nm; exposed on NXE:3100
Mask patterns
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PROCESS OPTIMIZATION
Large L0 BCP materials are not easy to work with
▸ Material preparation/tuning proves more challenging than for
smaller L0
▸ Larger L0 BCP have smaller process windows for neutral layer,
film thickness, pre-pattern pitch, ...
▸ For cylindrical PS-b-PMMA operational L0 window ~30-60nm
- Little overlap with
processing window
for EUV patterned
contact holes
10
p54nm
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EUV CDU REPAIR WITH HONEYCOMB 27NM HALF PITCH
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Post-litho Post-BCP anneal Post-PMMA
removal
1s CDU: 2.1-2.5nm 1s CDU: 1.6-1.7nm
Residual CDU to be improved by
process and material optimization
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HEXAGONAL ARRAY THROUGH PITCH
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Pitch 50 Pitch 52 Pitch 54 Pitch 56
Pre-pattern
BCP
Pitch 58 Pitch 60 Pitch 62 Pitch 64
Pre-pattern
BCP
• For current BCP material
we see best performance
for 54 – 58 nm pitch
• BCP performance is
mostly independent of pre-
pattern hole CD
• It’s possible that it works
for tighter pitches but pre-
pattern not good enough
(yet)
• Smaller L0 BCP materials
generally work better:
process benefits expected
to increase on NXE:3300
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SQUARE ARRAY THROUGH PITCH
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Pitch 52 Pitch 54 Pitch 56 Pitch 58
Resist only
BCP
• Annealed at 275 ℃ for 5 minutes
• Best performance for 54 – 56 nm pitch
• DSA process works, but pattern quality is clearly impacted by
forced snapping to square gridded layout
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HEXAGONAL CONTACT ARRAYS MISSING HOLES
Only purple holes are printed to
mimic missing patterns
p
p
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p=54nm
Mask patterns
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HEXAGONAL ARRAYS WITH MISSING
HOLES
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Pitch 54 Pitch 56 Pitch 58
• Repair works, but success rate is not yet sufficient
• Expected to improve with process optimization and material tuning
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SUMMARY
300mm wafer processes for DSA-based hole patterning for EUV
LCDU rectification have been set up at imec
Grapho-epitaxy based on homo-polymer blends works, but only
to keep relative CDU performance in combination with shrink
Grapho-epitaxy based on BCP requires very large initial hole CD
and may not be attractive path for dense hole patterns
Chemo-epitaxy DSA flow with BCP looks promising, but does
not yet meet requirements
More work is needed to understand how BCP material and
process impacts CD uniformity
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