Transcript Slide 1

Directly patterning ferroelectric
films by nanoimprint lithography
with low temperature and low
pressure
K.C. Hsieh and H.L. Chien
Department of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan
C.H. Lin
National Nano Device Laboratories, Hsinchu, Taiwan
C.Y. Lee
Department of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan
Journal of Vacuum Science & Technology B 24(6). Nov/Dec 2006, p3234-3236.
Joanne Yim
EE C235/NSE C203
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Outline
• Background
– Why ferroelectric materials?
– Conventional nanoimprint lithography
– Direct nanoimprint on metals
• Method
– Gel precursor
– Au/gel bilayer
• Results
• Summary/Questions Remaining
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Why ferroelectric materials?
• Apply electric field to induce electric dipole
moment
• Used for:
– Memory, sensors, actuators, optoelectronics
• Large-area patterns
• Examples: BaTiO3, PbZrTiO3
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Conventional NIL
• Shape, then
harden some soft
material into relief
of desired pattern
• Transfer pattern to
substrate by
etching
• Processing
speed/resolution
limited by etching
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Direct nanoimprint – previously…
• Semiconductor material
– Excimer laser-assisted
– Requires high power and high pressure
• Metal films
– 100MPa
– Imprinted onto “soft” film
• DIRECT = shape material, not some buffer
– Must be malleable
– Use “sharper” mold to reduce pressure
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Method 1
• MOD (metal organic
decomposition) solution of
Pb(Zr0.52Ti0.48)O3 with excess Pb
• Spin coat ~200nm onto Si
substrate
• 120°C anneal to remove
solvent, make gel & maximize
hardness difference
• Si mold apply at RT, 10-20MPa
• Dry @ 120°C, pyrolyze @
450°C, anneal @ 650-800°C to
obtain perovskite phase
• (higher T anneal = more
complete perovskite structure)
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Method 2
• FE require some
metal contact to
apply electric field
• Apply metal thin
film and shape
along with FE
layer
• Better
– Less sticking
– Less relaxation
after mold release
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Results – FE gel
• After imprint, features ~60nm
high, much less than ~500nm
mold height and gel depth
• gel sticks to mold
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Results – FE gel + Au film
Depth by AFM
•14MPa (top) : 90nm
•20MPa : 300nm
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Summary/Questions remaining
• Malleable precursor can be directly
imprinted
• Combining with top metal film improves
transfer
• Thickness of Au film?
– When will cracking begin?
• Applicability to other material systems?
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