Demonstration of Sub-Rayleigh Lithography Using a Multi-Photon Absorber
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Transcript of Demonstration of Sub-Rayleigh Lithography Using a Multi-Photon Absorber
Demonstration of Sub-Rayleigh Lithography
Using aMulti-Photon Absorber
Heedeuk Shin, Hye Jeong Chang*, Malcolm N. O'Sullivan-Hale, Sean Bentley# , and Robert W. Boyd
The Institute of Optics, University of Rochester, Rochester, NY 14627, USA* The Korean Intellectual Property Office, DaeJeon 302-791, Korea
# Department of Physics, Adelphi University, Garden City, NY
Presented at OSA annual meeting, October 11th, 2006
Motivation
Quantum lithography
Proof-of-principle experiments
Multi-photon lithographic recording material
Experimental results
Non-sinusoidal 2-D patterns
Conclusion & future work
Outline
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Motivation
In optical lithography, the feature size is limited by diffraction, called the ‘Rayleigh criterion’.- Rayleigh criterion : ~ /2
Quantum lithography using an N-photon lithographic recording material & entangled light source was suggested to improve optical lithography.
We suggest PMMA as a good candidate for an N-photon lithographic material.
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Advantage : high visibility is possible even with large resolution enhancement.
Classical interferometric lithography
- , where K = /(2sin)
Resolution : ~ /2 at grazing incident angle
Quantum interferometric lithography uses entangled N-photon light source.
-
Resolution : ~ /2N
Quantum lithography
phase shifter
)cos(12
1KxI
phase shifter
PDC
)cos(12
1NKxI
Boto et al., Phys. Rev. Lett. 85, 2733, 2000
1
1
0,2
2,0
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Fringe patterns on an N-photon absorber with M laser pulses.
The phase of mth shot is given by 2m/M.
The fringe pattern is
Example
Enhanced resolution with a classical light source
S.J. Bentley and R.W. Boyd, Optics Express, 12, 5735 (2004)
M
m
NMmKxI1
)]/)1(2cos(1[
Phase-shifted-grating method
One photon absorberSingle shot
Two-photon absorberTwo shots
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PMMA is a positive photo-resist, is transparent in visible region and has strong absorption in UV region.
3PA in PMMA breaks chemical bonds, and the broken bonds can be removed by developing process. (N = 3 at 800 nm)
UV absorption spectrum of PMMA
PMMA is excited by multi-photon absorption
PMMA as a multi-photon absorber
800 nm
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Experiment – material preparation
Sample preparation 1) PMMA solution PMMA (Aldrich, Mw ~120,000) + Toluene : 20 wt% 2) PMMA film : Spin-coat on a glass substrate Spin coating condition : 1000 rpm, 20 sec, 3 times Drying : 3 min. on the hot plate
Development 1) Developer : 1:1 methyl isobutyl ketone (MIBK) to Isopropyl
Alcohol 2) Immersion : 10 sec 3) Rinse : DI water, 30 sec 4) Dry : Air blow dry
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Experimental setup
Ti:sapphire fs-laser
f1M1
f2M2
PMMA
BS
M3Pol.WP
PR
WP : half wave plate; Pol. : polarizer; M1,M2,M3 : mirrors; BS : beam splitter; f1,f2 : lenses; PR : phase retarder (Babinet-Soleil compensator)
with regenerative amplifcation
120 fs, 1 W, 1 kHz, at 800 nm
(Spectra-Physics)
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Substrate (Glass)
Phase retarder
PMMA
Developing
Path length difference /2
Interference pattern shifted by /4
Experimental process
/2
/4
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Demonstration of writing fringes on PMMA
Recording wavelength = 800
nm Pulse energy = 130 J per
beam Pulse duration = 120 fs
Recording angle, θ = 70
degree
Period λ/(2sinθ) = 425 nm425 nm
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Sub-Rayleigh fringes ~/4 (M = 2)
Recording wavelength = 800 nm Two pulses with phase shiftPulse energy = 90 J per beam Pulse duration = 120 fsRecording angle, θ = 70 degree Fundamental period λ/(2sinθ) = 425 nmPeriod of written grating = 213 nm
213 nm
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Threefold enhanced resolution (M = 3)
Recording wavelength = 800 nm Three pulses with 2π/3 & 4π/3 phase shiftPulse energy = 80 J per beam Pulse duration = 120 fsRecording angle, θ = 8.9 degree Fundamental period λ/(2sinθ) = 2.6 mPeriod of written grating = 0.85 m
213 nm
2.6 m
1.67 m
0.8 m
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Non-sinusoidal fringes PMMA is a 3PA at 800 nm. (N=3)
Illumination with two pulses. (M=2)
If the phase shift of the second shot is
, where ,
the interference fringe is
Numerical calculation is similar to the experimental result.
This shows the possibility of non-sinusoidal fringe patterns.
33 ))cos(1(85.0))cos(1( KxKxI
10
7
141 nm
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Non-sinusoidal Patterns
Different field amplitudes on each shot can generate more general non-sinusoidal patterns.
M
m
Nmm KxAI
1
)]cos(1[
For example, if N = 3 , M = 3
A1 = 1 A2 = 0.75 A3 = 0.4
∆1 = 0∆2 = π/2∆3 = π
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Two Dimensional Patterns Method can be extended into two
dimensions using four recording beams.
M
mymx
Nmymy
Nmxmx KyAKxAthicknessPattern
1,
)]cos(1[)]cos(1[
For example,N=8, M=14
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Conclusion The possibility of the use of PMMA as a multi-photon
lithographic recording medium for the realization of quantum lithography.
Experimental demonstration of sub-Rayleigh resolution by means of the phase-shifted-grating method using a classical light source.
- writing fringes with a period of /4
Quantum lithography (as initially proposed by Prof. Dowling) has a good chance of becoming a reality.
Future work Higher enhanced resolution (M = 3 or more)
Build an entangled light source with the high gain optical parametric amplification.
Realization of the quantum lithography method.15/16
Acknowledgement
Supported by - the US Army Research Office through a MURI grant- the Post-doctoral Fellowship Program of Korea Science and Engineering Foundation (KOSEF) and Korea Research Foundation (KRF)
Dr. Samyon Papernov &
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Thank you for your attention!
http://www.optics.rochester.edu/~boyd
Two Dimensional Patterns Experimental 2-D pattern
1)Illuminate one shot, N = 3, M = 12)Rotate the sample3)Illuminate the second shot, N = 3, M = 1