1. Next-generation multi-wavelength
lithography: survey and roadmap
John S. Petersen, Periodic Structures, Inc.
john@periodicstructures.com
512.751.6171
John T. Fourkas, Univ. of Maryland
Steven R. J. Brueck, The Univ. of New Mexico
Dave Markle, Periodic Structures, Inc.
Rudi Hendel, Periodic Structures, Inc.
Paper 9052-6 Time: 11:40 AM - 12:00 PM

2. Outline and Comments
• Super-resolution with Multi-wavelength lithography (MWL)
– Principles: Improve resolution by trimming an actinic image using a deactivating λ
– Resist Background: For non-SC applications resolution to 9 nm using visible λ
• Semiconductor Lithography
– Possible Tool Solutions: Modified scanner, Interference litho, Direct-Write
– Theoretical Resolution < 10 nm and pitch < 20 nm
– Estimated Throughput 30 wafers per hour for grid based designs, 7.8 for arbitrary
• Status
– Thick to thin resist challenges ITX, DETC and MGCB
– Resist screening test apparatus
– CINT transitive absorption spectroscopy
• Conclusions
– The technique holds great promise and requires industrial support to make it real
– Resist requirements
• 2-color resists will work for small features and large pitches
• 3-color resists provide the best avenue to small pitch.
– Material development for SC lithography is required.
Paper 9052-6 Next-generation multi-wavelength lithography 2

3. Motivation for a New Lithography
• Money
– EUV and 193i multi-patterning is prohibitive except for HVM
of leading edge devices.
– Scalable maskless multi-wavelength litho enables the rest.
• Enables
– Rapid prototyping and limited run products using ODW
– EUV mask production
– Imprint Templates
– Arbitrary and gridded 10 nm DSA piloting structures
• Coulomb
– Replaces e-beam in DW of masks, templates and wafers
Paper 9052-6 Next-generation multi-wavelength lithography 3

4. InSTED Lithography
• Interlace Activation
(λA) and
Deactivation (λD)
interfering beams
• Trims the beam so
the resist near the
image is not exposed
allowing placement
of another line
beside it.
107 nm @ 0.4 Intensity λA=405nm λD=532nm; before STED 174 nm
Paper 9052-6 Next-generation multi-wavelength lithography 4
Relative Intensity
Lateral Position (nm)

5. InSTED Lithography Examples
20 nm on 300 nm Pitch
@ 0.4 Intensity λA=405nm
λD=532nm (50X Intensity)
107 nm on 300 nm Pitch
@ 0.4 Intensity λA=405nm
λD=532nm (1.2X Intensity)
Before STED trimming: 174 nm @ 0.4 Intensity
Paper 9052-6 Next-generation multi-wavelength lithography 5
Relative Intensity
Lateral Position (nm)
Relative Intensity
Lateral Position (nm)

6. InSTED Lithography
20 nm on 40 nm Pitch @ 0.4 Intensity λA=405nm λD=532nm
1 1 12 2 23 3 34 4 4
Paper 9052-6 Next-generation multi-wavelength lithography 9

7. InSTED Lithography
Interference STimulated Emission-Depletion Lithography
Absorption 10-15 s
2-photon separation <10-18 s
Fluorescence 10-9 - 10-7 s
Non-Radiative 10-15 - 10-12 s
Vibrational Relaxation 10-14 - 10-11 s
Inter-System Crossing 10-8 - 10-3 s
Ultra-Fast Chemical Rx’s 10-6 - 10-3 s
Phosphorescence 10-4 - 10-1 s
Fast Chemical Reactions 10-6 - 10-3 s
ESA
STED
Fluorescence
Non-RadiativeDecay
TTA
T1
Tn
S1
Sn
S0
S0
*
S1
*
Sn
*
Tn
*
1-PhotonAbsorption
2-PhotonAbsorption
Use STED or STED-like to
selectively shutdown
further reaction to trim
the aerial image.
Photochemical reaction time scales (Ref: Modern Molecular Photochemistry by
Nicholas J. Turro, University Science Books, Sausalito, CA, copyright 1991, p. 5
Paper 9052-6 Next-generation multi-wavelength lithography 10

8. Possible Photo Pathways
2/23/2014
IEUVI Resist TWG Meeting
Periodic Structures, Inc.
11

9. Spectra and Excitation-Depletion
Absorbance
Fluorescence
Phosphorescence
STED 2-Photon
1-Photon
RelativeSpectralUnits
Wavelength (nm)
300 810532400
12
Paper 9052-6 Next-generation multi-wavelength lithography 12

10. Photo-shutter MGCB Demo
Courtesy of Zuleykhan Tomova, Fourkas Group, UMD 2014
Activation
+
Deactivation
Activation
Activation
Paper 9052-6 Next-generation multi-wavelength lithography 13

11. Thin Resist Result
NA=1.45
Resolution Pitch Limit: 673-551 nm
Achieved 400 nm w/pattern collapseFourkas Group Set up
Paper 9052-6 Next-generation multi-wavelength lithography 14

12. Mechanisms Beyond STED for Lithography
• Stimulated Emission-Depletion (STED): None
confirmed for lithography
• Photo reversible solvated electrons (Fourkas:
Malachite Green using RAPID)) ????
• Triplet-Triplet Absorption (Wegener, also Harke: ITX,
DETC research, thought it was STED at first) ????
• Photon induced inhibition of polymerization (PIP)
McCleod, and Gu
• Photo chromic over layers (PCO) (Menon using
AMOL)
• Multi-wavelength Molecular switches (PSI proposes)
Paper 9052-6 Next-generation multi-wavelength lithography 15

13. Photon induced Inhibition of Polymerization
9 nm resolution shown in “E” but consumes reactants and won’t cycle without dose
correction.
Paper 9052-6 Next-generation multi-wavelength lithography 16
Z. Gan, Y. Cao, R. A. Evans and M. Gu, Nat. Commun., 2013, 4, 2061
Ugly
but
9 nm

14. Simple 2-Color Resist
Paper 9052-6
Next-generation multi-wavelength
lithography
17

15. 0
2E+13
4E+13
6E+13
8E+13
1E+14
1.2E+14
1.4E+14
1.6E+14
1.8E+14
2E+14
0 2 4 6 8 10 12 14 16
NumberofMolecules/Photons/cm2
Exposure Time (micro-seconds)
2- Color Model
Extended Inhibition, R=10:1, 12.5 μs exposure,
T=5E-5
Remaining Excited Atoms
Exposed Atoms
Exposure Flux
Exposed Flux
Remaining Excited Species
Irreversible Species
Paper 9052-6 Next-generation multi-wavelength lithography 18

16. 0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
50.00 60.00 70.00 80.00 90.00 100.00 110.00 120.00 130.00 140.00
RelativeExposure
Lateral position (nm)
Comparison of Three Resist Exposure Models
2-Color Model
Simple Model
3-color model
Paper 9052-6 Next-generation multi-wavelength lithography 19

17. Molecular Switch
Write Mask → Image Mask → Erase Mask (Repeat)
• Photo chromic has limited potential:
– Absorbance shutter
– May work but requires a multilayer process
– Challenge partial exposure in undesired areas limits
pixel size and pitch resolution
• Photochemical (believe this is the best option)
– OFF is no actinic functionality: OFF is OFF & ON is ON
– Single image layer capable
– Rich legacy in the development of switches for
storage and molecular electronics
Paper 9052-6 Next-generation multi-wavelength lithography 20

18. Super-resolution Lithography System Schematic
Camera
Telecentric
Relay
D
M
D B B R
Beam-
splitter
Objective
Light Pipe
Frustrated Prism
Dose
Detector
Stage
Grating
Phase
Shifter
Laser Diodes
Inhibition
Laser
Paper 9052-6 Next-generation multi-wavelength lithography 21
US8642232 B2

19. Pixels Projected to the Wafer
Paper 9052-6 Next-generation multi-wavelength lithography 22
US8642232 B2
Deactivation Pattern Activation Pattern
Superimposed at the wafer

20. Lithography projection using InSTED
J. T. Fourkas and J. S. Petersen, Phys. Chem. Chem. Phys., (to be published 2014).
Paper 9052-6 Next-generation multi-wavelength lithography 23

21. Throughput varies with the type of Pattern
and the Line Edge Resolution
Pattern Type
Continuous
Lines
Broken
Lines
Arbitrary
Pattern
Assumptions: 2560 by 1600 pixel DMD 20 kHz frame rate,
7.8 μm DMD pixel spacing 20 nm image pixel
50 mm by 75 mm footprint, 0.5 m/s maximum scan rate
266 nm interference wavelength 0.95 NA
Period = λ/2NA = 140 nm Magnification = 7.8/.14 = 55.7
Acceleration = 1g
Paper 9052-6 Next-generation multi-wavelength lithography 24
Line Edge
Placement
Time/Footprint
20 nm 35.3 s (102/hr)
117.5 s (30.6/hr)20 nm
2.5 nm 460.2 s (7.82/hr)

22. Throughput Estimates for a Fully Populated
Super-Resolution System having 20nm Pixel
Size and 2.5 nm Edge Position Grid
DMD No of Pixels Frame Rate Pixel size Time/Footprint Throughput*
Generation Million kHz (microns) seconds Substrates/hr
0 4.096 20 7.8 458.414 7.604
1 8.192 30 7.8 153.764 21.332
2 16.384 40 5 58.522 48.965
3 32.768 50 5 24.544 91.039
* Includes 15 second substrate change time
Paper 9052-6 Next-generation multi-wavelength lithography 25

23. Cost versus Throughput Estimates for a
20 nm Super-Resolution System Using
3rd Generation DMD Technology
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25
Throughput(300mmWafers/hr)
Cost ($Millions)
X 1-Column
X 6-Columns
X 20-Columns
Paper 9052-6 Next-generation multi-wavelength lithography 26

24. Resist Technical Requirements
Challenge: Has to work as a resist
– Fast with good LWR
– No pattern collapse, Swelling mitigated, Good etch selectivity & I2
– Minimal diffusion of active components
• Has to act as an optical switch need to recycle hundreds of times
with no discernible functional drift
– 50 µs full process cycle which is the max frame rate of DMD
– Correctable and accountable reactant consumption
– Restrict unwanted reaction pathways
– Thermal effects during exposure (chemistry and wafer-scale)
– Sublimation and outgassing
– 3-wavelength (make mask, expose mask, erase mask) is best.
• Unwanted quenching controlled
– Oxygen effect that grows as resist thins
Paper 9052-6 Next-generation multi-wavelength lithography 27

25. PSI Enables Material Development
• Develop and supply tools for:
– Material R & D
– Lithography test
– Lab-2-fab imaging tools
• Litho
• Inspection
• PSI Connections and Capability
– Fourkas Group at UMD
– Resist screening lab and equipment at UNM
– CINT transient absorption measurement in film
From this meeting we propose creating an effort to develop
a commercially available multi-color resist !!!
Paper 9052-6 Next-generation multi-wavelength lithography 28

26. InSTED Apparatus
Activation Lasers
Delivery Through
Beam Splitter
Activation Lasers Activation Lasers
Delivery Through Beam
Splitter and
Deactivation via Split
and Angled Mirrors
405 nm Solid-State Diode Laser (Multi-mode)
364 nm Argon Ion Laser Single Mode
Paper 9052-6 Next-generation multi-wavelength lithography 29

27. Thank You
Work supported by NSF Grant: IIP-1318211

28. 0
0.2
0.4
0.6
0.8
1
1.2
-0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4
ExposureDose
Image Position (Microns)
Exposure Dose Profile for Various
Inhibition to Exposure Intensity Ratios
1
2
4
8
16
32

29. Fourkas: RAPID1
800 nm CW
800 nm
pulsed
Intiation(solvated)ePI](solvated)ePI[PI diffusionhνexpose
 →+ →+ → −+−+
hνdeactivate
1Resolution augmentation through photo-induced deactivation (RAPID) lithography
L. Li, R. R. Gattass, E. Gershgoren, H. Hwang, John T. Fourkas, "Achieving l/20 Resolution by One-Color Initiation and
Deactivation of Polymerization", Science, 324, pp. 910-913 (15 May 2009).
Vertical Imaging forms ridges in the tower structure.
USA Patent: 8432533
Paper 9052-6 Next-generation multi-wavelength lithography 32

30. J. Fischer, G. von Freymann, and M. Wegener, “The materials challenge in diffraction-unlimited direct-laser writing optical lithography,”
Adv. Mater. 22, 3578–3582 (2010).
Fischer, Freyman and Wegener:
Evidence for Trimming but not STED
STED
Not STED
2/23/2014
IEUVI Resist TWG Meeting
Periodic Structures, Inc.
33

31. Photon induced Inhibition of Polymerization
• Three basic components
– Photoinitiator
• 2,5-bis(p-dimethylaminocinn amylidene)-cyclopentanone
– Polymerization photo inhibitor
• tetraethylthiuram disulphide
– Monomer matrix
• Capable of high resolution but consumes
TED
BDCC
Z. Gan, Y. Cao, R. A. Evans and M. Gu, Nat. Commun., 2013, 4, 2061
Paper 9052-6 Next-generation multi-wavelength lithography 34

32. Photon induced Inhibition of Polymerization
Z. Gan, Y. Cao, R. A. Evans and M. Gu, Nat. Commun., 2013, 4, 2061
52 nm Pitch is good but reactant consumption limits ability to make smaller pitches
Paper 9052-6 Next-generation multi-wavelength lithography 35

33. Menon: AMOL
R. Menon, H-Y Tsai and S. W. Thomas III, "Far-Field Generation of Localized Light Fields using Absorbance Modulation",
PRL 98, 043905 (2007).
Control
Paper 9052-6 Next-generation multi-wavelength lithography 36

34. References
• S. W. Hell and J. Wichmann, Opt. Lett., 1994, 19, 780-782.
• J. T. Fourkas and J. S. Petersen, Phys. Chem. Chem. Phys., (to be published 2014).
• K. Berggren, A. Bard, J. Wilbur, J. Gillaspy, A. Helg, J. McClelland, S. Rolston, W. Phillips, M. Prentiss and G.
Whitesides, Science, 1995, 269, 1255-1257.
• L. J. Li, R. R. Gattass, E. Gershgoren, H. Hwang and J. T. Fourkas, Science, 2009, 324, 910-913.
• T. F. Scott, B. A. Kowalski, A. C. Sullivan, C. N. Bowman and R. R. McLeod, Science, 2009, 324, 913-917.
• T. L. Andrew, H. Y. Tsai and R. Menon, Science, 2009, 324, 917-921.
• J. T. Fourkas, J. Phys. Chem. Lett., 2010, 1, 1221-1227.
• J. Fischer, G. von Freymann and M. Wegener, Adv. Mater., 2010, 22, 3578-3582.
• J. Fischer and M. Wegener, Opt. Mater. Expr., 2011, 1, 614-624.
• B. Harke, P. Bianchini, F. Brandi and A. Diaspro, Chemphyschem, 2012, 13, 1429-1434.
• B. Harke, W. Dallari, G. Grancini, D. Fazzi, F. Brandi, A. Petrozza and A. Diaspro, Adv. Mater., 2013, 25, 904-909.
• J. Fischer and M. Wegener, Laser Photon. Rev., 2013, 7, 22-44.
• M. P. Stocker, L. Li, R. R. Gattass and J. T. Fourkas, Nat. Chem., 2011, 3, 223-227.
• Y. Y. Cao, Z. S. Gan, B. H. Jia, R. A. Evans and M. Gu, Opt. Expr., 2011, 19, 19486-19494.
• Z. Gan, Y. Cao, R. A. Evans and M. Gu, Nat. Commun., 2013, 4, 2061.
• Z. S. Gan, Y. Y. Cao, B. H. Jia and M. Gu, Opt. Expr., 2012, 20, 16871-16879
Paper 9052-6 Next-generation multi-wavelength lithography 37