BeamBeam ApplicationApplication toto NanotechnologyNanotechnology basedbased onon SubpicosecondSubpicosecond PulsePulse RadiolysisRadiolysis

Seiichi Tagawa The Institute of Scientific and Industrial Research, Osaka University 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan AcknowledgmentAcknowledgment

• Coworkers • T. Kozawa • A. Saeki • H. Yamamoto • K. Okamoto • Prof. S. Seki • Tsukuda New Sub-picosecond Pulse Radiolysis System

Klystron(replaced for stabilization) Light Detection Highly stabilized SHPB amplifier (replaced for stabilization) system coolant Time jitter e-Gun Magnetic pulse compensation system compression system

Master Oscillator L-band Linac Optical delay Linac Control panel (replaced for sophisticated Trigger data logging) Generator With Synch. Circuit New laser system (300nm-10µm) Pulse generator Femtosecond laser system To other devices such as in clean room oscilloscope and so on. New Femtosecond Pulse Radiolysis System

Klystron Light detection system Laser Photocathode RF-Gun Time jitter S-band Linac Magnetic pulse compensation system compression system

Master Oscillator Optical delay Linac control panel

Trigger Generator With Synch. Circuit

Pulse generator To other devices such as oscilloscope and so on. Femtosecond laser system (300nm-10µm) Co-operation of Our Research Groups in The Institute of Scientific and Industrial Research, Osaka University Department of Beam Science & Technology ( S. Tagawa, Y.Yamamoto, K.Kobayashi, A.Saeki)

Radiation Laboratory Department of Beam 20 Members Processing for Nanotechnology (S.Tagawa, Y.Yamamoto, (S.Tagawa, T.Kozawa, S.Seki) T.Kozawa, S.Seki, K.Kobayashi, A.Saeki from our group) Nanofoundry Y.Matsui and K.Okamoto in Tight Co-operation with S.Tagawa, T.Kozawa, S.Seki

21st Century COE Program Chairman of 21st Century COE Program Committee（S. Tagawa） 5 Research Groups:IT Nanotechnology G (Group Leader：S.Tagawa) Nanofabrication Research of Our Group Based on Radiation Chemistry Bottom-up Type Top-down Type Nanotechnology Nanotechnology Material Design and synthesis Nanolithographies

Beam Science Research Consortiums Combination of and Technology SELETE(ASUKA) : Two Nanotechnologies EB,F2,Immersion ArF Mass-production Type ASET ：EUV Nanofabrication Several Companies Nanoscience and Next Generation Lithograpy Nanotechnology and Future Lithographies <30nm (So-called Non-Mass Production Type) （CD control <2nm） (So-called Mass Production Type) Nanobeam Processes and Development of Nanomaterials

Ultra-fine Electron Beam atternP Use of Single Charged Particle Events Super Fine Pattern Formation 500 nm by the design of chemical e- 500 nm reaction, molecular structure Nano-fluorescent Light E

Single Ion Track e-

Field Emitter NanoNano MaterialsMaterials C60 etc., 1985 Carbon Nanotubes 1991 Iijima

Size Control, Spatial Distribution, Structure, etc.

RadiationRadiation InducedInduced ReactionsReactions inin PolymersPolymers InducedInduced IonsIons

The size of the field depends on Reactive intermediates Density Stability Linear energy transfer: LET Structure of a molecule (Mw, Stiffness, etc.)

Very good size control and mass production IonIon TrackTrack StructureStructure inin PolysilanesPolysilanes

zPolysilanes »Silicon Analog of Polyethylene »1-D Analog of Crystalline Si zProperties zElectroluminescence zPhotoconductivity z1-D Quantum wires zRadiation Sensitive UniformityUniformity ofof NanoNano--WiresWires

Figure. A SEM image of rod-like nano-wires on a Si substrate. The nano-wires were formed by the 450 MeV 128 23+ 12 2 Xe irradiation to a PS3 thin film (200 nm thick) at 1.6 x 10 ions/cm . The film was developed by hexane, and heated up to 523 K for 0.5 h after irradiation. UniformUniform FormationFormation ofof NanowiresNanowires

(a)(a) 200 nm (b)(b) 500 nm (c)(c) 1.0 µm

Figure. AFM images of nano-wires on a Si substrate with a variety of special resolutions. The nano-wires were formed by the 450 MeV 128Xe23+ irradiation to a PS1 thin film (0.40 mm thick) at 1.7 x 1010 ions/cm2. ns pulse radiolysis

LINAC (L-band electron linear accelerator) 28MeV 8nsc Gun

Monochromator Si / InGaAs Detector

Cryostat Oxford Instruments Optistat DN Sample Cell Signal Temperature Liq. Nitrogen Control Wavelength Range ２５０ｎｍ～２１００ｎ Transient Digitizer Xe Pulse Lamp Lens SCD 1000

BeamCharge Trig.

Beam Catcher

Trig.

Sync. Circuit ns pulse radiolysis

A kinetic trace in wide dynamic range can be measured by one pulse irradiation A A ∆ ∆ A A ∆ ∆ A A ∆ ∆ A A ∆ ∆ A A ∆ ∆ A 0 A 200 ∆ ∆ A 0 Time (µsec) A 82 ∆ ∆ 0 Time (µsec) 41 0 Time (µsec) 20 0 Time (µsec) 8 0 Time (µsec) 4 0 Time (µsec) 2 -. Time (µsec) (SCN)2 In-situ TRMC-TAS

In-situ TRMC-TAS Materials (Film)

Dissolved in THF and Streak CCD drop-casted on quartz camera substrate.

Freq. counter

Nd:YAG laser Gunn Div. Div. Att. Circ. (532, 355nm) n

Amp. RR-P3HT NC CN Att. P.S. Mixer NC CN Xe Lamp Freq. Met. Att. TCNE

AFC unit Power Supply Oscilloscope History of pulse radiolysis at ISIR

ns system ps system (stroboscopic)

UV, Vis 1994 Laser-linac synchronized, 1995 NIR, 1995 Vis, 1998 Low-temp, NIR, Vis, 1997 Pulse compression, 1998 IR, 1998 Jitter compensation, 1999 UV, Vis, ns-ms, 2001 Improvement of S/N ratio, 2001

IR NIR Vis UV ps ns µs ms Nanobeam Processes and Development of Nanomaterials

Ultra-fine Electron Beams

Super Fine Pattern Use of Single Charged Particle Events Formation by the design of chemical e- reaction, molecular structure 500 nm Nano-fluorescent Light

E

Single Ion Track e-

Field Emitter Miniaturization trends of DRAM pattern size and development of optical lithographic tools. DRAM capacity is given in bits.

Sub-Half-Micron Lithography for ULSIs edited by K. Suzuki, S. Matsui and Y. Ochiai First Year of IC Production (year) Dram Half 2004 2007 2010 2013 2016 Pitch (nm) 193 nm PEL:Proximity Electron Lithography 65 157 nm EPL:Electron Projection Lithography 193 nm immersion Optical EUV:Extreme Ultraviolet EPL, PEL ML2:Maskless Lithography

157 nm DWEB 45 193 nm immersion ML2 EPL, PEL Post-optical

157 nm immersion 32 EUV EPL ML2

*ITRS2003 EUV EPL 22 ML2 Imprint lithography *ITRS2003 What limits the resolution of EB lithography The limit of the resolution of the high sensitive EB resists is key problem for the future lithographies (both EB and EUV lithograph). It is also essence for the development of nanotechnology. Effects of developer, Beam size(< 1 nm) Development conditions

Intermolecular forces Polymer size effects during development Cluster size effects

Acid diffusion Forward- and back- Reaction scattered electrons mechanisms EB can be focused less than 1 nm. However, technical barriers exist around 30-50 nm for mass production type resist pattern. Why? More important problem is critical dimension (CD) and Line edge roughness (LER). Chemically amplified resist

Generation of acid by exposure hν、radiation + - hν + - Ph3S X レジスト H X Pattern formation utilizing polarity change by deprotection reaction Solubility Change H H H H CH3 + CC CC + CO2 + CCH3 n n H H CH3 CH3 OCOCCH3 OH O CH3 Acid catalytic reaction H+ High Sensitivity CH3 + H + C CH2 CH3

×Polmerization, graft polmerization, and others Acid generation mechanism – Ionization channel

Electron beam, X-ray, EUV

Base polymer Ionization Proton generation Acid generator Counter anion Proton Proton transfer Electron Acid generation

Acid diffusion Reaction control in nanospace --Time space translation A. Saeki et al. Jpn. J. Appl. Phys. 41 (2002) 4213. It is essential to minimize the displacement between energy deposition point and reaction point. Time-space translation

0.06 Experimental data Translation of picosecond temporal Simulation 0.05 data to nanometer spatial data

0.04 （So far, available only at ISIR）

0.03

0.02

0.01 r0 = 6.6 nm Optical density 0 D = 6.4 x 10-4cm2/s e = 2.012 -0.01 -50 0 50 100 150 200 250 300 350 Time (ps) After exposure to EB 0 ps 30 ps Experimental data obtained in 100 ps the femtosecond pulse density Probability

radiolysis and simulation 0 5 10 15 20 25 30 Spatial separation between electron and The distance between cation radical and electron [nm] cation radical causes the displacement between energy deposition point and Change of distance between electron and reaction point. For the nanotechnology, it cation radical generated by electron beam is essential to decrease the displacement. irradiation. Electron dynamics in early processes of radiation chemistry Electron with excess energy Thermalization Ionization - - Diffusion + Coulomb Force Radical Cation Electron Geminate Ion Pair

Smoluchowski equation Initial distribution function ∂w  1  1  r    f (r,r0 ) = exp−  = D∇∇w + w ∇V  r  r  ∂t  kBT  0  0  w : Probability density of electrons r : Distance between radical cation kB : Boltzmann constant and electron V : Coulomb potential r0 : Initial separation distance T : Absolute temperature on average D : Sum of diffusion coefficient n-Dodecane Benzene

0.20 0.3

0.15 0.2 0ps 0ps Electron Electron 0.10 30ps 0.1 3ps 0.05 100ps 10ps 300ps 30ps 100ps 0.00 0 Survival probability (/nm) Survival probability (/nm) Survival probability 0 5 10 15 20 25 30 0 5 10 15 20 25 30 Cation-Electron Distance [nm] Cation Cation Cation-Electron Distance [nm] Distribution of Electron Distribution of Electron

r0 = 6.6 nm r0 = 3.2 nm D = 6.4 x 10-4cm2/s D = 2.8 x 10-3cm2/s ε = 2.012 ε = 2.284 Base Polymers for Lithographies

g / i KrF ArF F2

Aromatic ｒing Alicyclic groups Cyclic olefine polymer F polymer

OOOO R R' OO

O Rf OO Ploy(methacrylate) R O O Ploy(methacrylate) OO OH OH O Poly(acrylate OO -hydroxystyrene) CH 2

CH 3

O ｌ ｒ F3CO O Nobo ak esin O CF 3 R Ploy(norbornene Ploy(norbornene - maleic anhydride) - maleic anhydride) O OH R Ploy(p-hydroxystyrene)

O O R Ploy(norbornene) Acid generation mechanism – Ionization channel

Electron beam, X-ray, EUV

Base polymer Ionization Proton generation Acid generator Counter anion Proton Proton transfer Electron Acid generation

Acid diffusion Formulation The reaction of acid generators with electrons: ∂w = −kCw ∂t Effective reaction radius of acid generators: k = 4πRD Electron dynamics in resist materials: ∂w  1  = ∇∇w + w ∇V  − 4πRCw ∂Dt  k BT  w : probability density of electrons k : rate constant of reaction of acid generator with electrons C : concentration of acid generators R : effective reaction radius Effective reaction radii of acid generators Acid generator k (M-1s-1) R (nm) Acid generator k (M-1s-1) R (nm)

CCl3 N I CF SO 10 Cl C N 10 3 3 2.4 x 10 2.1 3 2.2 x 10 1.9 N CCl3 CCl3 N S CF SO 3 3 2.7 x 1010 2.4 N 2.5 x 1010 2.2 N CCl3

O O 10 SS 10 S SbF6 2.5 x 10 2.2 1.1 x 10 0.96 OO

O NO2 S 10 CH OSO CH 10 1.9 x 10 1.7 2 2 3 2.2 x 10 1.9 CF SO 3 3 NO2 CH3 CF3SO3 S 1.6 x 1010 1.4 O R : Effective reaction radius of acid generators k = 4πRD D : Diffusion coefficient of solvated electrons in methanol (1.5 x 10-9 m2s-1) k : Rate constant of reaction of acid generators with solvated electron in methanol

) (/nm density Probability ) (/nm density Probability

3 3

) )

0.06 0.0015

m

m 0 0

n n

(

(

e e

c

c 5 5

n n

a

a

t t

s s

i i 0 0

D D 0.06 0.0015 -5 -5 -10 -10 10 10 5 5 ) ) m m 0

n 0 n 0 0 ( ( e e c c n n a

a -5 -5 t t is is = 0.05 = 0.005 D D 2 2 0 0 -10 -10

Dt/r Dt/r

) (/nm density Probability

3

0.25 )

0 m

n

(

e

5 c

n

a

t

s

0 i D 0.25 -5 -10 10

5 ) m

n 0 0 ( e c

Distribution change of electrons around ionization point n a -5 t is

= 0.0005 D 2 0 -10 The distribution of probability density of density The distribution of probability the x-yin electrons The coordination of plane. ionization point is the origin. Dt/r

) (/nm density Probability

) (/nm density Probability 3

3

)

0.025 )

0.0075

m

m 0 0

n n

(

(

e e

c

c 5 5

n n

a

a

t t

s s

i i 0 0

D D 0.025 -5 -5 0.04 -10 -10 10 10 5 5 ) ) m m n n 0 0 0 0 ( ( e e c c n n a

a -5 -5 t t is is = 0.05 = 0.005 D D 2 2 0 0 -10 -10

Dt/r Dt/r

) (/nm density Probability 3

0.04

)

0 m

n

(

e

5 c

n

a

t

s

0 i D 0.0075 -5 -10 10

5 ) m n 0 0 ( e c n a -5

t . is

= 0.0005 D 2 0 -10 The distribution of probability density Counter anion distribution around ionization point counter anions in the x-yThe plane. coordination of ionization point is the origin Dt/r Conclusion 2

The elucidation of the reaction mechanisms of chemically amplified resists is very important in the development of the resists with at least both high sensitivity and high space resolution. Our findings were integrated to a simulation model. This model is applicable to exposure souses whish have higher energy than ionization potential of resist materials. The probability density of acid distribution around ionization point was simulated with a typical parameter set.