EUV Interference Lithography in NewSUBARU

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1 EUV Interference Lithography in NewSUBARU Takeo Watanabe 1, Tae Geun Kim 2, Yasuyuki Fukushima 1, Noki Sakagami 1, Teruhiko Kimura 1, Yoshito Kamaji 1, Takafumi Iguchi 1, Yuuya Yamaguchi 1, Masaki Tada 1, Tetsuo Harada 1, Takayasu Mochizuki 1, and Hiroo Kinoshita 1 1 Laboratory of Advanced Science and Technology for Industry,University of Hyogo 2 Hanyang University takeo@lasti.u-hyogo.ac.jp

2 Outline 1. Introduction 2. Design concept of EUV-IL beamline 3. Setup and spatial coherence length measurement using double slit 4. Fabrication of transparent grating 5. Replicated resist patterns of L/S and dot patterns 6. Conclusion

3 Requirement of the resist line control in ITRS roadmap 2007 Line control size with nanometer level is required in 32 nm node below!! Line control size has to be smaller than the moleculer size of the base polymer!! Year DRAM HP (nm) Resist thickness (nm) LWR 3σ (nm) Sensitivity (EUV) mj/cm Outgassing (molecules/ cm 2 /s)

4 Necessity of EUV interference lithography Line control with sub nanometer is required!! Conventional EUV optics have aberration and flare. Low LWR of EUV resist is difficult to achieve. There is no aberration and no flare in EUV interference lithography. Thus, to achieve low LWR, EUV-IL is powerful for the evaluation of EUV resist in 22 nm node and below.

5 Principle of EUV-IL + 1st order light 0th order light Pattern is appeared!! EUV light ± 1st order light 0th order light + 1st order light Resist Wafer Grating Pattern Pitch = Grating Pitch / 2

6 Brilliance of long undulator and bending magnet Brilliance (photons/s/0.1%bw/mm 2 /mrad 2 ) Long Undulator Optical Klystron λ u =32cm / N=32 Short Undulator The sun 1st 1st 3rd 3rd 5th 7th 100meV 1 ev 10 ev 100 ev 1keV 10keV 100keV 1MeV 5th 5th/ 1.5GeV Banding magnet-1.5gev ε x =67nm ε y =6.7nm Banding magnet- 1.0GeV ε x =40nm ε y =4nm NewSUBARU I=220mA ΔE/E= ε x =40nm ε y =4nm SPring-8 BM Photon Energy (ev)

EUVL beamlines in NewSUBARU BL10 Bending Monochrometer Reflectometer Resist absorption & Transmittance 11m Long Undulator BL9 High power source and long coherence length PDI Experiment (Nikon &

7 EUVL beamlines in NewSUBARU BL10 Bending Monochrometer Reflectometer Resist absorption & Transmittance 11m Long Undulator BL9 High power source and long coherence length PDI Experiment (Nikon & Canon) Interference Lithography for 22nm and below Clean Room Mark 8 ICP Dry Etcher Nanometorics FT-IR Clean Draft Chamber SEM, AFM BL3 Bending Magnet Mask Inspection Resist characteristics Mask CD Measurement Contamination

8 Beamline setup for EUV-IL in NewSUBARU Light Source: 11-m Long Undulator Top View M0 Monochromator M4 M5 M6 M1 Slit M7 M8 Grating & wafer Pinhole (PDI system) Side View Focusing on the pinhole Beam size ~10μm (V) M0 M1 Slit M4 M5 M6 Monochromator M7 M8 Pinhole Grating & wafer 8

9 Light spectrum of the LU light source Electron storage current : 230 ma LU gap of 34.8 mm Photodiode Current (na) nA@7.24nm 398.5nA@13.38nm Wavelength (nm)

10 EUV-IL beamline in NewSUBARU EUV EUV-IL Exposure chamber

11 Experimental setup for the coherence measurement M6 concave mirror M7 concave mirror M8 plane mirror Shutter Double slit Slit Photodiode inside of Exp. Chamber Single slit : 3 mm (H) x 50 μm (V) 3 mm (H) x 25 μm (V) 3 mm (H) x 10 μm (V) Double slit : 2 mm (H) x 2 μm (V) Slit separation (μm) : 10, 20, 40, 80, 160, 320, 640, 1280 Pinhole~Double slit (DS) : L = 0.9 m DS~Exp. Chamber : L = 2.4 m 11

12 Calculation of the coherence length Fringe visibility (V) : Contrast = I I max max + I I min min I max I min : maximum PD current : minimu PD current Fringe visibility of Gaussian beam : R 2 c : coherence radius (R c =2L c ) d s d Contrast = exp( ) s : double slit separation 2 2R l c c : spatial coherence at the DBL slit position Spatial coherence is defined: Contrast Spatial coherence at double slit position: = exp( 1/ 8) = l c = d s Spatial coherence length at transmission grating: L = ( DBL Grating) /( SLIT DBL) l = 2.4m / 0. 9m l c c c 0.88

13 Examples of light intensity measurement at the grating position Slit width 25 μm Double slit separation 320 μm Slit width 10 μm Double slit separation 640 μm Photodiode Current (A) 7.00E E E E E E E E E Position (μm) Photodiode Current (A) 4.00E E E E E E E E E E Position (μm)

14 Results of the spatial coherence length measurement Normalized Contrast μm-width slit 10 μm-width slit LU gap: 34.8 mm Storage ring current: 230 ma Distance slit-ds: 0.9 m Distance slit-grating: 2.4 m Double slit separation distance (μm) Position 25 μm slit 10 μm slit DS 204 μm 440 μm Grating 544 μm 1173 μm

15 EUV-IL exposure tool in NewSUBARU Grating stage λ= 13.5 nm Wafer stage

16 Replicated L/S pattern by EUV interference lithography Resist pattern of 25 nm hp (34 nm line and 16 nm space) Resist: ZEP520A Resist thickness: 50 nm Dot dense pattern Dot pattern width 71 nm ZEP520A 50 nm t

17 Fabrication process of novel transmission grating 40 nm HP and 30 nm HP grating patterns require high etching durability. Si3N4 Si Si3N4 Si3N4 Coated on Si substrate Deposition of TaN and SiO2 Coating ZEP520A resist Electron beam exposure Dry etching by Cl2 gas Dry etching by CF4 gas Dry etching by CF4 gas Wet etching by KOHaq Completion

18 Fabricated novel transmission grating 2mm 2mm 20mm 20mm The detail of the novel transmission grating and the exposure results using this novel grating will be presented at EUVL symposium 2009 and MNC2009.

19 Conclusions 1. EUV-IL beamline with 11-m long undulator was constructed at the BL9 beamline in NewSUBARU. 2. It was confirmed that spatial coherence length of more than 1.0 mm by Young s double slit experiment nm HP dense resist pattern and 71-nm-width dot dense pattern were replicated using EUV-IL. 4. A two-window transparent grating was succeeded to fabricated in our lab.

20 Acknowledgement I would like to thank to each person who support our experiment.

Recent Activities of the Actinic Mask Inspection using the EUV microscope at Center for EUVL

Recent Activities of the Actinic Mask Inspection using the EUV microscope at Center for EUVL Takeo Watanabe, Tetsuo Harada, and Hiroo Kinoshita Center for EUVL, University of Hyogo Outline 1) EUV actinic