Development of ultra-fine structure t metrology system using coherent EUV source

Size: px

Start display at page:

Download "Development of ultra-fine structure t metrology system using coherent EUV source"

Dayna Crawford
5 years ago
Views:

1 2009 International Workshop On EUV Lithography, July 13-17,2009 Development of ultra-fine structure t metrology system using coherent EUV source University of Hyogo 1, Hiroo Kinoshita 1,3, Tetuo Harada 1,3, and Takeo Watanabe 1,3 Riken 2 Yutaka Nagata 2,3, JST CREST 3

2 Technical issues of EUVL Absorber pattern Substrate Mo/Si ML Mo 3nm Si 4nm Focus area of EUVL on 2008 EUVL Symposium Defect free mask is the critical issue of the EUV Lithography. Amplitude Development of an actinic mask Phase inspection tool Glass Glass Target:<25 nm

mirror (10~200X) CCD camera (6 µm/pixel)

3 Technical background:actinic Mask Inspection System using EUV microscope has been developed. SR (EUV) 13.5nm Turning mirror Elbow pattern Schwarzschild objective (NA 0.3, 30X) Electromagnetic lens Turning mirror (10~200X) CCD camera (6 µm/pixel) Photocathode MCP (CsI) X-ray zooming tube Dot pattern Mask Line phase defect Dot phase defect Resolution limit estimated to be 50 nm. A new system with higher NA is required, but

4 Coherent Scattering EUV Microscope (CSM) CSM at New SUBARU BL-3 Mo/Si Concave EUV CCD m 2048pxl Pinhole Mo/Si Flat SR EUVL Mask 6 deg 50 mm White SR beam was monochromatized with Mo/Si MLs and a Zr filter. Spatial coherence is obtained through pinhole Φ5 m diameter. NA is defined by the size of CCD and the distance between CCD and mask. To clarify the shadowing effect, Incident angle was set to 6 deg.

$Principle of new system Imaging theory of Fraunhofer diffraction Pupil plane Imaging plane -1order 0th +1order Sample Fourier Transforom Inverse Fourier Transform X-Y Stage$

5 Principle of new system Imaging theory of Fraunhofer diffraction Pupil plane Imaging plane -1order 0th +1order Sample Fourier Transforom Inverse Fourier Transform X-Y Stage -2 order -1 order 0th +1 order +2 order Sample X-ray CCD Cohertnt light source Computer This lensless method is Discovery Science and technology Based on optical principal.

6 Advantages of this system 1)Resolution is equivalent to the wavelength to be used. 2)Since objective and focus detector are not required, system can be constructed at a low cost. 3)Footprint is small by using a HHG Laser system. 4)Inspection time will be improved by the development of most suitable algorism. Ultimate inspection technology by light

Image Reconstruction Algorithm The phase information is

$Algorithm Known in the X-ray diffraction microscopy$ Phase Reconstruction with iteration of Fourier transform (FT)

Over Sampling (Restriction) Frequency space 周波数空間 CSM Data

7 Image Reconstruction Algorithm The phase information is essential for image reconstruction Hybrid Input Output(HIO) Algorithm Known in the X-ray diffraction microscopy Restriction: recorded unexposed area information must be ZERO Phase Reconstruction with iteration of Fourier transform (FT) and Invert FT. Over Sampling (Restriction) Frequency space 周波数空間 CSM Data Phase Invert FT Real space EUV Exposure Area Revise Amplitude Phase Fourier Transform The information of unexposed area must be ZERO.

8 Observation Result (1) CSM observation result of our samples, and reconstructed image with the CCD data CCD Data Reconstructed image hp200 nm Line & Space time 12 min 5 m Magnify hp100 nm Line & Space time 8 min Magnify L:S ~ 1:1 Sample

9 Observation Result (2) hp300 nm, Line & Space, 10 min Reconstructed image SEM image Magnify hp 400 nm, Hole, 10 min Reconstructed image SEM image Magnify A Line width of 300 nm hp was well corresponding with a SEM image. A hole pattern of 400 nm hp was reconstructed.

Amplitude 512 512 pixel 128 pixel 1 2 5 10 20

10 Simulation of the HIO Algorithm Original Image Original and Exposed Area Calculated FT Amplitude pixel 128 pixel (Magnify) Iteration numbe er (16 s)

11 Example of reconstructed images 132nm Gate 120nm Contact 132nm Bit Line

12 Reconstructed image of mask Defect on mask 107nm 107nm SEM image CSM Image By Dong Gun Lee

$I -2 I 2 Fraunhofer Diffraction$ I = I 0 Sinβ β 2 SinNα 2 α 1 0.

13 Critical dimension measurement method 測定値 I 0 Measurement Normalize I n I -1 I 1 I 0ex I I -2 I 2 Fraunhofer Diffraction I = I 0 Sinβ β 2 SinNα 2 α Theoretical value I 0.6 = kasinθ = kbsinθ n α 2, β 2 I 0th 0.4 Calculate K=wave number a=pitch b=cd 0.2 ΔI Verification Fitting Fitting Curve n

14 Comparison between CSM and CD-SEM 40 CD (nm) 40 CD (nm) Y (mm) Y (mm) X (mm) CSM uniformity it map 3σ=4.7 nm Pitch 256nm X (mm) SEM uniformity it map 3σ=4.4 nm 144 CSM CD (nm) R (Correlation Coefficient) = SEM CD (nm) Good Correlation was obtained! By Dong gun Lee

$(Spectra Physics) 35 fs, 5 mj, 1 khz Shutter Ionization gas cell Diffraction 6 deg 3 2 1$

15 New CSM system with HHG Collaboration work with RIKEN and Osaka univ. High order harmonics (59 th nm) of Sub tera-watt femto-second laser( 800 nm) CSM EUV CCD Pinhole Zr/Si Filter Spitfire (Spectra Physics) 35 fs, 5 mj, 1 khz Shutter Ionization gas cell Diffraction 6 deg femto-second laser monochromator XY Stage with encoder HHG Coherent EUV source Vacuum Chamber

16 A new metrology system development from to Coherent Scattering System ( ) Commercial System Development University of Hyogo High hermonic generated High power source coherent source ( ) 2012) by Osaka Univ. ( )Riken 250 W(607 nm,10 fs,5 khz,50 mj Ti/sappire 35 fs,1 khz,5 mj 1 nw 50 μw(13.5 nm,50 fs,5 khz,0.5 nj Funded by JST CREST

17 Conclusion A coherent scattering EUV microscope has been developed. Up to now, the LS patterns of 100 nm hp and the hole pattern of 120 nm hp was reconstructed. CD values of 256 nm pitch L&S were measured. This value was good correlation with CD-SEM. We are developing a new CSM system with high order harmonic EUV light in collaboration with RIKEN and Osaka Univ..

The Coherent EUV Scatterometry Microscope for Actinic Mask Inspection and Metrology

The Coherent EUV Scatterometry Microscope for Actinic Mask Inspection and Metrology Tetsuo Harada* 1,3, Masato Nakasuji 1,3, Teruhiko Kimura 1,3, Yutaka Nagata 2,3, Takeo Watanabe 1,3, Hiroo Kinoshita