Development of EUV-Scatterometry for CD Characterization of Masks. Frank Scholze, Gerhard Ulm Physikalisch-Technische Bundesanstalt, Berlin, Germany

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1 Development of EUV-Scatterometry for CD Characterization of Masks PB Frank Scholze, Gerhard Ulm Physikalisch-Technische Bundesanstalt, Berlin, Germany Jan Perlich, Frank-Michael Kamm, Jenspeter Rau nfineon Technologies, München, Germany Christian Holfeld Advanced Mask Technology Center, Dresden, Germany 2nd nternational EUVL Symposium, 30 September - 2 October 2003

2 Outline PB Motivation EUV measurement facilities at PTB/BESSY, Berlin Scatterometry of topographical masks Comparison to simulation Conclusions 2nd nternational EUVL Symposium, 30 September - 2 October 2003

3 Co-Operation nfineon-ptb PB ssue: Complex image formation of EUV masks requires accurate measurement of topographical structure. Partners: nfineon Maskhouse Munich as a leading-edge maskshop for advanced photomasks. PTB as leading provider of EUV metrology capabilities. Goal: evaluate applicability of EUV-scatterometry. Future activities on EUV masks will be performed by the new Advanced Mask Technology Center (AMTC), Dresden. 2nd nternational EUVL Symposium, 30 September - 2 October 2003

4 PTB Radiometry Laboratory PB BESSY main parameters diameter of experimental hall: 120 m circumference of storage ring: 240 m 2nd nternational EUVL Symposium, 30 September - 2 October 2003

5 PTB Radiometry Laboratory PB 5 PTB Undulator 4c bending magnets electrons 3c 4b 4a 3a 2 3b 65 m 1 plane grating monochromator 4a undispersed undulator radiation 30 ev to 1800 ev 2 four crystal monochromator 1.75 kev to 10 kev 4b plane grating monochromator at undulator 20 ev to 1900 ev 3a undispersed bending magnet radiation 4c deflected undispersed undulator radiation 3b normal incidence monochromator radiation source calibration 3 ev to 35 ev 5 normal incidence monochromator detector calibration 3 ev to 35 ev 3c deflected undispersed bending magnet radiation 2nd nternational EUVL Symposium, 30 September - 2 October

6 EUV Activities PB Radiometry beamline: reflectometry rel. uncert. reflectance: u=0.14% detector calibration rel. uncert. responsivity: u=0.3% Focused bending magnet: optics lifetime-testing Direct undulator radiation: system metrology, first European EUV prints with MET 2nd nternational EUVL Symposium, 30 September - 2 October 2003

7 PB PTB Reflectometer Det- R 2Θ Det- X Det. Φ Θ z Φ y x tilt Axis θ Tilt φ x y z Det. X Det. R Det. φ 2θ θ Range -30 to to 10 0 to mm to 90 mm -10 mm to 300 mm -15 mm to 140 mm 0 mm to 120 mm 150 mm to 550 mm 0 to to 190 Accuracy: 10µm or 0.01 Diameter: 2 m Length: 2.1 m Weight: 3 t 2nd nternational EUVL Symposium, 30 September - 2 October 2003

8 PTB Reflectometer Sample Holder PB Mask 1 ML Mirror Transfer with robot 2nd nternational EUVL Symposium, 30 September - 2 October 2003

9 Motivation PB Complex image formation of EUV masks requires accurate measurement of topographical structure, e.g. sidewall angle. Optical scatterometry already used for fast characterization of mask topography, but limited to optical spectrum. Extension to shorter wavelengths desirable due to resolution. Actinic measurement needed to provide further information on mask performance, e.g. local EUV-reflectance in patterned region. 2nd nternational EUVL Symposium, 30 September - 2 October 2003

10 Scattering Theory PB Fraunhofer diffraction at a planar structure ( θ ) = ( ) 0 sin β sin N α 2 N β sinα 2 2 Form factor: information on CD q β = π CD x 2π Diffraction lines: information on pitch q x = 2π/pitch q x = 2π/CD q α = π pitch x 2π 2nd nternational EUVL Symposium, 30 September - 2 October 2003

11 Scatterometry of Lines & Spaces PB Scan of the direction of the outgoing photon beam at constant wavelength significant variation of q z 2nd nternational EUVL Symposium, 30 September - 2 October 2003

12 Theory - Scattering with Depth Profile PB Diffracted orders ncident beam at 5 CDeff Effective reflection depth 3D mask structure of EUV masks : Shadowing effects due to oblique angle of incidence effective CD Reflection at distributed Bragg-reflector effective plane of reflection Effective geometrical model : reduced CD at large scattering angles due to shadowing. 2nd nternational EUVL Symposium, 30 September - 2 October 2003

13 Comparison to Rigorous Modelling PB γ var Cr CD var SiO 2 CD: 412 nm, 35 absorber angle Rigorous modeling of topographical mask: ❶ Calculate intensity of diffraction orders with rigorous coupled wave analyis. ❶ Best-fit to experimental data. Extraction of bottom-cd, and absorber- sidewall angle. 2nd nternational EUVL Symposium, 30 September - 2 October 2003

14 Conclusions PB ❶ High-accuray reflectometry used to measure EUV-scattering. ❶ EUV-scatteromtery provides topographical information of multilayer masks. ❶ High-accuray EUV-scatterometry provides a tool for testing EUV mask modelling. ❶ Further development aims for optimized measurement procedures, improved modelling and fast automated fitting. 2nd nternational EUVL Symposium, 30 September - 2 October 2003