Low Order Aberrations Correction of Extreme UltravioletLow‐Order Aberrations Correction of Extreme Ultraviolet Imaging Objective with Deformable Multilayer MirrorImaging Objective with Deformable Multilayer Mirrorg g j y

Mi i TOYODA R SUNAYAMA d Mihi YANAGIHARAMitsunori TOYODA, Ryo SUNAYAMA, and Mihiro YANAGIHARA,Mitsunori TOYODA, Ryo SUNAYAMA, and Mihiro YANAGIHARA,I i f M l idi i li R h f Ad d M i l T h k U iInstitute of Multidisciplinary Research for Advanced Materials, Tohoku Univ.Institute of Multidisciplinary Research for Advanced Materials, Tohoku Univ.

Introduction D f bl Mi FEM calculationsIntroduction Deformable Mirror FEM calculationsIntroduction Deformable MirrorLoad force: 10 NLoad force: 10 N

Annular Zernike coefficients (rms )Pi t ( ) 7 82

Annular Zernike coefficients (rms.)Piston z1 (m) 7.82Tilt ( ) 1 52

Hi h ifi ti ( 1500) CCD id b tiTilt x z2 (m) -1.52Tilt ( ) 3 91 High magnification (x1500) : CCD video observation Tilt y z3 (m) 3.91

P ( ) 0 09 Small off‐axis aberrations: Wide FOV (φ=200μm) Power z4 (nm) 0.09Small off axis aberrations: Wide FOV (φ 200μm) Astigmatism x z5 (nm) -3.96Astigmatism y z6 (nm) -0.69

E i t l R ltExperimental ResultsExperimental Resultsé f ff

pMaréchal criterion for diffraction‐limited imaging g g

1010μm

M h i l d iMechanical designgWavefront measurement with sub‐nm accuracy

EUV microscope with multilayer mirror opticsy

EUV microscope with multilayer mirror optics

φ=50 mm

Concave mirror (M1) is glued to three holding arms Concave mirror (M1) is glued to three holding arms. Flexure springs (arrow) absorb thermal expansion.e u e sp gs (a o ) abso b e a e pa s o Picomotors (A1 A3) can apply force (max: 20 N) on Picomotors (A1‐A3) can apply force (max: 20 N) on

holding plate (H1) to correct astigmatism. g p ( ) g Three axis stage with Picomotors (A4 A6) for fine Three‐axis stage with Picomotors (A4‐A6) for finealignment of convex mirror (M2).g ( )

Reflection image of EUV lithography maskReflection image of EUV lithography mask

10μm

Two torsional moments (twists) in opposite direction Two torsional moments (twists) in opposite directionapplied to holding arms (red arrows) modifypp g ( ) yradius of curvature of mirror surfaceradius of curvature of mirror surface. 

Torsional moments are generated with force appliedg ppto holding plate (yellow arrow)to holding plate (yellow arrow). 

REFERENCES[1] M Toyoda Japan Patent No P5489034 Mar 7 2014[1] M. Toyoda, Japan Patent, No. P5489034, Mar. 7, 2014.[2] M. Toyoda, "Flat-field anastigmatic mirror objective for high-magnification extreme ultraviolet microscopy",[ ] y , g j g g py ,

Adv. Opt. Techn., vol. 4, no. 4, pp. 339-346, 2015.d l l h l i l li h h k b i i hi h[3] M. Toyoda et al., "At-wavelength extreme ultraviolet lithography mask observation using a high-

magnification objective with three multilayer mirrors" Appl Phys Express vol 5 p 112501 2012magnification objective with three multilayer mirrors , Appl. Phys. Express, vol. 5, p. 112501, 2012.[4] M. Toyoda et al., " Demonstrating 30-nm spatial resolution of three-multilayer-mirror objective for extreme[ ] y , g p y j

ultraviolet microscopy: Imaging test by observing lithography mask", Appl. Phys. Express, vol. 7, p. 102502,20142014.

[5] M Born and E Wolf "Principles of Optics" Oxford UK: Pergamon Press 1980[5] M. Born and E. Wolf, Principles of Optics , Oxford, UK: Pergamon Press, 1980.[6] V. N. Mahajan, "Zernike annular polynomials for imaging systems with annular pupils" J. Opt. Soc. Am.

vol. 71, pp. 1408-1408, 1981.