Kenneth Goldberg, SPIE 2005, 5900–16 Ultra-high-accuracy optical testing: creating diffraction-limited short- wavelength optical systems Kenneth A. Goldberg

Kenneth Goldberg, SPIE 2005, 5900–16 Ultra-high-accuracy optical testing: creating diffraction-limited short- wavelength optical systems SPIE 2005, Kenneth A. Goldberg Patrick Naulleau, Senajith Rekawa, Paul Denham, J. Alexander Liddle, Keith Jackson, Erik Anderson, K. Bradley, R. Delano, B. Gunion, B. Harteneck, B. Hoef, G. Jones, C. D. Kemp, D. Olynick, R. Oort, F. Salmassi, R. Tackaberry Center for X-Ray Optics, Lawrence Berkeley National Laboratory in collaboration with J. Taylor, G. Sommargren, H. Chapman, D. Phillion,K. Dean, et al. M. Johnson, A. Barty, R. Soufli, S. Bajt,et al. International Lawrence Livermore National Laboratory Sematech and the EUV LLC and VNL

Kenneth Goldberg, SPIE 2005, 5900–16 Please see Soufli, et al. SPIE (Mon) SDO / AIA material courtesy of LMSAL CHANDRA X-Ray Observatory Nested glancing-incidence mirrors Angular Resolution: ~0.5” in 0.5–10 keV NASA / CXC / SAO AIA Normal-incidence mirrors Angular Resolution: 0.6” per pixel Consider two state-of-the-art telescopes SDO — Solar Dynamics Observatory

Kenneth Goldberg, SPIE 2005, 5900–16 Resolution is set by design compromises Telescope size Detector-pixel size Fabrication limits Collection efficiency etc. However, thanks to the semiconductor industry, technology for much higher quality lenses is now available in the EUV. So, what does the semiconductor industry want with EUV lenses? Better optics / Better angular resolution is possible

Kenneth Goldberg, SPIE 2005, 5900–16 Lithography follows Moore’s Law By 2009–13, mass production of lithographic-quality EUV lenses. 45 nm 32 nm 22 nm 15 nm GB 34 GB 69 GB EUV DRAM half-pitch Intel plans industry plansDRAM ––––––––

Kenneth Goldberg, SPIE 2005, 5900–16 EUV projection lenses may be the highest quality optical systems ever produced = 13 nm, ~90 eV Mo/Si multilayer-coated for near-normal incidence: R ≈ 70% (Lawrence Livermore, Lawrence Berkeley, et al.) Diffraction-limited spatial resolution Up to 0.3 NA, ƒ/1.67 Rayleigh resolution: 1.22 / NA  27-nm half-pitch Diffraction-limited EUV optics for photolithography MET projection lens Courtesy J. Taylor, LLNL

Kenneth Goldberg, SPIE 2005, 5900–16 patterned reflective mask resist-coated wafer Engineering Test Stand Sandia National Labs. Courtesy, Bill Replogle Industry-funded EUV projection lithography research at Berkeley, Livermore, Sandia Nat’l Labs

Kenneth Goldberg, SPIE 2005, 5900–16 Reaching “diffraction-limited” performance Rayleigh criterion /4 P-V 3.35 nm Maréchal criterion /14 rms 0.96 nm Lithographic criterion ~ /50 rms 0.27 nm Ultra-high-accuracy optical testing is the key  Visible-light and EUV interferometry with sub-Å RMS accuracy. If you can measure it, you can make it.

Kenneth Goldberg, SPIE 2005, 5900–16 Hubble Space Telescope Before Hubble repair, 1993 COSTAR optic installed After Inaccurate interferometry cost NASA $Billions Kenneth Goldberg, SPIE 2005, 5900–16

Comparison of slope and roughness requirements Goal32-nm half-pitch Slope error0.3–1.0 µrad 37-Zernikesmeasured MSFR≤ 1–2 Å mid spatial-freq. HSFR ≤ 1–2 Å high spatial-freq. EUV Lithographic Optics SDO — AIA instrument Goal0.5 arcsec Slope error≤ 5 µrad full aperture Roughness≤ 4.4 Å 1/ƒ = (4 µm, 4 mm) Micro-roughness≤ 4.4 Å 1/ƒ = (9 nm, 4 µm) The specs are several times tighter, and achievable

Kenneth Goldberg, SPIE 2005, 5900–16 Numerous factors contribute to the wavefront

Kenneth Goldberg, SPIE 2005, 5900–16 Pushing visible-light interferometry Livermore scientists developed the PSDI or Sommargren Interferometer Single Mirror Two beams are launched into a fiber with a time delay. A pinhole in a mirror creates the test and reference beams. Complete System One fiber + pinhole at each conjugate. G. Sommargren, J. Taylor, M. Johnson, D. Phillion, H. Chapman, A. Barty, et al. (LLNL) (SPIE 5869–28,30)

Kenneth Goldberg, SPIE 2005, 5900–16 High sensitivity to multilayer properties

Kenneth Goldberg, SPIE 2005, 5900–16 EUV interferometers used at the ALS

Kenneth Goldberg, SPIE 2005, 5900–16 EUV interferometers used at the ALS — PS/PDI

Kenneth Goldberg, SPIE 2005, 5900–16 EUV interferometers used at the ALS — LSI

Kenneth Goldberg, SPIE 2005, 5900–16 the illuminated MET pupil transmitted light EUV Light Kenneth Goldberg, SPIE 2005, 5900–16

PS/PDI interferogram ultra-high accuracy EUV Light Kenneth Goldberg, SPIE 2005, 5900–16

shearing interferogram efficient measurement method EUV Light Kenneth Goldberg, SPIE 2005, 5900–16

2-mirror, 10x Schwarzschild objectives NA ≥ 0.08 ƒ / 6.3 Berkeley 10x10xI10xA10xB 10xA10xB2 F2X ETS Set-1ETS Set-2MET 4-mirror, 4x ETS projection optics NA = 0.1 ƒ / mirror, 5x MET optic NA = 0.3 ƒ / 1.67 A long track record of EUV Interferometry, alignment optimization and imaging at LBNL (since ’93) higher resolution higher qualitytime

Kenneth Goldberg, SPIE 2005, 5900–16 ETS Projection Optic: off-axis, large field M1 M4 M3 M2 ~1.1-m mask-to-wafer Work sponsored by the EUV LLC

Kenneth Goldberg, SPIE 2005, 5900–16

The 0.3-NA Micro-Exposure Tool: high resolution Courtesy of J. Taylor, LLNL MET NA = 0.3, ƒ/ 1.67 = 13.4 nm 5x demag. 200 x 600 µm field capable of ≥ 12-nm printing Work sponsored by International SEMATECH Illumination Coating & Assembly: LLNL Mirrors: Zeiss

Kenneth Goldberg, SPIE 2005, 5900–16 MET at-wavelength interferometry and alignment EUV interferometry maps the 3-D field of view. Alignment sets astigmatism, coma, spherical aberration arbitrarily small. MET Micro-Exposure Tool Wavefront measurement during alignment astig coma sph ab trifoil h-o s nm 0.06 nm 0.04 nm 0.14 nm 0.37 nm RMS0.55 nm  /24.5 central field point

Kenneth Goldberg, SPIE 2005, 5900–16 one nm /24.5 = 0.55 nm /50 = 0.27 nm EUVL  -tool, required wavefront quality /135 = ~100 pm EUV interferometer 0.3 NA /330 = 40 pm EUV interferometer 0.1 NA /255 = 53 pm Bohr radius, a 0 Small tolerances necessitate ultra-high accuracy wavefront quality of best EUV optic to date

Kenneth Goldberg, SPIE 2005, 5900–16 The keys to achieving ultra-high accuracy 1)Innovative calibration methods (null tests) 2)New interferogram analysis techniques for minimizing phase-measurement errors 3)High-quality “reference” pinholes (Nanowriter) We isolate and measure geometric & systematic error sources so they can be subtracted.

Kenneth Goldberg, SPIE 2005, 5900–16 two-pinhole null-test interferogram system calibration for high accuracy Kenneth Goldberg, SPIE 2005, 5900–16

grating null-test interferogram system calibration for high accuracy Kenneth Goldberg, SPIE 2005, 5900–16

Pinhole-array diffraction object pinhole image pinhole 100 nm 25 nm TEM SEM object pinholes image pinholes Nanofabrication (Nanowriter) TEMPEST-3D Modeling vector E-M field simulations 150-nm Ni 100-nm Ni Intensity diffraction angle Developing state-of-the art pinholes for spherical reference-wave accuracy

Kenneth Goldberg, SPIE 2005, 5900–16 Coded as 80 nm (1:1) narrowed by exposure bias (x1.4) 39-nm isolated lines 0.1-NA ETS optic: lithography at LBNL 13.5 nm wavelength  = 0.7, partial coherence DOF = ± 0.5 µm EUV-2D resist, 120-nm thick The absence of astigmatism confirms accuracy

Kenneth Goldberg, SPIE 2005, 5900–  m 45 nm 30 nm 35 nm 25 nm 1.8  m 0.3-NA MET: Modulation down to ~25 nm Rohm and Haas photo-resist R. Brainard, et al.

Kenneth Goldberg, SPIE 2005, 5900–16

Direct visible / EUV comparisons lead to improved accuracy

Kenneth Goldberg, SPIE 2005, 5900–16 We also cross-calibrate the different EUV techniques Inter-comparisons have also improved EUV testing methods. visible-lightEUV PS/PDIEUV shearing

Kenneth Goldberg, SPIE 2005, 5900–16 Conclusions High-quality EUV optics are available now largely due to the development of EUV lithography slope errors:< 1 µrad roughness:≤ 1–2 Å micro-roughness:≤ 1–2 Å Ultra-high accuracy interferometry is required for fabrication and alignment: visible (LLNL) and EUV (LBNL). We have extended our EUV measurement techniques to 0.3 NA, ƒ/1.67 – Achieved Wavefront quality of 0.55 nm ( /24.5). – Demonstrated interferometer accuracy of 1 Å, and below.

Kenneth Goldberg, SPIE 2005, 5900–16 Extra slides follow...

Kenneth Goldberg, SPIE 2005, 5900–16 Interferometry across the field of view [nm] Note: diameter ~ magnitude image-plane field measurement Initial measurements showed a large spherical aberration 0.8–0.9 nm Field measurements are made at 9(x,y)  3(z) = 27 points, 135 interferograms, ~ 3 hours.

Kenneth Goldberg, SPIE 2005, 5900–16 Using interferometry to optimize the MET alignment [nm] Note: diameter ~ magnitude image-plane field measurement Reduced the aberration magnitude to 0.55 nm = /24.5 Set astig., coma, and sph. ab. to ~ /225 – /340

Kenneth Goldberg, SPIE 2005, 5900–16 Different kinds of interferometry are used Visible-light Sommargren Interferometer (LLNL) EUV Knife-edge (Foucault) testing Lateral Shearing Interferometry (LSI) - cross-grating technique Phase-shifting point-diffraction interferometry - ultra-high accuracy - invented at CXRO Hartmann test - best for low-NA

Kenneth Goldberg, SPIE 2005, 5900–16 astigmatism111 pm coma47 pm spherical297 pm trifoil292 pm  37 RMS703 pm EUV deviation from a perfect, spherical wavefront = 13.4 nm