Overview of ALD-Activities for Optical Applications: Materials, Refractive and Diffractive Optics

Transcription

1 Overview of ALD-Activities for Optical Applications: Materials, Refractive and Diffractive Optics Adriana Szeghalmi, 1,2, S. Shestaeva 1, Astrid Bingel 1 L. Ghazaryan 2, K. Pfeiffer 2, S. Ratzsch 2 1 Fraunhofer Institute for Applied Optics and Precision Engineering 2 Friedrich Schiller University Jena, Institute of Applied Physics a.szeghalmi@uni-jena.de Workshop Optical Coatings for Laser Applications Buchs Page 1

2 Outline Introduction Coating equipment Results Materials Interference Coatings Diffractive Optics Outlook Page 2

3 Dr. Adriana Szeghalmi Professional career since final degree 10/2015 to date Group Manager ALD for Optics Fh G-IOF Jena 05/2010 to date Emmy Noether Group Leader FSU Jena 05/ /2010 Postdoc, Max Planck Institute of Microstructure Physics (Prof. U. Gösele, Dr. M. Kn e z) Halle (Saale) 04/ /2007 Postdoc, University of Manitoba, Canada (Prof. K. M. Gough) Winnipeg University education 07/ /2005 PhD studies, University of Würzburg (Prof. W. Kiefer) 04/ /2001 Exchange student at the University of Würzburg 10/ /2001 Study of Chemistry and Physics, Babes-Bo lya i University, Romania Page 3

4 ALD Team Lilit Ghazaryan Kristin Pfeiffer Vivek Beladiya Svetlana Shestaeva Astrid Bingel David Kästner Alumni: M. Sc. Haiyue Yang Dr. Pascal Genevée M. Sc. Er n est Ahiavi Dr. St ephan Rat zsch Page 4

5 The ALD Solution to Enhance Optical Performance ESA, Sentinel-2 [1] Ti O 2 1 µm [1] [2] L. Ghazaryan, A. Szeghalmi, E. B. Kley, U. Schulz, DPMA Anmeldung Page 5

6 Why ALD? Ir conformality [1] Al 2 O 3 - Thickness (nm) ALD cycles uniformity precise thickness control ALD [1] T. Weber, T. Käsebier, A. Szeghalmi, M. Kn e z, E. B. Kley, A. Tünnermann. Nanoscale Research Lett. 6 (2011) 558 [2] A. Szeghalmi et al., Applied Physics Letters, 2009, 94, /3. repeatability low roughness Ta 2 O 5 / Al 2 O 3 Nanolaminate (2.3 nm / 6.7 nm) x N [2] Page 6

7 ALD at omic layer-by-layer coating technology Si O 2 ALD cycle HSi(N(CH 3 ) 2 ) 3 O 2 Plasma Page 7

8 ALD at omic layer-by-layer coating technology Si O 2 ALD cycle HSi(N(CH 3 ) 2 ) 3 O 2 Plasma Page 8

9 ALD at omic layer-by-layer coating technology Si O 2 ALD cycle HSi(N(CH 3 ) 2 ) 3 O 2 Plasma Page 9

10 ALD at omic layer-by-layer coating technology Si O 2 ALD cycle HSi(N(CH 3 ) 2 ) 3 O 2 Plasma Ar purge Page 10

11 ALD at omic layer-by-layer coating technology Si O 2 ALD cycle HSi(N(CH 3 ) 2 ) 3 O 2 Plasma Ar purge Page 11

12 ALD at omic layer-by-layer coating technology Si O 2 ALD cycle HSi(N(CH 3 ) 2 ) 3 O 2 Plasma Ar purge Ar purge Page 12

13 ALD at omic layer-by-layer coating technology Si O 2 ALD cycle HSi(N(CH 3 ) 2 ) 3 O 2 Plasma Ar purge Ar purge Page 13

14 Coating Equipment 1. OpAL PEA LD tool Oxford Plasma Technologies (UK) Open loaded ALD tool To p -Flow reactor ICP p la sm a Up to 200 mm diameter wafers (150 mm square) Height up to 20 mm Up to 4 precursors (H 2 O + 3 Metal Precursors) Temperature range 25 C 200 C Ellipsometry ports, Woollam ellipsometer ca. 400k Installed 2011 Oxides Page 14

15 Coating Equipment 2. Sunale R200 PEALD tool Picosun Oy (F) Load-lock and open loaded ALD Hot-wall top-flow dual chamber design RF Pla sm a Up to 200 mm diameter wafers (150 mm square) Height up to 100 mm Up to 6 precursors (H 2 O + 5 Metal Precursors) Temperature range 25 C 500 C Load-lock integrated in GloveBox ca. 400k Installed 2013 Metals and Oxides Page 15

16 Larger Reactor Configuration In commissioning Diameter 330 mm Height up to 100 mm Thermal and Plasma Enhanced ALD To be installed March IOF Jena Page 16

17 Outline Introduction Coating equipment Results Materials Interference Coatings Diffractive Optics Outlook Page 17

18 Materials development of the thermal and/ or PEALD processes SiO 2, Al 2 O 3, TiO 2, HfO 2, Ta 2 O 5 MgF 2, Ca F 2, La F 3 iridium alucones & nanoporous Al 2 O 3 composite materials & nanoporous SiO 2 literature: Ru, Ag, Au, W, graphene, nitrides, SrTiO 3, Nb 2 O 5, ZrO 2 optical properties morphology mechanical properties h cc = ΓEE ff ZZσσ 2 h critical coating thickness E f Elastic modulus film Γ fracture resistance Z geometrical factor (1.976) σ mechanical stress Page 18

19 Oxides: Summary of Ref ract ive Index Refractive index 3,0 2,8 2,6 2,4 2,2 2,0 1,8 1,6 HfO2 100 C SiO2 100 C Al2O3 200 C TiO2 100 C Al2O3:TiO2 120 C 1, Wavelength (nm) Page 19

20 TiO 2 Titanium(IV) isopropoxide Ti[OCH(CH 3 ) 2 ] 4 heated and bubbled at C + H 2 O H 2 O 2 O 2 Plasma Titanium(IV) chloride TiCl 4 + H 2 O Page 20

21 TiO 2 Film Growth Linear ALD growth with number of cycles Influence of Deposition Temperature and O 2 -Plasma Page 21

22 TiO 2 Refractive Index PEALD processes provide higher refractive index at lower temperature than the thermal ALD of titania Temperature has little influence in PEALD of titania n = ~0.03 n = ~ 0.4 Page 22

23 TiO 2 Thickness Uniformity TiO 2 /Al 2 O 3 PEALD 120 C Ø 150 mm Si wafer: SD 1 σ = 1.07% Homogeneity (Max-Min/2d average ) = 2.1% nm = ± Page 23

24 TiO 2 Tensile Mechanical St ress σ decreases in nanolaminates Page 24

25 HfO 2 Tetrakis(dimethylamino)hafnium(IV) [(CH 3 ) 2 N] 4 Hf heated and bubbled at 50 C + O 2 Plasma Page 25

26 Optical Properties Influence of Temperature high scattering losses above 200 C deposition temperature Page 26

27 Thickness and Refractive Index Uniformity Position Y (mm) HfO 2 PEALD 100 C Ø 200 mm Si wafer: SD 1 σ = 2.24% Homogeneity (Max-Min/2d average ) = 4.5% Plasma flow from the top Thickness (nm) 49,00 49,50 50,00 50,50 51,00 51,50 52,00 52,50 53,00 53,50 54,00 Position Y (mm) n = ± Refractive index 1,886 1,889 1,892 1,895 1,898 1,901 1,904 1,907 1, Position X (mm) Position X (mm) Page 27

28 HfO 2 Refractive Index PVD & ALD 400nm 2,2 2,1 2,0 Xe Ar 100 C 300 C 200 C 1,9 1,8 1,7 EBE IAD PIAD MS IBS PLD IP ALD O. Stenzel, S. Wilbrandt, S. Yulin, N. Kaiser, M. Held, A. Tünnermann, J. Biskupek, U. Kaiser, Opt. Mater. Express 2011, 1, 278. Page 28

29 HfO 2 TEM image deposited at 100 C ca. 5 nm Nanocrystallites ca. 3.5 nm HfO 2 /SiO 2 composite layer at the Si-wafer interface Page 29

30 HfO 2 Tensile Mechanical St ress σ increases with increasing deposition temperature due to crystallization σ slightly increases with increasing ion energy 900 Stress (MPa) Bulusu HfO2 -FSU SP LEP HEP Temperature ( C) Page 30

31 HfO 2 Tensile Mechanical St ress σ decreases in nanolaminates (HfO 2 /SiO 2 and HfO 2 /Al 2 O 3 ) 2, ,025 Refractive index Film stress 650 Refractive index 2,000 1,975 1, Film stress (MPa) 1, ,900 Standard HfO 2 homogeneous without needles NL 15/1.5 NL 15/3 NL 7/3 400 Page 31

32 Al 2 O 3 Trimethylaluminum (CH 3 ) 3 Al own vapour pressure + H 2 O O 2 Plasma Aluminum chloride + H 2 O AlCl 3 Page 32

33 100 nm Al 2 O 3 on 200 mm Si w afer Page 33

34 Influence of Deposition Temperature impact on reproducibility of refractive index temperature has less influence in PEALD processes than in thermal ALD Refractive index n 1,75 Al 2 O 3 Plasma ALD 25 C Al 2 O 3 Plasma ALD 120 C Al 2 O 3 Plasma ALD 200 C 1,70 1,65 1,60 1,55 Al 2 O 3 Plasma ALD 250 C Al 2 O 3 Plasma ALD 300 C Refractive index 1,85 1,80 1,75 1,70 1,65 Al2O3-200 C thermal Al2O3-120 C thermal Wavelength (nm) n = within measurement accuracy 1, n = Wavelength (nm) Page 34

35 Thickness Uniformity Al 2 O 3 thermal 300 C Ø 200 mm Si wafer: SD 1 σ = 1.1% Homogeneity (Max-Min/2d average ) = 2.44% n = ± Position Y [mm] Position X [mm] Thickness (nm) Position Y [mm] Position X [mm] Refractive index Page 35

36 Opt ical Losses Al 2 O 3 with low optical losses have been achieved confirmed by laser calorimetry measurements Thermal 1064 nm on 300 nm thick Al 2 O 3, ca. 2,5 ppm Page 36

37 Al 2 O 3 Tensile Mechanical St ress σ decreases with increasing deposition temperature PEALD coatings show lower mechanical stress than thermal ALD alumina residual stress = (thermal stress + intrinsic stress) Stress [MPa] 600 Krautheim Tripp Miller 500 Bulusu Ylivaara FSU-Thermal 400 FSU-PEALD Temperature [ C] Page 37

38 Al 2 O 3 FTIR Spect ra -OH content decreases with increasing temperature different hydrogen-bonding in thermal vs. PEALD processes Absorbance (a.u.) 0,006 0,004 0, Plasma 120 C Plasma 200 C Plasma 250 C Plasma 300 C Absorbance (a.u.) 0,006 0,004 0, Plasma 120 C Thermal 120 C 0,000 0, Wavenumber (cm -1 ) Wavenumber (cm -1 ) Page 38

39 SiO 2 Tris(dimethylamino)silane [(CH 3 ) 2 N] 3 SiH own vapour pressure + O 2 Plasma Bis(diethylamino)silane [(C 2 H 5 ) 2 N] 2 SiH 2 heated and bubbled at 70 C Page 39

40 Influence of Substrate Material calibration curves are required Page 40

41 Opt ical Losses materials with low optical losses have been achieved confirmed by laser calorimetry measurements SiO 2 PEALD 200 C example 1,0 SiO2 Plasma Substrate Optical losses (%) 0,5 0,0-0, Wavelength 1064 nm on 300 nm thick SiO 2, ca. 1,5 ppm (Laser Zentrum Hannover) Page 41

42 Thickness Uniformity SiO 2 PEALD 100 C Ø 200 mm Si wafer: SD 1 σ = 1.36% Homogeneity (Max-Min/2d average ) = 2.31% n = ± Position Y (mm) Thickness (nm) 100,1 100,3 100,5 101,0 101,5 102,0 102,5 103,0 103,5 104,0 104,6 105,0 Position Y (mm) Refractive index 1,4460 1,4463 1,4465 1,4468 1,4470 1,4473 1,4475 1,4477 1, Position X (mm) Position X (mm) Page 42

43 Composites and Nanoporous SiO 2 atomically mixed Al 2 O 3 /SiO 2 composites and selective removal of Al 2 O 3 N Y X n@632.8 nm Al 2 O 3 : Si O 2 Si Al O L. Ghazaryan, A. Szeghalmi, E. B. Kley, U. Schulz, DPMA Anmeldung L. Ghazaryan, A. Szeghalmi, E. B. Kley, DPMA Anmeldung. Anmeldetag 24. Februar Page 43

44 Nanoporous SiO 2 atomically mixed Al 2 O 3 /SiO 2 composites and selective removal of Al 2 O 3 precisely control porosity and refractive index through atomic composition Before etching 2:2 3:2 4:2 Page 44

45 Applications of Nanoporous SiO 2 antireflection coatings one layer double side coating 92 nm each side n = 1.22 Over 98 % Transmittance in VIS Low optical losses Page 45

46 Applications of Nanoporous SiO 2 diffusion membrane High efficiency transmission gratings ALD Al 2 O μm Planarisation Al 2 O 3 :SiO 2 alloy 1 µm Page 46

47 Outline Introduction Coating equipment Results Materials Interference Coatings Diffractive Optics Outlook Page 47

48 Antireflection Coating SEM Image Total 391 nm SiO HfO SiO HfO SiO HfO SiO HfO N-SF8 su b st rat e Page 48

49 Antireflection Coatings [3] K. Pfeiffer, S. Shestaeva, A. Bingel, P. Munzert, L. Ghazaryan, C. van Helvoirt, W. M. M. Kessels, U. Sanli, C. Grévent, G. Schütz, M. Putkonen, I. Buchanan, L. Jensen, D. Ristau, A. Tünnermann, A. Szeghalmi. Opt. Mater. Express 6 (2016) 660 [4] A. Szeghalmi, M. Helgert, R. Brunner, F. Heyroth, U. Gösele, M. Kn e z. Appl. Opt. 48 (2009) 1727 Page 49

50 Dichroic Mirror at 355 nm 30 layers [HfO 2 (Al 2 O 3 ) and SiO 2 ] ca. 1.9 µm total thickness high adhesion coating to substrate >99.5% reflectance at 45 Reflectance (%) Exp. Design Total deposition time: ~4 days NO optical monitoring av.-pol. av.-pol. AOI=45 Reflectance (%) Reflectance (%) Exp. Design av.-pol. av.-pol Wavelength (nm) Exp. Design AOI=45 av.-pol. av.-pol. AOI= Wavelength (nm) Wavelength (nm) Page 50

51 Highly Reflective Dichroic Mirror cracking of the coating and substrate Page 51

52 Highly Reflective Dichroic Mirror cracking of the coating and substrate crack occurs after deposition Hf O 2 Hf O 2 Si O 2 Page 52

53 Outline Introduction Coating equipment Results Materials Interference Coatings Diffractive Optics Outlook Page 53

54 Resonant Waveguides nanostructure + ALD coating 481 nm C-Paste PC Film Thickness ~ 120 nm (~2 hours deposition) Narrow Band A. Szeghalmi, E. B. Kley, M. Kn e z. J. Phys. Chem. C 114 (2010) A. Szeghalmi, M. Helgert, R. Brunner, F. Heyroth, U. Gösele, M. Kn e z. Adv. Funct. Mater. 20 (2010) 2053 Page 54

55 Polarizers Resist grating sputtering Ir wire grid polarizer ALD coating 100 nm IBE etching Ir ALD coating ICP etching resist [1] T. Weber, T. Käsebier, A. Szeghalmi, M. Kn e z, E. B. Kley, A. Tünnermann. Nanoscale Research Lett. 2011, 6, 558 [2] Y. Bourgin, T. Siefke, T. Käsebier, P. Genevée, A. Szeghalmi, E. B. Kley, U. D. Zeitner. Optics Express, 2015, 23, Page 55

56 High Efficiency Transmission Gratings measured diffraction efficiency (-1 order) grating for TE-Polarisation 97.5% measured diffraction efficiency (-1 order) grating for TM-Polarisation 95% Al 2 O 3 /TiO nm Diffraction Efficiency (% ) SiO nm Wavelength (nm) S. Ratzsch, E. B. Kley, A. Tünnermann, A. Szeghalmi. Materials, 2015, 8, S. Ratzsch, E. B. Kley, A. Tünnermann, A. Szeghalmi. Optics Express, 2015, 23, S. Ratzsch, E. B. Kley, A. Tünnermann, A. Szeghalmi. Nanotechnology, 2015, 26, (1-11). Page 56

57 High Index Contrast Grating fabricate a low fill-factor grating in SiO 2 conformal overcoating w ith ALD TiO 2 thickness ca. 44 nm FIB cross section TiO 2 50nm p=555nm 250nm 100 SiO 2 Efficiency [%] theory measurement Δλ = 130nm 85 0,76 0,78 0,80 0,82 0,84 0,86 0,88 0,90 Wavelength [µm] Page 57

58 ALD Jena (Fraunhofer IOF & Universit y) ALD Material Development Interference Coating Systems Nano and Microstructured Optics Adriana.Szeghalmi@iof.fraunhofer.de Page 58

59 Acknowledgement Andreas Tünnermann Ernst Bernhard Kley Uwe Zeitner Peter Munzert Ulrike Schulz Norbert Kaiser IAP and IOF colleagues Page 59