Unravelling the systematics in ion beam sputter deposition of SiO 2. M. Mateev, T. Lautenschläger, D. Spemann, C. Bundesmann

Transkript

1 Unravelling the systematics in ion beam sputter deposition of SiO 2 M. Mateev, T. Lautenschläger, D. Spemann, C. Bundesmann

2 Introduction 2 Outline Introduction Motivation Setup and growth parameters Characterization techniques Experimental results Summary and outlook

3 Introduction 3 Motivation Refractive index changes upon assisting ion bombardment Questions: Why? Talk Mühlleiten 2008 Systematics? Dual mode Assist source Target C. Bundesmann et al., Thin Solid Films 516 (2008) Sputter source Substrate

4 Introduction 4 Motivation Ion beam and geometrical parameters Energy and angular distribution of sputtered and scattered particles Film properties Extend systematic investigations to SiO 2 SiO 2 has many applications: multilayer coatings, semiconductor devices, Similarities and differences to ion beam sputter deposition of TiO 2 (Ag, Ge) Ag Ge TiO 2 R. Feder et al., Nucl. Instrum. Methods Phys. Res., Sect. B, 316 (2013) 198. R. Feder et al., Nucl. Instrum. Methods Phys. Res., Sect. B, 317A (2013) 137. C. Bundesmann et al., Thin Solid Films 551 (2014) 46. C. Bundesmann et al., Contrib. Plasma Phys. 55 (2015) 737. R. Feder et al., Nucl. Instrum. Methods Phys. Res., Sect. B, 334 (2014) 88. C. Bundesmann et al., Thin Solid Films 589 (2015) 487. T. Lautenschläger et al., Nucl. Instrum. Methods Phys. Res., Sect. B, 385 (2016) 30. C. Bundesmann et al., Nucl. Instrum. Methods Phys. Res., Sect. B, 395 (2017) 17. C. Bundesmann et al., Appl. Surf. Sci., in press.

5 Introduction 5 Setup and growth parameters Rotary table Ion source Target Ion energy: 0.5 / 1.0 / 1.5 kev Linear tables Ion species: Ar, Xe Incidence angle: 0, 30, 60 Substrate Emission angle: holder Rotary table R. Woyciechowski

6 Introduction 6 Characterization techniques Done Spectroscopic ellipsometry (SE) RBS AFM Film thickness, growth rate optical properties Composition Surface roughness In progress XRD XRR Crystallinity Mass density

7 Film properties 7 Film thickness (SE) Ion incidence angle varied Ion energy varied Aim: Maximum film thickness ~ 100 nm Maximum at polar emission angle between 40 and 60

8 Film properties 8 Growth rate (SE) Ion incidence angle varied Ion energy varied Increases with increasing ion energy or ion incidence angle, higher for sputtering with Xe than for sputtering with Ar (Total sputter yield) Over-cosine angular distribution, tilted in forward direction (anisotropy effects)

9 Film properties 9 Surface roughness (AFM) Ion incidence angle varied Ion energy varied Films are very smooth RMS roughness (σ) increases with increasing scattering angle Small differences between sputtering with Ar or Xe Mainly influenced by scattering geometry Related to energy of secondary particles, affects surface mobility

10 Film properties 10 Composition (RBS) Ion incidence angle varied Ion energy varied Films are stoichiometric (Si:O ~ 1:2) Incorporation of primary particles (correlated with scattering angle) Similar for Ar and Xe

11 x Xe [at. %] x Ar [at. %] Film properties 11 Composition (RBS) Ar_1 (60, 1000 ev) Ar_3 (30, 1000 ev) Ar_5 (0, 1000 ev) TiO 2 SiO 2 Ar_2 (30, 1500 ev) Ar_3 (30, 1000 ev) Ar_4 (30, 500 ev) Xe_1 (60, 1000 ev) Xe_3 (30, 1000 ev) Xe_5 (0, 1000 ev) Xe_2 (30, 1500 ev) Xe_3 (30, 1000 ev) Xe_4 (30, 500 ev) [ ] [ ] Higher amount of inert gas particles in TiO 2 films than in SiO 2 films, especially for Ar C. Bundesmann, et al., Appl. Surf. Sci., in presss, DOI: /j.apsusc

12 x Xe [at. %] x Ar [at. %] Film properties 12 Composition (RBS) Ar_1 (60, 1000 ev) Ar_3 (30, 1000 ev) Ar_5 (0, 1000 ev) TiO 2 SiO 2 M Ar M Ti = 0.83 Ar_2 (30, 1500 ev) Ar_3 (30, 1000 ev) Ar_4 (30, 500 ev) M Ar M Si = Xe_1 (60, 1000 ev) Xe_3 (30, 1000 ev) Xe_5 (0, 1000 ev) M Xe M Ti = 2.74 Xe_2 (30, 1500 ev) Xe_3 (30, 1000 ev) Xe_4 (30, 500 ev) M Xe M Si = 4, [ ] [ ] Higher amount of inert gas particles in TiO 2 films than in SiO 2 films, especially for Ar Possible reasons: - different mass ratio of interacting particles - binary Rutherford scattering becomes less important C. Bundesmann, et al., Appl. Surf. Sci., in presss, DOI: /j.apsusc

13 Film properties 13 Optical properties (SE) Ion incidence angle varied Emission angle varied Cauchy model: n λ = A n + B n λ 2 + C n λ 4 Index of refraction (and A n ) almost constant Barely affected by ion species and ion incidence angle

14 n n Film properties 14 Optical properties (SE) (a) TiO 2 SiO 2 Ar_1 (60, 1000 ev) = 0 = 20 = 40 = 60 = 80 Refractive index of SiO 2 Smaller changes 2.3 than for TiO (b) Xe_1 (60, 1000 ev) = 0 = 20 = 40 = 60 = [nm] C. Bundesmann, et al., Nucl. Instrum. Methods Phys. Res., Sect. B, 395 (2017) 17.

15 Comparison Optical properties 15 Optical properties (SE) TiO 2 SiO 2 Refractive index of SiO 2 Smaller changes than for TiO 2 probably caused by smaller variation in mass density γ [º] C. Bundesmann, et al., Nucl. Instrum. Methods Phys. Res., Sect. B, 395 (2017) 17.

16 The end 16 Summary and outlook Film properties of SiO 2 depend systematically on process parameters: surface roughness, composition, optical properties Mainly influenced by scattering geometry; impact of ion energy and ion species is rather small Results show similar systematics as TiO 2 films, but variations are much smaller Differences may be caused by lower mass density variations of SiO 2 Further film properties (XRR, XRD, ) mass density, structure Properties of secondary particles (ESMS) Applications: e.g. amorphous Ti x Si 1-x O 2 films for waveguide or photonic devices

17 The end 17 Acknowledgments Prof. Dr. Dr. h.c. B. Rauschenbach A. Finzel, F. Frost, J.W. Gerlach, F. Scholze, R. Woyciechowski (all IOM) IOM workshop Financial support: DFG (project BU2625/1-2)

18 The end 18 Thank you for your attention!