High Power Impulse Magnetron Sputtering: a Tool for Synthesizing New Functional Thin Films and Coatings

Transcription

1 High Power Impulse Magnetron Sputtering: a Tool for Synthesizing New Functional Thin Films and Coatings Dr. Kostas Sarakinos (Linköping University, Švédsko ) The project is co-financed by the European Social Fund and the state budget of the Czech Republic.

2 HiPIMS: a tool for synthesizing functional thin films and coatings Kostas Sarakinos (kostas@ifm.liu.se) Plasma & Coatings Physics Division, Linköping University, Linköping, Sweden (

3 Our research concept Atomistic Growth Mechanisms Functional films and nanomaterials Innovative Processes Plasma Fundamentals 3

4 The film growth Thermodynamics Kinetics Chemical environment Geometrical constrains Energy of film forming species [Petrov et al., J. Vac. Sci. Technol. A21 (2003) 118] 4

5 Providing energy to the growing film [ 5

6 Ions and plasma-assisted PVD Conventional magnetron sputtering [J.A. Hopwood, in: J.A. Hopwood (Ed.), Thin Films: Ionized Physical Vapor Deposition, Academic Press, San Diego, 2000, p. 181.] 6

7 The challenge? Ar + Ar + M M M M + M + M + to turn a conventional magnetron source into an ion source 7

8 The HiPIMS principle High peak target power density high plasma (electron) density? [Kouznetsov et al., Surf. Coat. Technol. 122 (1999) 290] 8

9 The HiPIMS process: Ionization [Bohlmark et al., J. Vac. Sci. Technol. A 23 (2005) 18] 9

10 The HiPIMS process: Gasless sputtering [Andersson and Anders, Appl. Phys. Lett. 92 (2008) ] 10

11 The HiPIMS process: Ion energy dcms HiPIMS [Bohlmark et al., Thin Solid Films 515 (2006) 1522] 11

12 The HiPIMS process: Ion transport [Lundin et al., Plasma Sources. Sci. Technol. 17 (2008) ] 12

13 The HiPIMS process: Reactive deposition [Wallin and Helmersson, Thin Solid Films 516 (2008) 6398] [Sarakinos et al., Surf. Coat. Technol. 202 (2008) 5033] 13

14 Closing the circle Atomistic Growth Mechanisms New functional materials Innovative Processes Plasma Fundamentals 14

15 Content 1. Nanocrystalline transition metal nitride films 2. From a stable reactive HiPIMS process to high-k dielectric layers 15

16 1. Nanocrystalline transition metal nitride films 16

17 Thin film growth Chemical environment Geometrical factors Energy of film forming species [Petrov et al., J. Vac. Sci. Technol. A21 (2003) 118] Diffusion processes (surface and bulk) Structural zone models (SZM) 17

18 Elemental films-zone I (T s /T m <0.2) [Barna and Adamik, Thin Solid Films 317 (1998) 27] No diffusion 18

19 Elemental films-zone T (0.2<T s /T m <0.4) [Barna and Adamik, Thin Solid Films 317 (1998) 27] Surface diffusion 19

20 Elemental films-zone II (T s /T m >0.4) [Barna and Adamik, Thin Solid Films 317 (1998) 27] Surface and bulk diffusion 20

21 The role of impurities (the Al-O system) Suppresion of grain coarsening Addition of O Renucleation Globular microstructure (Zone III) [Barna and Adamik, Thin Solid Films 317 (1998) 27] 21

22 Particle bombardment increases the nucleation rate and changes the island size distribution. Fast Ions & Neutrals: Create preferential nucleation sites Disrupt small clusters Increase effective adatom mobilities Heat the surface Energetic bombardment [Hasan et al., J. Vac. Sci. Technol. A5, 1883 (1987)] 22

23 Generalized SZM Zone III: Result of impurities and energetic bombardment Observed at any temperature! [Barna and Adamik, Thin Solid Films 317 (1998) 27] 23

24 Renucleation in HiPIMS (CrN) dcms HiPIMS [Ehiasarian et al., Thin Solid Films 457 (2004) 270] 24

25 Control of energetic bombardment in HiPIMS Peak target current (I Tp ) Pulse-integrated I (counts) Cr dcms Cr Ar + Ar 0 Deposition at: Low energetic bombardment Various ion-to-neutral ratios Various ion current compositions I Tp (A) [Alami, Sarakinos et al., J. Phys. D: Appl. Phys. 42 (2009) ] 25

26 Effect on the film microstructure Ion irradiation Interruption of columnar growth and re-nucleation Featureless morphology [Alami, Sarakinos et al., J. Phys. D: Appl. Phys. 42 (2009) ] 26

27 Effect on the film microstructure dcms films Columnar structure Intercolumnar porosity Polycrystalline films HiPIMS films Ultra dense structure Degradation of crystallinity [Alami, Sarakinos et al., J. Phys. D: Appl. Phys. 42 (2009) ] 27

28 Take-home message Microstructure (film) HiPIMS (process) Nanocryst. M-nitrides (material) Ionization (plasma) 28

29 2. From a stable reactive HiPIMS process to high-k dielectric layers 29

30 The need for high-k gate dielectrics 30

31 HfO 2 [Zhao and Vanderbilt, Phys. Rev. B 65 (2002) ] 31

32 Stabilization of (t) and (c)- HfO 2 [Kita et al., Appl. Phys. Lett. 86 (2005) ] [Tomida et al., Appl. Phys. Lett. 89 (2006) ] Dopping of the metal sublattice (Y, Si.) 32

33 Alternative strategy for ZrO 2 dcms in Ar-O 2 -N 2 ambient: stabilization of the transition zone and the c- ZrO 2 phase N incorporation and O vacancy formation Suggestion: deposition in the transition zone lower target coverage suppression of O - bombardment c-zro 2 [Severin et al., Appl. Phys Lett., 88 (2006) ] [Severin, Sarakinos et al., J. Appl. Phys., 103 (2008) ] 33

34 Is this approach viable for HfO 2? [Sarakinos et al., J. Appl. Phys. 108 (2010) ] 34

35 What is the role of O - ions? [Severin, PhD Thesis, RWTH Aachen, Germany 2006 ] [Sarakinos et al., J. Appl. Phys. 108 (2010) ] 35

36 Phase formation without N incorporation HiPIMS/pN2 =0 [Wallin et al., Thin Solid Films 516 (2008) 6398] [Sarakinos et al., Surf. Coat. Technol. 202 (2008) 5033] [Sarakinos et al., J. Appl. Phys. 108 (2010) ] 36

37 The effect of the non-metal sublattice configuration [Sarakinos et al., J. Appl. Phys. 108 (2010) ] 37

38 Take-home message Chemical composition (film) HiPIMS & dcms (process) High-k HfO 2 phase (material) Stable process (plasma) 38

39 Your name, conference name