r-HIPIMS of magnesium oxide F. Moens, S. Konstantinidis, D. Depla - - PDF document

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r-HIPIMS of magnesium oxide F. Moens, S. Konstantinidis, D. Depla - - PDF document

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r-HIPIMS of magnesium oxide F. Moens, S. Konstantinidis, D. Depla Dedicated Research on Advanced Films and Targets Ghent University Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

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SLIDE 1

r-HIPIMS of magnesium oxide

  • F. Moens, S. Konstantinidis, D. Depla

Dedicated Research on Advanced Films and Targets Ghent University

  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Introduction

  • Parameters influencing hysteresis behavior in D.C. sputtering
  • Sputter yield
  • Electron Yield
  • Influence of these parameters for HiPIMS experiments
  • Influence of target erosion on the I-V characteristics
  • Influence of secondary electron yield on I-V characteristics
  • r-HiPIMS of Mg

1 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

slide-2
SLIDE 2
  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Magnesium oxide: DC magnetron sputtering

  • 30 sccm Ar
  • 0.5 Pa Ar pressure
  • Pronounced hysteresis
  • 0.2 A constant current
  • Large difference in sputter yield

2 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Magnesium oxide: DC magnetron sputtering

  • 30 sccm Ar
  • 0.5 Pa Ar pressure
  • Pronounced hysteresis
  • 0.2 A constant current
  • Large difference in sputter yield
  • Large difference in SEY

3 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

slide-3
SLIDE 3
  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

High sputter rate– Erosion of the target

N S N S N S

Target erosion

4 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

High sputter rate–Erosion of the target–Deposition rate

W0 : effective ionisation energy i : ion collection efficiency (for magnetron : almost 1) 0 : fraction of maximum possible number of ions (for magnetron : almost 1) m : multiplication factor : accounts for ionisation in the sheath f : effective ionisation probability : influenced by electron recapture ISEE : ion induced secondary electron emission yield

  • G. Buyle, “Simplified model for the DC planar magnetron discharge

PhD Dissertation, UGENT,2005

  • D. Depla et al. J. Appl. Phys. 101 (2007) 013301/1-013301/9

Depla D. et al. SCT 200 (2006) 4329 -4338

5 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

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SLIDE 4
  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

High sputter rate–Erosion of the target– I-V

  • Current increases more

rapidly for higher voltages

  • More closed magnetic field

lines

  • More electrons in sheath
  • More ionization
  • Effective secondary

electron yield increases

  • Similar to low density

discharge Capek et al.[1]

[1]Čapek, J., Hála, M., Zabeida, O., Klemberg-Sapieha, J. E., & Martinu, L. (2012). Steady state discharge optimization in high-power impulse magnetron sputtering through the control of the magnetic field. Journal of Applied Physics, 111(2), 023301.

6 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

High sputter rate– Erosion of the target – I-V

  • Mg eroded at a controlled way
  • -600 V
  • Peak current increases due to increased effective secondary electron yield

7 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

slide-5
SLIDE 5
  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

High sputter rate–Erosion of the target – I-V

  • Mg eroded at a controlled way
  • -600 V
  • Peak current increases due to increased effective secondary electron yield

8 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

High sputter rate–Erosion of the target– I-V

  • Mg eroded at a controlled way
  • -600 V
  • Peak current increases due to increased effective secondary electron yield
  • Good correlation with peak current

9 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

slide-6
SLIDE 6
  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Comparison with Cr

  • Cr also current increase due to erosion track formation
  • Different values due to material dependent secondary electron yield
  • Pressure increased to 1.8 Pa to investigate 17 different materials at -500 V

10 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Secondary electron yield

  • Different values due to material dependent secondary electron yield
  • Pressure increased to 1.8 Pa to investigate 17 different materials at -500 V

11 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

slide-7
SLIDE 7
  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Secondary electron yield

  • 2
  • Momentum transfer

Secondary electron yield 4 · · ² Energy transfer function: Average energy sputtered particle[1]: 2

  • [1] Eckstein, W., ENERGY-DISTRIBUTIONS OF SPUTTERED PARTICLES. Nuclear

Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms, 1987. 18(4-6):p. 344-348.

Sputter yield: Y

12 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Secondary electron yield

  • A correlation of peak

current

  • Pb large ionization cross

section

  • Ag, Cu and Zn:

below DC limit

  • Without Ag, Cu an Zn

still good and unchanged correlation

  • Connects rarefaction in

DC with HiPIMS

13 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

slide-8
SLIDE 8
  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Power limited poisoning experiment

  • Secondary electron yield difference Mg and MgO: 0.16 vs 0.4
  • Arcing when we try to do a classical D.C. hysteresis
  • Solution constant power experiments
  • 80 W limit

14 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Power limited poisoning experiment

  • Increasing duty cycle from 0.99 % to 2.91 %
  • First critical point shifts to higher O flows
  • Increase in duty cycle  increased current

 lower voltage

15 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

slide-9
SLIDE 9
  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Power limited poisoning experiment

  • Increasing duty cycle from 0.99 % to 2.91 %
  • First critical point shifts to higher O flows
  • Increase in duty cycle  increased current

 lower voltage

16 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

I-V curve at constant oxygen flow

  • We start a metallic discharge at 1000 V
  • Ad oxygen flow (in this experiment 0.6 SCCM)
  • Lower the voltage  lower current current due to metallic I(V)

 Less sputter cleaning  Target gets poisoned by the oxygen flow Transition Metallic I(V) Poisoned I(V)

17 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

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SLIDE 10
  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

I-V curve at constant oxygen flow

  • Erosion
  • Effective secondary electron yield is increased
  • More sputtering at the same voltage
  • Transition at lower voltages

Transition Metallic I(V) Poisoned I(V)

18 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Increasing the voltage

  • Increasing the voltage  reverse process is expected
  • Transition regime overlaps the metallic regime
  • Can’t be explained by erosion

19 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

slide-11
SLIDE 11
  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Increasing the voltage vs constant power

Explains change in discharge voltage

20 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Voltage hysteresis – oxygen flow

  • Low values of oxygen flow
  • Transition to poisoned regime shifts to discharge voltages too low to sustain

the plasma

  • The extended transition

21 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

slide-12
SLIDE 12
  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Voltage hysteresis – oxygen flow

  • Higher current in the transition region
  • Arcing
  • Power limitations

22 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Increasing the voltage

  • Increasing the voltage  reverse process is expected
  • Transition regime overlaps the metallic regime
  • Can’t be explained by erosion

23 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

slide-13
SLIDE 13
  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Voltage hysteresis – oxygen flow

  • Higher oxygen flow

 transition shifts to higher voltages

  • Location of minimum is

most prone to erosion

24 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Increasing the voltage

  • Increasing the voltage  reverse process is expected
  • Transition regime overlaps the metallic regime
  • Can’t be explained by erosion

25 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

slide-14
SLIDE 14
  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Voltage hysteresis – oxygen flow

  • Higher oxygen flow

 transition shifts to higher voltages

  • Location of minimum is

most prone to erosion

  • Current of transition at

600V

26 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO

  • F. Moens

HIPIMS 2017 www.DRAFT.ugent.be

Conclusion and Acknowledgements

  • DC magnetron sputtering current controlled HiPIMS voltage controlled
  • High sputter yield gives rise to changes in I(V)
  • High secondary electron yield gives steep I(V) for poisoned target
  • Extended transition region

27 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO