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 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 HIPIMS 2017 1 F. Moens www.DRAFT.ugent.be
Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO Magnesium oxide: DC magnetron sputtering • 30 sccm Ar • 0.2 A constant current • 0.5 Pa Ar pressure • Large difference in sputter yield • Pronounced hysteresis F. Moens HIPIMS 2017 www.DRAFT.ugent.be 2 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO Magnesium oxide: DC magnetron sputtering • 30 sccm Ar • 0.2 A constant current • 0.5 Pa Ar pressure • Large difference in sputter yield • Pronounced hysteresis • Large difference in SEY HIPIMS 2017 3 F. Moens www.DRAFT.ugent.be
Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO High sputter rate– Erosion of the target Target erosion S N S N S N F. Moens HIPIMS 2017 www.DRAFT.ugent.be 4 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO High sputter rate–Erosion of the target–Deposition rate W 0 : 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 HIPIMS 2017 5 F. Moens www.DRAFT.ugent.be
Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO 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. F. Moens HIPIMS 2017 www.DRAFT.ugent.be 6 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO 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 HIPIMS 2017 7 F. Moens www.DRAFT.ugent.be
Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO 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 F. Moens HIPIMS 2017 www.DRAFT.ugent.be 8 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO 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 HIPIMS 2017 9 F. Moens www.DRAFT.ugent.be
Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO 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 F. Moens HIPIMS 2017 www.DRAFT.ugent.be 10 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO 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 HIPIMS 2017 11 F. Moens www.DRAFT.ugent.be
Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO Secondary electron yield Momentum transfer Secondary electron yield Energy transfer function: � � 4 · � �� · � � �� �� �� � �² Average energy sputtered particle [1] : � ��� � 2� � �� � ��� � � Sputter yield: Y � 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. F. Moens HIPIMS 2017 www.DRAFT.ugent.be 12 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO 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 HIPIMS 2017 13 F. Moens www.DRAFT.ugent.be
Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO 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 F. Moens HIPIMS 2017 www.DRAFT.ugent.be 14 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO 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 HIPIMS 2017 15 F. Moens www.DRAFT.ugent.be
Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO 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 F. Moens HIPIMS 2017 www.DRAFT.ugent.be 16 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO 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 Poisoned I(V) Transition Metallic I(V) HIPIMS 2017 17 F. Moens www.DRAFT.ugent.be
Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO I-V curve at constant oxygen flow • Erosion • Effective secondary electron yield is increased • More sputtering at the same voltage • Transition at lower voltages Poisoned I(V) Transition Metallic I(V) F. Moens HIPIMS 2017 www.DRAFT.ugent.be 18 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO Increasing the voltage • Increasing the voltage reverse process is expected • Transition regime overlaps the metallic regime • Can’t be explained by erosion HIPIMS 2017 19 F. Moens www.DRAFT.ugent.be
Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO Increasing the voltage vs constant power Explains change in discharge voltage F. Moens HIPIMS 2017 www.DRAFT.ugent.be 20 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO 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 HIPIMS 2017 21 F. Moens www.DRAFT.ugent.be
Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO Voltage hysteresis – oxygen flow • Higher current in the transition region • Arcing • Power limitations F. Moens HIPIMS 2017 www.DRAFT.ugent.be 22 Introduction Hysteresis during D.C. HiPIMS: Erosion of the target Secondary ellectron yield r-HiPIMS of MgO Increasing the voltage • Increasing the voltage reverse process is expected • Transition regime overlaps the metallic regime • Can’t be explained by erosion HIPIMS 2017 23 F. Moens www.DRAFT.ugent.be
Recommend
More recommend
