Electron power absorption dynamics in capacitive radio frequency discharges driven by tailored voltage waveforms in CF4

The power absorption dynamics of electrons and the electrical asymmetry effect in capacitive radio-frequency plasmas operated in CF4 and driven by tailored voltage waveforms are investigated experimentally in combination with kinetic simulations. The driving voltage waveforms are generated as a superposition of multiple consecutive harmonics of the fundamental frequency of 13.56 MHz. Peaks/valleys and sawtooth waveforms are used to study the effects of amplitude and slope asymmetries of the driving voltage waveform on the electron dynamics and the generation of a DC self-bias in an electronegative plasma at different pressures. Compared to electropositive discharges, we observe strongly different effects and unique power absorption dynamics. At high pressures and high electronegativities, the discharge is found to operate in the drift-ambipolar (DA) heating mode. A dominant excitation/ionization maximum is observed during sheath collapse at the edge of the sheath which collapses fastest. High negative-ion densities are observed inside this sheath region, while electrons are confined for part of the RF period in a potential well formed by the ambipolar electric field at this sheath edge and the collapsed (floating potential) sheath at the electrode. For specific driving voltage waveforms, the plasma becomes divided spatially into two different halves of strongly different electronegativity. This asymmetry can be reversed electrically by inverting the driving waveform. For sawtooth waveforms, the discharge asymmetry and the sign of the DC self-bias are found to reverse as the pressure is increased, due to a transition of the electron heating mode from the α-mode to the DA-mode. These effects are interpreted with the aid of the simulation results.

[1]  J. Booth,et al.  Controlling the shape of the ion energy distribution at constant ion flux and constant mean ion energy with tailored voltage waveforms , 2016 .

[2]  D. J. Economou,et al.  Effect of gas properties on the dynamics of the electrical slope asymmetry effect in capacitive plasmas: comparison of Ar, H2 and CF4 , 2016 .

[3]  B. Bora.  Corrigendum: Studies on the effect of finite geometrical asymmetry in dual capacitively coupled radio frequency plasma (2015 Plasma Sources Sci. Technol. 24 054002) , 2015 .

[4]  B. Bora.  Effect of driving voltages in dual capacitively coupled radio frequency plasma: A study by nonlinear global model , 2015 .

[5]  B. Bora.  Studies on the effect of finite geometrical asymmetry in dual capacitively coupled radio frequency plasma , 2015 .

[6]  J. Schulze,et al.  Electron heating via self-excited plasma series resonance in geometrically symmetric multi-frequency capacitive plasmas , 2015, 1602.03853.

[7]  P. Hartmann,et al.  Customized ion flux-energy distribution functions in capacitively coupled plasmas by voltage waveform tailoring , 2015, 1602.02624.

[8]  Andrew Gibson,et al.  Influence of surface conditions on plasma dynamics and electron heating in a radio-frequency driven capacitively coupled oxygen plasma , 2015 .

[9]  Andrew Gibson,et al.  Erratum: “Tailoring the nonlinear frequency coupling between odd harmonics for the optimisation of charged particle dynamics in capacitively coupled oxygen plasmas” [Appl. Phys. Lett. 106, 054102 (2015)] , 2015 .

[10]  You-nian Wang,et al.  Heating mode transition in capacitively coupled CF4 discharges: comparison of experiments with simulations , 2015 .

[11]  E. Schüngel,et al.  Power supply and impedance matching to drive technological radio-frequency plasmas with customized voltage waveforms. , 2015, The Review of scientific instruments.

[12]  J. Schulze,et al.  On the self-excitation mechanisms of plasma series resonance oscillations in single- and multi-frequency capacitive discharges , 2015, 1602.03482.

[13]  J. Booth,et al.  Strong ionization asymmetry in a geometrically symmetric radio frequency capacitively coupled plasma induced by sawtooth voltage waveforms. , 2015, Physical review letters.

[14]  U. Czarnetzki,et al.  Prevention of ion flux lateral inhomogeneities in large area capacitive radio frequency plasmas via the electrical asymmetry effect , 2015 .

[15]  W. Graham,et al.  Tailoring the nonlinear frequency coupling between odd harmonics for the optimisation of charged particle dynamics in capacitively coupled oxygen plasmas , 2015 .

[16]  J. Röpcke,et al.  Evaluation of the Electrical Asymmetry Effect by spectroscopic measurements of capacitively coupled discharges and silicon thin film depositions , 2015 .

[17]  J. Booth,et al.  Control and optimization of the slope asymmetry effect in tailored voltage waveforms for capacitively coupled plasmas , 2014 .

[18]  J. Booth,et al.  Ion flux asymmetry in radiofrequency capacitively-coupled plasmas excited by sawtooth-like waveforms , 2014 .

[19]  D. J. Economou,et al.  Radio-frequency capacitively coupled plasmas in hydrogen excited by tailored voltage waveforms: comparison of simulations with experiments , 2014 .

[20]  J. Schulze,et al.  The effect of ambipolar electric fields on the electron heating in capacitive RF plasmas , 2014, 1602.01719.

[21]  D. Coumou,et al.  Ion Energy Distribution Skew Control Using Phase-Locked Harmonic RF Bias Drive , 2014, IEEE Transactions on Plasma Science.

[22]  You-nian Wang,et al.  Heating mode transition in a hybrid direct current/dual-frequency capacitively coupled CF4 discharge , 2014 .

[23]  M. Kushner,et al.  Control of ion energy distributions using phase shifting in multi-frequency capacitively coupled plasmas , 2014, 2014 IEEE 41st International Conference on Plasma Sciences (ICOPS) held with 2014 IEEE International Conference on High-Power Particle Beams (BEAMS).

[24]  J. Booth,et al.  Electron heating in capacitively coupled plasmas revisited , 2014 .

[25]  E. Schüngel,et al.  Complex Electron Heating in Capacitive Multi-Frequency Plasmas , 2014, IEEE Transactions on Plasma Science.

[26]  P. Awakowicz,et al.  On the electrical asymmetry effect in large area multiple frequency capacitively coupled plasmas , 2014 .

[27]  J. Schulze,et al.  Electron heating and control of ion properties in capacitive discharges driven by customized voltage waveforms , 2013, 2014 IEEE 41st International Conference on Plasma Sciences (ICOPS) held with 2014 IEEE International Conference on High-Power Particle Beams (BEAMS).

[28]  J. Booth,et al.  Capacitively coupled radio-frequency plasmas excited by tailored voltage waveforms , 2013 .

[29]  Vincent M. Donnelly,et al.  Plasma etching: Yesterday, today, and tomorrow , 2013 .

[30]  R. Schneider,et al.  Observation of Ω mode electron heating in dusty argon radio frequency discharges , 2013 .

[31]  U. Czarnetzki,et al.  The effect of dust on electron heating and dc self-bias in hydrogen diluted silane discharges , 2013 .

[32]  C. Chung,et al.  Collisionless electron heating by radio frequency bias in low gas pressure inductive discharge , 2012 .

[33]  U. Czarnetzki,et al.  Fundamental investigations of capacitive radio frequency plasmas: simulations and experiments , 2012 .

[34]  J. Meichsner,et al.  Dynamics and Electronegativity of Oxygen RF Plasmas , 2012 .

[35]  T. Gans,et al.  Tailoring electron energy distribution functions through energy confinement in dual radio-frequency driven atmospheric pressure plasmas , 2012 .

[36]  M. Kushner,et al.  Control of electron energy distributions and plasma characteristics of dual frequency, pulsed capacitively coupled plasmas sustained in Ar and Ar/CF4/O2 , 2012 .

[37]  J. Booth,et al.  Separate control of the ion flux and ion energy in capacitively coupled radio-frequency discharges using voltage waveform tailoring , 2012 .

[38]  U. Czarnetzki,et al.  The electrical asymmetry effect in geometrically asymmetric capacitive radio frequency plasmas , 2012 .

[39]  S. Pouliquen,et al.  Hydrogenated microcrystalline silicon thin films deposited by RF-PECVD under low ion bombardment energy using voltage waveform tailoring , 2012 .

[40]  J. Schulze,et al.  Ionization by bulk heating of electrons in capacitive radio frequency atmospheric pressure microplasmas , 2012, 1208.6519.

[41]  J. Booth,et al.  Microcrystalline silicon solar cells deposited using a plasma process excited by tailored voltage waveforms , 2012 .

[42]  U. Czarnetzki,et al.  Coupling effects in inductive discharges with radio frequency substrate biasing , 2012 .

[43]  J. Schulze,et al.  Ionization by drift and ambipolar electric fields in electronegative capacitive radio frequency plasmas. , 2011, Physical review letters.

[44]  J. Bang,et al.  Effects of RF bias power on electron energy distribution function and plasma uniformity in inductively coupled argon plasma , 2011 .

[45]  J. Schulze,et al.  Electron heating and the electrical asymmetry effect in dual-frequency capacitive CF4 discharges , 2011 .

[46]  U. Czarnetzki,et al.  The electrical asymmetry effect in multi-frequency capacitively coupled radio frequency discharges , 2011 .

[47]  U. Czarnetzki,et al.  Power absorption in electrically asymmetric dual frequency capacitive radio frequency discharges , 2011 .

[48]  U. Czarnetzki,et al.  The electrical asymmetry effect in capacitively coupled radio-frequency discharges , 2011 .

[49]  D. Voloshin,et al.  Two modes of capacitively coupled rf discharge in CF4 , 2010 .

[50]  A. Wendt,et al.  Tailored ion energy distributions at an rf-biased plasma electrode , 2010 .

[51]  R. Schneider,et al.  Excitation Mechanisms and Sheath Dynamics in Capacitively Coupled Radio‐Frequency Oxygen Plasmas , 2010 .

[52]  J. Vanel,et al.  Nanocrystalline silicon film growth morphology control through RF waveform tailoring , 2010 .

[53]  P. Hartmann,et al.  The effect of secondary electrons on the separate control of ion energy and flux in dual-frequency capacitively coupled radio frequency discharges , 2010 .

[54]  U. Czarnetzki,et al.  Excitation dynamics in electrically asymmetric capacitively coupled radio frequency discharges: experiment, simulation, and model , 2010 .

[55]  V. Schulz-von der Gathen,et al.  The challenge of revealing and tailoring the dynamics of radio-frequency plasmas , 2010 .

[56]  T. Gans,et al.  Nonlinear frequency coupling in dual radio-frequency driven atmospheric pressure plasmas , 2010 .

[57]  U. Czarnetzki,et al.  Phase resolved optical emission spectroscopy: a non-intrusive diagnostic to study electron dynamics in capacitive radio frequency discharges , 2010 .

[58]  U. Czarnetzki,et al.  Different modes of electron heating in dual-frequency capacitively coupled radio frequency discharges , 2009 .

[59]  U. Czarnetzki,et al.  The electrical asymmetry effect in capacitively coupled radio frequency discharges – measurements of dc self bias, ion energy and ion flux , 2009 .

[60]  R. Basner,et al.  Electron stochastic heating in a capacitively coupled low-pressure argon rf-discharge , 2009 .

[61]  U. Czarnetzki,et al.  The Electrical Asymmetry Effect - A novel and simple method for separate control of ion energy and flux in capacitively coupled RF discharges , 2009 .

[62]  J Schulze,et al.  The Electrical Asymmetry Effect - A novel and simple method for separate control of ion energy and flux in capacitively coupled RF discharges , 2009 .

[63]  Zoltan Donko,et al.  PIC simulations of the separate control of ion flux and energy in CCRF discharges via the electrical asymmetry effect , 2009 .

[64]  U. Czarnetzki,et al.  Stochastic heating in asymmetric capacitively coupled RF discharges , 2008 .

[65]  P. Awakowicz,et al.  The role of the relative voltage and phase for frequency coupling in a dual-frequency capacitively coupled plasma , 2008 .

[66]  U. Czarnetzki,et al.  On the possibility of making a geometrically symmetric RF-CCP discharge electrically asymmetric , 2008 .

[67]  U. Czarnetzki,et al.  Electric field reversals in the sheath region of capacitively coupled radio frequency discharges at different pressures , 2008 .

[68]  N. Gomathi,et al.  RF plasma-treated polymers for biomedical applications , 2008 .

[69]  Jung-hyung Kim,et al.  The effects of radio-frequency bias on electron density in an inductively coupled plasma reactor , 2007 .

[70]  David Tskhakaya,et al.  Particle in Cell Simulation of Low Temperature Laboratory Plasmas , 2007 .

[71]  A. Ellingboe,et al.  Space and phase resolved plasma parameters in an industrial dual-frequency capacitively coupled radio-frequency discharge , 2007 .

[72]  R. Faulkner,et al.  Frequency coupling in dual frequency capacitively coupled radio-frequency plasmas , 2006 .

[73]  V. Zhaunerchyk,et al.  The dissociative recombination of fluorocarbon ions III: CF+2 and CF+3 , 2006 .

[74]  T. Makabe,et al.  Plasma Electronics: Applications in Microelectronic Device Fabrication , 2006 .

[75]  J. Verboncoeur.  Particle simulation of plasmas: review and advances , 2005 .

[76]  L. Alves,et al.  Systematic characterization of low-pressure capacitively coupled hydrogen discharges , 2004 .

[77]  A. Bogaerts,et al.  Numerical investigation of ion-energy-distribution functions in single and dual frequency capacitively coupled plasma reactors. , 2004, Physical review. E, Statistical, nonlinear, and soft matter physics.

[78]  A. Bogaerts,et al.  Numerical study of Ar/CF4/N2 discharges in single- and dual-frequency capacitively coupled plasma reactors , 2003 .

[79]  J. Rath,et al.  Low temperature polycrystalline silicon: a review on deposition, physical properties and solar cell applications , 2003 .

[80]  A. Bogaerts,et al.  Particle-in-cell/Monte Carlo simulation of a capacitively coupled radio frequency Ar/CF4 discharge: Effect of gas composition , 2003 .

[81]  Junying Chen,et al.  Plasma-surface modification of biomaterials , 2002 .

[82]  D. Vender,et al.  Collisionless electron heating by capacitive rf sheaths. , 2001, Physical review letters.

[83]  T. Makabe,et al.  Transport coefficients and scattering cross-sections for plasma modelling in CF4-Ar mixtures: a swarm analysis , 2000 .

[84]  K. Nanbu,et al.  Probability theory of electron-molecule, ion-molecule, molecule-molecule, and Coulomb collisions for particle modeling of materials processing plasmas and cases , 2000 .

[85]  K. Nanbu,et al.  Self-Consistent Particle Simulation of Radio Frequency CF4Discharge: Effect of Gas Pressure , 2000 .

[86]  Kazuki Denpoh Kazuki Denpoh,et al.  Self-Consistent Particle Simulation of Radio Frequency CF4 Discharge: Effect of Gas Pressure , 2000 .

[87]  U. Czarnetzki,et al.  Space and time resolved electric field measurements in helium and hydrogen RF-discharges , 1999 .

[88]  Michael A. Lieberman,et al.  From Fermi acceleration to collisionless discharge heating , 1998 .

[89]  K. Nanbu,et al.  Monte Carlo Collision Simulation of Positive-Negative Ion Recombination for a Given Rate Constant , 1998 .

[90]  C. Mahony,et al.  Sheath dynamics observed in a 13.56 MHz-driven plasma , 1997 .

[91]  D. Brewis.  Plasma surface modification , 1997 .

[92]  J. Roberts,et al.  Time‐resolved Balmer‐alpha emission from fast hydrogen atoms in low pressure, radio‐frequency discharges in hydrogen , 1995 .

[93]  R. Bonham.  Electron Impact Cross Section Data for Carbon Tetrafluoride. , 1994 .

[94]  J. Boeuf,et al.  Transition from a capacitive to a resistive regime in a silane radio frequency discharge and its possible relation to powder formation , 1992 .

[95]  T. Makabe,et al.  Study of the structure of radio frequency glow discharges in CH4 and H2 by spatiotemporal optical emission spectroscopy , 1992 .

[96]  A. Viggiano,et al.  Chemistry of CFn+ (n = 1-3) ions with halocarbons , 1992 .

[97]  J. Perrin,et al.  Spatially resolved optical emission and electrical properties of SiH4 RF discharges at 13.56 MHz in a symmetric parallel-plate configuration , 1991 .

[98]  Charles K. Birdsall,et al.  Particle-in-cell charged-particle simulations, plus Monte Carlo collisions with neutral atoms, PIC-MCC , 1991 .

[99]  Graves,et al.  Electron acoustic waves in capacitively coupled, low-pressure rf glow discharges. , 1991, Physical review letters.

[100]  T. Makabe,et al.  Study of the structure in rf glow discharges in SiH4/H2 by spatiotemporal optical emission spectroscopy: Influence of negative ions , 1990 .

[101]  R. Boswell,et al.  Numerical modeling of low-pressure RF plasmas , 1990 .

[102]  M. Lieberman,et al.  Bias voltage in finite length, cylindrical and coaxial radio‐frequency discharges , 1990 .

[103]  Boeuf,et al.  Transition between different regimes of rf glow discharges. , 1990, Physical review. A, Atomic, molecular, and optical physics.

[104]  J. Coburn,et al.  Positive‐ion bombardment of substrates in rf diode glow discharge sputtering , 1972 .