On the electrical asymmetry effect in large area multiple frequency capacitively coupled plasmas

Bienholz, Stefan; Styrnoll, Tim; Awakowicz, Peter

doi:10.1088/0022-3727/47/6/065201

Cited by 35 publications

(36 citation statements)

References 22 publications

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“…The ion flux is comparatively insensitive to the change in the phase shift meaning that the two quantities can be controlled independently of one another. Since the original study many investigations have demonstrated this effect through both simulation and experiment and extended it to the use of more than two frequencies to increase the amplitude asymmetry of the waveform [28][29][30][31][32][33][34][35][36][37][38][39][40][41]. It has also been demonstrated that an electrical asymmetry can be generated using sawtooth-like waveforms where the rise and fall times of the voltage waveform differ [41][42][43][44][45][46][47][48].…”

Section: Introductionmentioning

confidence: 97%

Controlling plasma properties under differing degrees of electronegativity using odd harmonic dual frequency excitation

Gibson

Gans

2017

Plasma Sources Sci. Technol.

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The charged particle dynamics in low-pressure oxygen plasmas excited by odd harmonic dual frequency waveforms (low frequency of 13.56 MHz and high frequency of 40.68 MHz) are investigated using a one-dimensional numerical simulation in regimes of both low and high electronegativity. In the low electronegativity regime, the time and space averaged electron and negative ion densities are approximately equal and plasma sustainment is dominated by ionisation at the sheath expansion for all combinations of low and high frequency and the phase shift between them. In the high electronegativity regime, the negative ion density is a factor of 15-20 greater than the low electronegativity cases. In these cases, plasma sustainment is dominated by ionisation inside the bulk plasma and at the collapsing sheath edge when the contribution of the high frequency to the overall voltage waveform is low. As the high frequency component contribution to the waveform increases, sheath expansion ionisation begins to dominate. It is found that the control of the average voltage drop across the plasma sheath and the average ion flux to the powered electrode are similar in both regimes of electronegativity, despite the differing electron dynamics using the considered dual frequency approach. This offers potential for similar control of ion dynamics under a range of process conditions, independent of the electronegativity. This is in contrast to ion control offered by electrically asymmetric waveforms where the relationship between the ion flux and ion bombardment energy is dependent upon the electronegativity.

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Section: Introductionmentioning

confidence: 97%

Controlling plasma properties under differing degrees of electronegativity using odd harmonic dual frequency excitation

Gibson

Gans

2017

Plasma Sources Sci. Technol.

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“…8,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] The individual voltage drops across the plasma-electrode sheaths can be customized within the fundamental RF period, resulting in control of the ion and electron heating dynamics on a nanosecond time scale. Furthermore, this approach allows control of the symmetry of the discharge, which translates into a convenient method of tuning the mean ion energy at both the powered and the grounded electrodes.…”

Section: Introductionmentioning

confidence: 99%

Power supply and impedance matching to drive technological radio-frequency plasmas with customized voltage waveforms

Franek

Brandt

Berger

et al. 2015

Review of Scientific Instruments

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We present a novel radio-frequency (RF) power supply and impedance matching to drive technological plasmas with customized voltage waveforms. It is based on a system of phase-locked RF generators that output single frequency voltage waveforms corresponding to multiple consecutive harmonics of a fundamental frequency. These signals are matched individually and combined to drive a RF plasma. Electrical filters are used to prevent parasitic interactions between the matching branches. By adjusting the harmonics' phases and voltage amplitudes individually, any voltage waveform can be approximated as a customized finite Fourier series. This RF supply system is easily adaptable to any technological plasma for industrial applications and allows the commercial utilization of process optimization based on voltage waveform tailoring for the first time. Here, this system is tested on a capacitive discharge based on three consecutive harmonics of 13.56 MHz. According to the Electrical Asymmetry Effect, tuning the phases between the applied harmonics results in an electrical control of the DC self-bias and the mean ion energy at almost constant ion flux. A comparison with the reference case of an electrically asymmetric dual-frequency discharge reveals that the control range of the mean ion energy can be significantly enlarged by using more than two consecutive harmonics.

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“…A more recent approach, based on the Electrical Asymmetry Effect (EAE) [10][11][12][13][14][15][16][17][18][19][20][21][22][23] makes use of the generation of a controllable DC self-bias that develops even in geometrically symmetric reactors when the discharge is excited by the sum of two (or more) consecutive harmonics of a base frequency. The control over the DC self-bias, η, and over the mean ion energy by changing the phase angles of the applied harmonics has been confirmed both experimentally [11][12][13] and in simulations [13][14][15][16][17][18][19], and has been proven benefitial in thin film deposition applications [20][21][22][23]. While these basic approaches and their variants [24] allow controlling these two integral characteristics of the ion flux-energy distribution function (IDF), a control over the shape of the IDF would be highly desirable, e.g.…”

Section: Introductionmentioning

confidence: 99%

Customized ion flux-energy distribution functions in capacitively coupled plasmas by voltage waveform tailoring

Schüngel

Hartmann

Derzsi

et al. 2015

Plasma Sources Sci. Technol.

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Abstract. We propose a method to generate a single peak at a distinct energy in the ion flux-energy distribution function (IDF) at the electrode surfaces in capacitively coupled plasmas. The technique is based on the tailoring of the driving voltage waveform, i.e. adjusting the phases and amplitudes of the applied harmonics, to optimize the accumulation of ions created by charge exchange collisions and their subsequent acceleration by the sheath electric field. The position of the peak (i.e. the ion energy) and the flux of the ions within the peak of the IDF can be controlled in a wide domain by tuning the parameters of the applied RF voltage waveform, allowing optimization of various applications where surface reactions are induced at particular ion energies.

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On the electrical asymmetry effect in large area multiple frequency capacitively coupled plasmas

Cited by 35 publications

References 22 publications

Controlling plasma properties under differing degrees of electronegativity using odd harmonic dual frequency excitation

Controlling plasma properties under differing degrees of electronegativity using odd harmonic dual frequency excitation

Power supply and impedance matching to drive technological radio-frequency plasmas with customized voltage waveforms

Customized ion flux-energy distribution functions in capacitively coupled plasmas by voltage waveform tailoring

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