Ion energy control in reactive ion etching using 1-MHz pulsed-DC square-wave-superimposed 100-MHz RF capacitively coupled plasma

Ui, Akio; Hayashi, Hisataka; Sakai, Itsuko; Kaminatsui, Takeshi; Ohiwa, Tokuhisa; Yamamoto, Katsumi; Kikutani, Keisuke

doi:10.1116/1.4943384

Cited by 7 publications

(3 citation statements)

References 26 publications

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“…Ion energy can be controlled by biasing the substrate surface voltage potential with a power converter [3]- [5]. Different bias voltage waveforms have been studied, including the RF sinusoidal voltage waveform [6]- [9], pulse-shape voltage waveform [10]- [12], and tailored pulse-shaped voltage waveform [13]- [17]. For a typical dielectric substrate, the so-called tailored pulse-shaped voltage waveform has proven to be effective and promising [14], [17].…”

Section: Bulk Plasmamentioning

confidence: 99%

Auto-Tuning Control of a Switched-Mode Power Converter for Tailored Pulse-Shape Biased Plasma Etching Applications

Lemmen

Wijnands

et al. 2021

2021 IEEE Energy Conversion Congress and Exposition (ECCE)

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Section: Bulk Plasmamentioning

confidence: 99%

Auto-Tuning Control of a Switched-Mode Power Converter for Tailored Pulse-Shape Biased Plasma Etching Applications

Lemmen

Wijnands

et al. 2021

2021 IEEE Energy Conversion Congress and Exposition (ECCE)

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“…Over the past decades, several techniques have been developed, which have in common that those go beyond the single frequency symmetric voltage drive. Asymmetric tailored driving voltage waveforms can be achieved based on the combination of carefully adjusted subsequent harmonic RF components (called Fourier ansatz) [9][10][11] or by using a superposition of a single high frequency (HF) component to drive plasma generation, and a low frequency (LF) modulation signal of arbitrary shape with a repetition rate as low as 10-100 kHz to control the sheath voltage evolution [12][13][14][15][16][17][18]. In case of square-shaped voltage waveforms and in the presence of a conducting wafer, the presence of a broad plateau of the applied voltage waveform leads to the formation of a narrow peak of the IFEDF at the wafer surface at low pressure, since the sheath voltage remains constant for a large fraction of the pulse period.…”

Section: Introductionmentioning

confidence: 99%

Control of ion flux-energy distribution at dielectric wafer surfaces by low frequency tailored voltage waveforms in capacitively coupled plasmas

Hartmann

Korolov

Escandón-López

et al. 2023

J. Phys. D: Appl. Phys.

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Capacitively coupled plasmas are routinely used in an increasing number of technological applications, where a precise control of the flux and energy distribution of ions impacting boundary surfaces is required. In the presence of dielectric wafers and targets the accumulation of charges on these surfaces can significantly alter the time evolution of the sheath electric field that is accountable for ion acceleration from the plasma bulk to the surfaces and, thus, lead to parasitic distortions of process relevant ion flux-energy distributions. We apply PIC/MCC simulations to provide insights into the operation, ion acceleration mechanisms, and the formation of such distributions at dielectric wafers for discharges in argon gas. The discharges are driven by a combination of a single high frequency (27.1~MHz) voltage signal and a low frequency (100~kHz) customized pulsed voltage waveform. The low frequency waveform includes a base square signal to realize narrow and controllable high energy peaks of the ion distribution, and steady-slope ramp voltage components. We discuss the distorting effect of dielectric surface charging on the ion flux-energy distribution and provide details about how the voltage ramps can restore its narrow peaked shape. The dependence of the surface charging properties on the low frequency pulse duty cycle and amplitude, as well as the high frequency voltage amplitude is revealed. The radial homogeneity of the ion flux is found to be maintained within ± 10 % around the mean value for all quantities investigated. The radial electric field developing at the edge of the dielectric wafer with finite width has only a small influence on the overall homogeneity of the plasma across the whole surface, its effect remains localised to the outermost few mm-s of the wafer.

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“…power is inductively coupled to the plasma across a dielectric window, which yields a low plasma floating potential of typically 20 to 40 V with respect to the substrate and enables better decoupled control of ion flux and ion energy [9]. Different biasing techniques for ICPs have been studied [20][21][22], including RF biasing [23][24][25], pulse-shaped biasing [26][27][28], and tailored waveform biasing [29][30][31][32][33], the voltage waveforms of which are shown in figures 2(a)-(c), respectively. The negative parts of all the three biasing waveforms are used to create a negative voltage potential on the substrate surface to enhance ion energy.…”

Section: Introductionmentioning

confidence: 99%

Equivalent electric circuit model of accurate ion energy control with tailored waveform biasing

Lemmen

Vermulst

et al. 2022

Plasma Sources Sci. Technol.

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For atomic scale plasma processing involving precise, (an)isotropic and selective etching and deposition, it is required to precisely control the energy of the plasma ions. Tailored waveforms have been employed to bias the substrate table to accurately control this ion energy. Recent research has shown that switched-mode power converters can be used to generate this kind of waveform, with the benefit of increased energy efficiency and flexibility compared to the traditionally used linear amplifiers. In this article, an improved equivalent electric circuit model of the plasma reactor is proposed to allow simulation and bias waveform optimization. The equivalent circuit is analysed for different process phases, including the charge, discharge and post-discharge phase. The proposed model is suitable for electric circuit simulation and can be used for predicting the electric waveforms and ion energy distribution. Plasma parameters are required as input for the model, thus an empirical parameter identification method based on the electric measurements of the bias voltage and output current waveforms is introduced. Since these electrical measurements do not interact with the plasma process, the proposed parameter identification method is nonintrusive. Experiments have been carried out, which demonstrate that the proposed model and parameter identification method provide the expected accuracy.

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Ion energy control in reactive ion etching using 1-MHz pulsed-DC square-wave-superimposed 100-MHz RF capacitively coupled plasma

Cited by 7 publications

References 26 publications

Auto-Tuning Control of a Switched-Mode Power Converter for Tailored Pulse-Shape Biased Plasma Etching Applications

Auto-Tuning Control of a Switched-Mode Power Converter for Tailored Pulse-Shape Biased Plasma Etching Applications

Control of ion flux-energy distribution at dielectric wafer surfaces by low frequency tailored voltage waveforms in capacitively coupled plasmas

Equivalent electric circuit model of accurate ion energy control with tailored waveform biasing

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