Mechanisms for CF2 radical generation and loss on surfaces in fluorocarbon plasmas

Zhang, Da; Kushner, Mark J.

doi:10.1116/1.1319816

Cited by 65 publications

(20 citation statements)

References 26 publications

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“…Such processes have not yet been included in the models for C 4 F 8 reported up to now. [25][26][27]32,37…”

Section: Validation and Limitations Of The Modelmentioning

confidence: 99%

“…may play a synergic role for certain aspects of the etch process, such as polymerization, chemical etching, and physical sputtering. [35][36][37][38][39][40] Therefore, in this paper, we study in detail the dissociation and ionization mechanisms of a C 4 F 8 inductively coupled plasma (ICP) in a wide range of discharge conditions, focusing on the fragmentation structure, i.e., the total dissociation degree, the density ratios of ions vs. neutrals and of F vs. C x F y , and the fractions of various fc neutrals and ions. The structure of the paper is as follows.…”

Section: Introductionmentioning

confidence: 99%

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Bulk plasma fragmentation in a C4F8 inductively coupled plasma: A hybrid modeling study

Zhao

Zhang

Gao

et al. 2015

Journal of Applied Physics

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A hybrid model is used to investigate the fragmentation of C 4 F 8 inductive discharges. Indeed, the resulting reactive species are crucial for the optimization of the Si-based etching process, since they determine the mechanisms of fluorination, polymerization, and sputtering. In this paper, we present the dissociation degree, the density ratio of F vs. C x F y (i.e., fluorocarbon (fc) neutrals), the neutral vs. positive ion density ratio, details on the neutral and ion components, and fractions of various fc neutrals (or ions) in the total fc neutral (or ion) density in a C 4 F 8 inductively coupled plasma source, as well as the effect of pressure and power on these results. To analyze the fragmentation behavior, the electron density and temperature and electron energy probability function (EEPF) are investigated. Moreover, the main electron-impact generation sources for all considered neutrals and ions are determined from the complicated C 4 F 8 reaction set used in the model. The C 4 F 8 plasma fragmentation is explained, taking into account many factors, such as the EEPF characteristics, the dominance of primary and secondary processes, and the thresholds of dissociation and ionization. The simulation results are compared with experiments from literature, and reasonable agreement is obtained. Some discrepancies are observed, which can probably be attributed to the simplified polymer surface kinetics assumed in the model.

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“…Such processes have not yet been included in the models for C 4 F 8 reported up to now. [25][26][27]32,37…”

Section: Validation and Limitations Of The Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Bulk plasma fragmentation in a C4F8 inductively coupled plasma: A hybrid modeling study

Zhao

Zhang

Gao

et al. 2015

Journal of Applied Physics

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“…5,6 Radicals in the plasmas are formed through dissociation of neutral species by electron impact or dissociative electron attachment, or by surface reactions. 5,[7][8][9] Radical loss processes are self-reaction, further dissociation through electron impact, surface reaction, or through electron attachment. 7,9,10 The latter is particularly intriguing because it replaces a concentration of radicals, which may directly etch a surface by reacting to form a volatile species, with anions, which are unlikely to interact with a surface due to the electronegative sheath surrounding the plasma.…”

Section: Introductionmentioning

confidence: 99%

“…5,[7][8][9] Radical loss processes are self-reaction, further dissociation through electron impact, surface reaction, or through electron attachment. 7,9,10 The latter is particularly intriguing because it replaces a concentration of radicals, which may directly etch a surface by reacting to form a volatile species, with anions, which are unlikely to interact with a surface due to the electronegative sheath surrounding the plasma. Several studies have investigated electron attachment to fluorocarbon radicals either theoretically [11][12][13] or experimentally.…”

Section: Introductionmentioning

confidence: 99%

Electron attachment to C2 fluorocarbon radicals at high temperature

Shuman

Miller

Viggiano

2013

The Journal of Chemical Physics

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Thermal electron attachment to the radical species C2F3 and C2F5 has been studied over the temperature range 300-890 K using the Variable Electron and Neutral Density Attachment Mass Spectrometry technique. Both radicals exclusively undergo dissociative attachment to yield F(-). The rate constant for C2F5 shows little dependence over the temperature range, remaining ~4 × 10(-9) cm(3) s(-1). The rate constant for C2F3 attachment rises steeply with temperature from 3 × 10(-11) cm(3) s(-1) at 300 K to 1 × 10(-9) cm(3) s(-1) at 890 K. The behaviors of both species at high temperature are in agreement with extrapolations previously made from data below 600 K using a recently developed kinetic modeling approach. Measurements were also made on C2F3Br and C2F5Br (used in this work as precursors to the radicals) over the same temperature range, and, for C2F5Br as a function of electron temperature. The attachment rate constants to both species rise with temperature following Arrhenius behavior. The attachment rate constant to C2F5Br falls with increasing electron temperature, in agreement with the kinetic modeling. The current data fall in line with past predictions of the kinetic modeling approach, again showing the utility of this simplified approach.

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“…In the dry etching community, CF 4 has attracted much theoretical [22][23][24][25] and experimental [26][27][28][29] research interest for etching SiO 2 and plasma chamber cleaning processes [30][31][32]. Its relatively inert nature in its electronic ground state and the property of generating no stable excited states make it ideal for producing the desired neutral and ionic species in a controlled manner.…”

Section: Introductionmentioning

confidence: 99%

Mass spectrometric study of discharges produced by a large-area dual-frequency–dual-antenna inductively coupled plasma source

Mishra¹,

Kim²,

Kim³

et al. 2012

J. Phys. D: Appl. Phys.

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An energy-resolved quadrupole mass spectrometer is used to investigate the time-averaged ion energy distribution (IED) of positive ionic species in an Ar/CF 4 (90%/10%) discharge produced by dual-frequency-dual-antenna, next-generation large-area inductively coupled plasma source. The operating pressure is 10 mTorr. Two radio frequencies of 2 MHz (low frequency) and 13.56 MHz (high frequency) are used to initiate and sustain the discharge. The orifice of the mass spectrometer was 100 µm in diameter and placed at 30 mm below the ICP source and 20 mm outside the discharge volume.It is observed that both of the frequencies have significant effect on IEDs of all prominent discharge species. The evolution of IEDs with power shows that the discharge undergoes a mode transition (E to H) as the applied power is increased. At a fixed value of P 13.56 MHz (250 and 500 W), the energy spread and the energy separation between two peaks of IEDs increase illustrating enhanced E-mode. Above P 13.56 MHz = 500 W, the IEDs show opposite trends, i.e. decreasing energy spread and energy separation between two peaks, showing the strengthening of H-mode. Increasing P 13.56 MHz at a fixed value of P 2 MHz has similar effects. A comparison of IEDs sampled at a fixed total power (P 13.56 MHz + P 2 MHz ) demonstrates that an IED can be tailored by changing the power ratio (P 13.56 MHz/P 2 MHz).

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Mechanisms for CF2 radical generation and loss on surfaces in fluorocarbon plasmas

Abstract: Articles you may be interested inSurface loss rates of H and Cl radicals in an inductively coupled plasma etcher derived from time-resolved electron density and optical emission measurements

Cited by 65 publications

References 26 publications

Bulk plasma fragmentation in a C4F8 inductively coupled plasma: A hybrid modeling study

Bulk plasma fragmentation in a C4F8 inductively coupled plasma: A hybrid modeling study

Electron attachment to C2 fluorocarbon radicals at high temperature

Mass spectrometric study of discharges produced by a large-area dual-frequency–dual-antenna inductively coupled plasma source

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