Etching Mechanisms and Surface Conditions for SiOxNy Thin Films in CF4 + CHF3 + O2 Inductively Coupled Plasma

Lee, Junmyung; Kim, Jihun; Efremov, Alexander; Kim, Changmok; Lee, Hyun Woo; Kwon, Kwang‐Ho

doi:10.1007/s11090-019-09973-w

Cited by 8 publications

(16 citation statements)

References 49 publications

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“…The latter were represented either by one fluorocarbon component (CF 4 , C 4 F 8 , CHF 3 ) with Ar and O 2 or by two fluorocarbon components with one additive gas. In contrast to “classical” works [ 39 , 41 , 75 , 76 ], we did not use surface diagnostics methods, did not measure the polymer film thickness and did not investigate its chemical structure. Instead, we performed a phenomenological study based on correlations between experimentally obtained etching kinetics and model-predicted gas-phase plasma characteristics (ion energy, ion flux, densities and fluxes of F atoms and polymerizing radicals) providing various heterogeneous effects.…”

Section: Discussionmentioning

confidence: 99%

On Relationships between Gas-Phase Chemistry and Reactive Ion Etching Kinetics for Silicon-Based Thin Films (SiC, SiO2 and SixNy) in Multi-Component Fluorocarbon Gas Mixtures

2021

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This work summarizes the results of our previous studies related to investigations of reactive ion etching kinetics and mechanisms for widely used silicon-based materials (SiC, SiO2, and SixNy) as well as for the silicon itself in multi-component fluorocarbon gas mixtures. The main subjects were the three-component systems composed either by one fluorocarbon component (СF4, C4F8, CHF3) with Ar and O2 or by two fluorocarbon components with one additive gas. The investigation scheme included plasma diagnostics by Langmuir probes and model-based analysis of plasma chemistry and heterogeneous reaction kinetics. The combination of these methods allowed one (a) to figure out key processes which determine the steady-state plasma parameters and densities of active species; (b) to understand relationships between processing conditions and basic heterogeneous process kinetics; (c) to analyze etching mechanisms in terms of process-condition-dependent effective reaction probability and etching yield; and (d) to suggest the set gas-phase-related parameters (fluxes and flux-to-flux ratios) to control the thickness of the fluorocarbon polymer film and the change in the etching/polymerization balance. It was shown that non-monotonic etching rates as functions of gas mixing ratios may result from monotonic but opposite changes in F atoms flux and effective reaction probability. The latter depends either on the fluorocarbon film thickness (in high-polymerizing and oxygen-less gas systems) or on heterogeneous processes with a participation of O atoms (in oxygen-containing plasmas). It was suggested that an increase in O2 fraction in a feed gas may suppress the effective reaction probability through decreasing amounts of free adsorption sites and oxidation of surface atoms.

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Section: Discussionmentioning

confidence: 99%

On Relationships between Gas-Phase Chemistry and Reactive Ion Etching Kinetics for Silicon-Based Thin Films (SiC, SiO2 and SixNy) in Multi-Component Fluorocarbon Gas Mixtures

2021

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“…The basic features of reactive‐ion etching processes in fluorocarbon‐based plasmas as well as related reaction mechanisms for Si, SiO 2 , and Si 3 N 4 have been discussed in detail in References [5,8–10,14,18,19,42–44]. When summarizing these findings, the following general approaches for the analysis of etching kinetics may be used: Under the reactive‐ion etching conditions (i.e., when the ion bombardment energy exceeds the sputtering threshold for the target surface), the measured etching rate,

R

, may be represented in a form of two summands,

R_{phys} + R_{chem}

.…”

Section: Experimental and Modeling Detailsmentioning

confidence: 99%

“…When summarizing these findings, the following general approaches for the analysis of etching kinetics may be used: Under the reactive‐ion etching conditions (i.e., when the ion bombardment energy exceeds the sputtering threshold for the target surface), the measured etching rate,

R

, may be represented in a form of two summands,

R_{phys} + R_{chem}

. [ 5,42–44 ] These represent physical (sputtering by ion bombardment) and chemical (ion‐assisted chemical reaction) etching pathways, respectively. The ion‐assisted chemical reaction has the rate of

γ_{R} Γ_{F}

, [ 18,19,43 ] where

γ_{R}

is the effective reaction probability, which accounts for the net effect from all surface‐related stages, and

Γ_{F} \approx n_{F} υ_{T} / 4

is the fluorine atom flux. In general case, the effective reaction probability

γ_{R} \approx s_{0} false(1 - θ false)

[ 19 ] depends on surface temperature (through the sticking coefficient

s_{0}

) as well as on any factor influencing the fraction of free adsorption sites for F atoms

false(1 - θ false)

.…”

Section: Experimental and Modeling Detailsmentioning

confidence: 99%

“…In polymerizing plasmas,

γ_{R}

decreases with increasing thickness of the fluorocarbon polymer film when the latter is enough to provide

{normalΓ}_{normalF}^{'} / Γ_{F}

<< 1, where

{normalΓ}_{normalF}^{'}

is the flux of F atoms on the polymer film/etched surface interface. [ 5,10,14,19 ] The physical sputtering (as well as any other ion‐related etching effect with a purely physical nature: Breaking of chemical bonds between surface atoms, ion‐stimulated desorption of reaction products) has the rate of

Y_{S} Γ_{+}

, [ 5,44 ] where

Y_{S}

∼

\sqrt{M_{i} ε_{i}}

[ 18,43 ] is the sputtering yield,

M_{i} = m_{i} N_{A}

is the effective ion molar mass,

ε_{i} = | - U_{f} - U_{dc} |

is the ion bombardment energy,

{- U}_{f} \approx 0.5 T_{e} normalln false(m_{i} / {2 π m}_{e} false)

is the floating potential, and

Γ_{+} \approx J_{+} / e

is the flux of positive ions. Accordingly, the relative change in the corresponding process rate may be traced by the parameter

\sqrt{M_{i} ε_{i}} Γ_{+}

.…”

Section: Experimental and Modeling Detailsmentioning

confidence: 99%

“…Accordingly, the relative change in the corresponding process rate may be traced by the parameter

\sqrt{M_{i} ε_{i}} Γ_{+}

. [ 18,43 ] The growth of the fluorocarbon polymer film is provided by the CF x ( x = 1, 2) radicals, and the polymerization ability increases in fluorine‐poor plasmas. [ 8,10 ] Accordingly, the polymer deposition rate may be traced by the

Γ_{pol} / Γ_{F}

ratio, [ 19,31,32 ] where

Γ_{pol} = Γ_{{CF}_{2}} + Γ_{CF}

, whereas parameters

Γ_{pol} / \sqrt{M_{i} ε_{i}} Γ_{+} Γ_{F}

and

Γ_{pol} / Γ_{O} Γ_{F}

characterize the change in the polymer film thickness due to physical (destruction by ion bombardment) and chemical (etching by O atoms) destruction pathways, respectively.…”

Section: Experimental and Modeling Detailsmentioning

confidence: 99%

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Gas‐phase chemistry and reactive‐ion etching kinetics for silicon‐based materials in C₄F₈ + O₂ + Ar plasma

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2021

Plasma Processes & Polymers

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In this study, we investigated the effects of C4F8/O2 and Ar/O2 component ratios in C4F8 + O2 + Ar gas system on plasma parameters, gas‐phase chemistry, and etching kinetics for Si, SiO2, and Si3N4 under the condition of inductively coupled radiofrequency (13.56 MHz) plasma. The use of plasma diagnostics by Langmuir probes, together with the zero‐dimensional plasma modeling, allowed one to compare two different gas mixing regimes in respect to (a) electrons‐ and ions‐related plasma parameters; (b) steady‐state densities of plasma active species; and (c) formation and decay kinetics for F atoms and polymerizing radicals. It was shown that variations in both C4F8/O2 and Ar/O2 mixing ratios result in nonmonotonic (with maximums at ∼10% to 15% O2) Si, SiO2, and Si3N4 etching rates as well as in opposite changes in corresponding effective reaction probabilities. The model‐based analysis of etching mechanisms allowed one to suggest that the net effect from all heterogeneous (i.e., appeared on the etched surface) interaction pathways may be controlled either by the fluorocarbon radical flux (in the case of Ar/O2 mixing ratios at constant fraction of C4F8) through the polymer film thickness or by the O atom flux (in the case of C4F8/O2 mixing ratios at constant fraction of Ar) through the balance of adsorption sites.

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Organofluorine Chemical Gases of Industrial Importance in Semiconductor Materials Processing

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Organofluorine chemical (OFC) gases are important products of the fluorochemicals industry and find major usage as essential materials that largely impact semiconductor materials processing in the creation of computer chip technologies. These OFC gases provide highly reactive sources of fluorine and fluorocarbon radical species and thus form the foundation upon which plasma‐based etching and chamber cleaning processes are built. An important aspect of OFC gases is their fluorine to carbon (F:C) ratio, a parameter that reflects their reactivity in plasma‐based processes of importance for integrated circuit (IC) fabrication technology. OFC gases used in the semiconductor materials‐processing area are prepared on an industrial scale through a variety of synthetic processes. These processes include direct and indirect addition of elemental fluorine (F 2 ), fluorine substitution, halogen exchange, hydrogen addition/dehydrofluorination, pyrolysis, and building‐block methodologies.

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Etching Mechanisms and Surface Conditions for SiOxNy Thin Films in CF4 + CHF3 + O2 Inductively Coupled Plasma

Cited by 8 publications

References 49 publications

On Relationships between Gas-Phase Chemistry and Reactive Ion Etching Kinetics for Silicon-Based Thin Films (SiC, SiO2 and SixNy) in Multi-Component Fluorocarbon Gas Mixtures

On Relationships between Gas-Phase Chemistry and Reactive Ion Etching Kinetics for Silicon-Based Thin Films (SiC, SiO2 and SixNy) in Multi-Component Fluorocarbon Gas Mixtures

Gas‐phase chemistry and reactive‐ion etching kinetics for silicon‐based materials in C₄F₈ + O₂ + Ar plasma

Organofluorine Chemical Gases of Industrial Importance in Semiconductor Materials Processing

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Etching Mechanisms and Surface Conditions for SiOxNy Thin Films in CF4 + CHF3 + O2 Inductively Coupled Plasma

Cited by 8 publications

References 49 publications

On Relationships between Gas-Phase Chemistry and Reactive Ion Etching Kinetics for Silicon-Based Thin Films (SiC, SiO2 and SixNy) in Multi-Component Fluorocarbon Gas Mixtures

On Relationships between Gas-Phase Chemistry and Reactive Ion Etching Kinetics for Silicon-Based Thin Films (SiC, SiO2 and SixNy) in Multi-Component Fluorocarbon Gas Mixtures

Gas‐phase chemistry and reactive‐ion etching kinetics for silicon‐based materials in C4F8 + O2 + Ar plasma

Organofluorine Chemical Gases of Industrial Importance in Semiconductor Materials Processing

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Product

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Gas‐phase chemistry and reactive‐ion etching kinetics for silicon‐based materials in C₄F₈ + O₂ + Ar plasma