On the Control of Plasma Parameters and Active Species Kinetics in CF4 + O2 + Ar Gas Mixture by CF4/O2 and O2/Ar Mixing Ratios

Sobolev

2020

IVKKT

The effect of Ar/O2 mixing ratio on gas-phase characteristics and SiO2 etching kinetics in CF4 + Ar + O2 and C4F8 + Ar + O2 plasmas was studied under conditions of 13.56 MHz inductive RF discharge. The constant processing parameters were fraction of fluorocarbon component in a feed gas (50%) total gas pressure (6 mTorr), input power (700 W) and bias power (200 W). It was found that the full substitution of Ar for O2 in both gas systems results in non-monotonic (with a maximum at ~ 25% Ar + 25% O2) SiO2 etching rates as well as in monotonically increasing photoresist etching rate with higher absolute values for CF4-containing mixture. The steady-state densities of active species were determined using a combination of plasma diagnostics by Langmuir probes and 0-dimensional (global) plasma modeling. Corresponding results indicated that both gas systems are characterized by quite close parameters of electron and ion components while exhibit sufficient differences in the kinetics of neutral species, especially in the presence of O2. The latter produces opposite changes in F atom density as well as in effective probability of ion-assisted chemical reaction vs. Ar/O2 mixing ratio. Relationships between type of fluorocarbon component and heterogeneous process kinetics were analyzed through the set of gas-phase-related parameters (fluxes, flux-to-flux ratios) characterizing chemical etching pathways for SiO2 and formation/destruction balance for the fluorocarbon polymer film. It was suggested that the transition toward O2-rich plasma in the low-polymerizing CF4 + Ar + O2 plasma suppresses the effective probability for SiO2 + F reaction through decreasing efficiency for oxide bond breaking and desorption of etching products due to decreasing ion energy flux. Oppositely, an increase in O2 content in the high-polymerizing C4F8 + Ar + O2 mixture lifts up the effective reaction probability by decreasing fluorocarbon film thickness and providing better access of F atoms to the etched surface.

Section: Experimental and Modeling Detailsmentioning

confidence: 99%

Section: Experimental and Modeling Detailsmentioning

confidence: 99%

“…Basic assumptions for the analysis of heterogeneous kinetics were also the same with those used in our previous works [15,16,[19][20][21]:…”

Section: Experimental and Modeling Detailsmentioning

confidence: 99%

Section: Experimental and Modeling Detailsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

FEATURES OF SiO2 REACTIVE-ION ETCHING KINETICS IN CF4 + Ar + O2 AND C4F8 + Ar + O2 GAS MIXTURES

Sobolev

2020

IVKKT

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

Lee

Plasma Processes & Polymers

Kwon

2021

Self Cite

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.

Comparative study of CF₄ + O₂ and C₆F₁₂O + O₂ plasmas for reactive‐ion etching applications

Lim

Plasma Processes & Polymers

Woo

et al. 2021

Self Cite

This work represents a comparative study of gas-phase parameters and reactive-ion etching kinetics for Si and Si and SiO 2 in CF 4 + O 2 and C 6 F 12 O + O 2 plasmas. An interest to the C 6 F 12 O gas is because it combines the low global warming potential (low environmental impact) and weakly studied dry etching performance. It was shown that the investigated gas systems showed similar effects of processing conditions on electron-and ion-related plasma parameters as well as on the densities of F and O atoms. Etching experiments showed identical behaviors of Si and SiO 2 etching rates as well as very similar SiO 2 /Si etching selectivities. The notable feature of the C 6 F 12 O + O 2 plasma is only the systematically lower absolute etching rates that correlate with lower in F atom densities.dodecafluorooxepane, global warming potential, heterogeneous reaction kinetics, ion energy and flux, plasma diagnostics, plasma modeling | INTRODUCTIONGases from the fluorocarbon family have an important place in the electronic device production industry, as they are used for dry (reactive-ion) patterning of Si and SiO 2 . [1][2][3] These two materials are widely used in planar integrated structures as either substrates (mostly silicon itself) or various functional layers (mostly silicon dioxide). [2][3][4][5] Recently, the increasing attention paid to both device dimensions and performance has led to the continuous optimization of dry etching techniques toward achieving more anisotropic etching profiles, lower surface damage and residues, and better SiO 2 /Si etching selectivities. Progress in this direction requires a thorough understanding of etching mechanisms, transparent interconnections between gas-phase plasma parameters and surface reaction kinetics, and known features of various fluorocarbon-based plasmas in respect to Si and SiO 2 etching processes.