Real-time monitoring of charge accumulation during pulse-time-modulated plasma

Ohtake, Hiroto; Jinnai, Butsurin; Suzuki, Yuya; Soda, Shinnosuke; Shimmura, Tadashi; Samukawa, Seiji

doi:10.1116/1.2362724

Cited by 12 publications

(7 citation statements)

References 15 publications

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“…We note that there are several other strategies to control charging of features that rely on pulsed plasmas. 22,23 In this approach, the source power is pulsed producing an active glow discharge, followed by an afterglow in which electrons rapidly attach to form a positive ion-negative ion plasma. Application of a bias during the afterglow then accelerates negative ions into the feature to neutralize excess positive charge.…”

Section: Charging Of Featuresmentioning

confidence: 99%

“…Pulsed power excitation can address many of the detriments of charging by elevating the ion energy, 20 reducing the thickness of fluorocarbon films on sidewalls, 21 and enabling the injection of negative ions to neutralize positive charge inside the feature. 22,23 Optimizing plasma etching of HAR features requires precise control of both the fluxes of ions and neutrals. In fluorocarbon plasmas, fluxes of CF x neutrals are produced by electron impact dissociation followed by diffusion to the wafer.…”

Section: Introductionmentioning

confidence: 99%

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Plasma etching of high aspect ratio features in SiO2 using Ar/C4F8/O2 mixtures: A computational investigation

Huang

Huard

Shim

et al. 2019

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Plasma etching of high aspect ratio (HAR) features, typically vias, is a critical step in the fabrication of high capacity memory. With aspect ratios (ARs) exceeding 50 (and approaching 100), maintaining critical dimensions (CDs) while eliminating or diminishing twisting, contact-edge-roughening, and aspect ratio dependent etching (ARDE) becomes challenging. Integrated reactor and feature scale modeling was used to investigate the etching of HAR features in SiO 2 with ARs up to 80 using tri-frequency capacitively coupled plasmas sustained in Ar/C 4 F 8 /O 2 mixtures. In these systems, the fluxes of neutral radicals to the wafer exceed the fluxes of ions by 1-2 orders of magnitude due to lower threshold energies for dissociation compared with ionization. At low ARs (<5), these abundant fluxes of CF x and C x F y radicals to the etch front passivate the oxide to form a complex which is then removed by energetic species (ions and hot neutrals) through chemically enhanced reactive etching, resulting in the formation of gas phase SiF x , CO x , and COF. As the etching proceeds into higher ARs, the fractional contribution of physical sputtering to oxide removal increases as the fluxes of energetic species to the etch front surpass those of the conduction constrained CF x and C x F y radicals. The instantaneous etch rate of oxide decreases with increasing aspect ratio (ARDE effect) due to decreased fluxes of energetic species and decreased power delivered by these species to the etch front. As the etch rate of photoresist (PR) is independent of AR, maintaining CDs by avoiding undercut and bowing requires high SiO 2-over-PR selectivity, which in turn requires a minimum thickness of the PR at the end of etching. Positive ions with narrow angular distributions typically deposit charge on the bottom of low AR features, producing a maximum in positive electric potential on the bottom of the feature. For high AR features, grazing incidence collisions of ions on sidewalls depositing charge produce electric potentials with maxima on the sidewalls (as opposed to the bottom) of the feature.

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Section: Charging Of Featuresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Plasma etching of high aspect ratio features in SiO2 using Ar/C4F8/O2 mixtures: A computational investigation

Huang

Huard

Shim

et al. 2019

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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“…12,13) Previous studies have focused on the effect of charge build-up at the bottom part of the hole to explain this phenomenon. [14][15][16][17][18][19] We assume that in addition to this charge build-up effect, other factors, such as mask deformation, are also important because the ion energy in HARC etching process is extremely high. In these previous reports, there are no discussions regarding mask effect, and the key parameter causing profile degradation is not well understood.…”

Section: Introductionmentioning

confidence: 99%

Effects of Mask and Necking Deformation on Bowing and Twisting in High-Aspect-Ratio Contact Hole Etching

Miyake

Negishi

Izawa

et al. 2009

Jpn. J. Appl. Phys.

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The effects of mask characteristics on high-aspect-ratio contact hole (HARC) etching profiles were investigated. The evaluation of etching profiles produced with different taper angle masks confirmed that the bowing amount and mask selectivity worsened with decreasing mask taper angle. The relationship between mask taper angle and distribution of scattered ion flux on the sidewall of a tapered mask was calculated. The scattered ion flux was heavily concentrated in the upper part of the sidewall in the case of a tapered mask, and this was considered to be the main cause of the bowing formation. Direct observation of an etched sidewall by atomic force microscopy (AFM) revealed that the roughness of the necking was strongly related to the roughness of the bottom part of the etched sidewall. To evaluate the dependence of twisting on nonuniform necking, the incident ion flux in a circular hole was calculated. As a result, in the case of nonaxisymmetric necking, an imbalance of ion flux in the bottom of the hole appeared and broke the etching symmetry in the bottom part of the hole, causing twisting. In addition, the probability of twisting was found to increase with increasing necking growth rate irrespective of mask electrification. Therefore, mask deformation and nonuniform necking in the upper part of the sidewall during HARC etching are considered the main factors causing bottom degradation. Accordingly, a vertical and nondeformed mask is very important for a smaller critical dimension (CD) and HARC etching.

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“…24,26) On the contrary, pulsed plasma with pulsing source power has also been studied extensively. [27][28][29][30][31][32][33] Pulsed plasma provides variable electron temperature and plasma density by pulsing. It controls dissociation and supplies highly selective etch.…”

Section: Introductionmentioning

confidence: 99%

Highly selective Si₃N₄ etching on Si using pulsed-microwave CH₃F/O₂/Ar plasma

Morimoto

Matsui

Ikeda

et al. 2023

Jpn. J. Appl. Phys.

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Highly selective Si3N4 etching on Si was achieved in a CH3F/O2/Ar plasma using pulsed-microwave plasma and time-modulation (TM) bias. The Si3N4/Si selectivity reached infinity at a peak-to-peak voltage (Vpp) of 240 V. The effect of pulsed-microwave on CH3F gas dissociation for highly selective Si3N4 etching was investigated by deposited film analysis, optical emission spectroscopy (OES), and ion current flux measurements. As the duty cycle of the pulsed-microwave was decreased, the plasma density during the pulse on period decreased and the CH/H ratio increased. The pulsed-microwave plasma produced low-dissociation radicals by providing a low plasma density. The low-dissociation radicals in the CH3F plasma formed a fluorine (F)-rich hydrofluorocarbon (HFC) layer on the Si3N4 wafer surface. The F-rich HFC layer promotes Si3N4 etching even at low ion energy, where Si etching does not proceed, and enables highly selective Si3N4 etching on Si.

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Real-time monitoring of charge accumulation during pulse-time-modulated plasma

Cited by 12 publications

References 15 publications

Plasma etching of high aspect ratio features in SiO2 using Ar/C4F8/O2 mixtures: A computational investigation

Plasma etching of high aspect ratio features in SiO2 using Ar/C4F8/O2 mixtures: A computational investigation

Effects of Mask and Necking Deformation on Bowing and Twisting in High-Aspect-Ratio Contact Hole Etching

Highly selective Si₃N₄ etching on Si using pulsed-microwave CH₃F/O₂/Ar plasma

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Real-time monitoring of charge accumulation during pulse-time-modulated plasma

Cited by 12 publications

References 15 publications

Plasma etching of high aspect ratio features in SiO2 using Ar/C4F8/O2 mixtures: A computational investigation

Plasma etching of high aspect ratio features in SiO2 using Ar/C4F8/O2 mixtures: A computational investigation

Effects of Mask and Necking Deformation on Bowing and Twisting in High-Aspect-Ratio Contact Hole Etching

Highly selective Si3N4 etching on Si using pulsed-microwave CH3F/O2/Ar plasma

Contact Info

Product

Resources

About

Highly selective Si₃N₄ etching on Si using pulsed-microwave CH₃F/O₂/Ar plasma