Manipulation of etch selectivity of silicon nitride over silicon dioxide to a-carbon by controlling substate temperature with a CF4/H2 plasma

Hsiao, S.N.; Britun, Nikolay; Nguyen, Thi‐Thuy‐Nga; Tsutsumi, Takayoshi; Ishikawa, Kenji; Sekine, Makoto; Hori, Masaru

doi:10.1016/j.vacuum.2023.111863

Cited by 10 publications

(11 citation statements)

References 49 publications

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“…To assess the properties of the films, many material characterization techniques were used. The details regarding the properties of the films can be found in our previous studies. , The thickness of the films with pristine state was measured with an X-ray reflectivity (XRR) technique. The thickness variation in the etching step was analyzed in real-time mode with the SE system (M-2000, J.A.…”

Section: Methodsmentioning

confidence: 99%

“…Several studies have reported the formation of an AFS layer on SiN films using HFC and NH 3 /NF 3 -related plasmas. 34,51,52 Miyoshi et al used the formation of AFS through CH 2 F 2 /O 2 or CHF 3 /O 2 plasmas in the ALE process, combined with IR annealing to facilitate the sublimation of AFS. 30,53 In our study, we demonstrate a similar behavior by a different approach without the use of This process occurs when both the HFC and AFS thicknesses are sufficiently thin.…”

Section: Etching Mechanism Of Sin Alementioning

confidence: 99%

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In Situ Monitoring of Etching Characteristic and Surface Reactions in Atomic Layer Etching of SiN Using Cyclic CF₄/H₂ and H₂ Plasmas

Hsiao

Sekine

Hori

2023

ACS Appl. Mater. Interfaces

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Cyclic atomic layer etching (ALE) of SiN with high selectivity to SiO2, utilizing a hydrofluorocarbon deposition followed by exposure to hydrogen plasma, is presented. The surface reaction mechanism and etching behavior were investigated with in situ attenuated total reflectance Fourier transformation infrared spectroscopy (ATR-FTIR) and spectroscopic ellipsometry. In the deposition step, the hydrofluorocarbon film was deposited on top of the SiN films using the CF4/H2 plasmas with varying H2 contents (33 to 85%). Subsequently, the surface-modified SiN film was exposed to a hydrogen plasma for etching. The self-limiting SiN etching was observed, where the etch depth solely depended on the F concentration of the deposited hydrofluorocarbon layer once its thickness exceeded a critical value. A high selectivity of approximately 8.6 for SiN over SiO2 was achieved. The in situ ATR-FTIR spectra revealed that during the deposition step, besides the formation of the C–H peak associated with hydrofluorocarbon deposition, the appearance of the N–H4 absorbance band indicated the formation of an ammonium fluorosilicate layer on top of SiN. In the subsequent H2 plasma etching step, both the surface modification layer and the pre-deposited hydrofluorocarbon layer were removed. The removal of the surface-modified layer and hydrofluorocarbon layer was associated with the etch rate during H2 plasma exposure. These findings indicate the importance of the formation and removal of the surface modification layer for achieving ALE of SiN. The dissociation of the hydrofluorocarbon layer by the H2 plasma released reactants that interacted with SiN, leading to the formation of a new surface modification layer. The etching process significantly slowed down once the hydrofluorocarbon deposition and surface modification layer were completely removed.

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Section: Methodsmentioning

confidence: 99%

Section: Etching Mechanism Of Sin Alementioning

confidence: 99%

In Situ Monitoring of Etching Characteristic and Surface Reactions in Atomic Layer Etching of SiN Using Cyclic CF₄/H₂ and H₂ Plasmas

Hsiao

Sekine

Hori

2023

ACS Appl. Mater. Interfaces

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“…, AFS, owing to its lower heat of formation (AFS: −2681 kJ/mol; SiF 4 : −1615 kJ/mol; and NH 3 : −80 kJ/mol) . Therefore, the etching process is determined by the dissociation of AFS to volatile SiF 4 and NH 3 through high-energy ion bombardment when the substrate is maintained at room temperature, as AFS is more unstable at high temperature. ,, Our data demonstrate that the substantial decrease in F due to H 2 addition did not lead to a corresponding decrease in ER. This suggests the hypothesis that HF may spontaneously react with the hydrogenated SiN surface to form the AFS phase, resembling the hydrous HF etching mechanism via hydrogen bonding interactions .…”

Section: Etching Model and Discussionmentioning

confidence: 67%

“…8,52,53 Due to the reactions between hydrogen-contained fluorocarbon plasma and SiN, these processes enable selective etching of SiN over SiO 2 and other Si-based materials. 10,[12][13][14]54 In these plasmas, the H atoms scavenge the F atoms, forming HF molecules, resulting in fluorine poor conditions and high polymer deposition rates. This phenomenon is particularly significant for Si and SiO 2 etching, as they are generally considered to have no reaction with gaseous HF.…”

Section: ■ Etching Model and Discussionmentioning

confidence: 99%

“…10−13 Additionally, the dependence of selectivities between Si-based materials on substrate temperature has recently been investigated by various research groups. 14,15 In hydrogen-contained fluorocarbon plasmas, the formation of hydrogen fluoride (HF) is anticipated to have a detrimental effect on etching for Si-based materials, as it tends to scavenge F radicals. 16 In the mechanism of SiN etching, the H also reacts with N and CF x species, resulting in the formation of HCN as a byproduct, which helps to reduce the FC polymerization and facilitates the progress of SiN etching.…”

Section: ■ Introductionmentioning

confidence: 99%

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Etching Mechanism Based on Hydrogen Fluoride Interactions with Hydrogenated SiN Films Using HF/H₂ and CF₄/H₂ Plasmas

Hsiao,

Britun,

Nguyen

et al. 2023

ACS Appl. Electron. Mater.

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Pseudo‐Wet Plasma Mechanism Enabling High‐Throughput Dry Etching of SiO₂ by Cryogenic‐Assisted Surface Reactions

Hsiao,

Sekine,

Britun

et al. 2024

Small Methods

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Manufacturing semiconductor devices requires advanced patterning technologies, including reactive ion etching (RIE) based on the synergistic interactions between ions and etch gas. However, these interactions weaken as devices continuously scale down to sub‐nanoscale, primarily attributed to the diminished transport of radicals and ions into the small features. This leads to a significant decrease in etch rate (ER). Here, a novel synergistic interaction involving ions, surface‐adsorbed chemistries, and materials at cryogenic temperatures is found to exhibit a significant increase in the ER of SiO2 using CF4/H2 plasmas. The ER increases twofold when plasma with H2/(CF4 + H2) = 33% is used and the substrate temperature is lowered from 20 to −60 °C. The adsorption of HF and H2O on the SiO2 surface at cryogenic temperatures is confirmed using in situ Fourier transform infrared spectroscopy. The synergistic interactions of the surface‐adsorbed HF/H2O as etching catalysts and plasma species result in the ER enhancement. Therefore, a mechanism called “pseudo‐wet plasma etching” is proposed to explain the cryogenic etching process. This synergy demonstrates that the enhanced etch process is determined by the surface interactions between ions, surface‐adsorbed chemistry, and the material being etched, rather than interactions between ion and gas phase, as observed in the conventional RIE.

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Manipulation of etch selectivity of silicon nitride over silicon dioxide to a-carbon by controlling substate temperature with a CF4/H2 plasma

Cited by 10 publications

References 49 publications

In Situ Monitoring of Etching Characteristic and Surface Reactions in Atomic Layer Etching of SiN Using Cyclic CF₄/H₂ and H₂ Plasmas

In Situ Monitoring of Etching Characteristic and Surface Reactions in Atomic Layer Etching of SiN Using Cyclic CF₄/H₂ and H₂ Plasmas

Etching Mechanism Based on Hydrogen Fluoride Interactions with Hydrogenated SiN Films Using HF/H₂ and CF₄/H₂ Plasmas

Pseudo‐Wet Plasma Mechanism Enabling High‐Throughput Dry Etching of SiO₂ by Cryogenic‐Assisted Surface Reactions

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Manipulation of etch selectivity of silicon nitride over silicon dioxide to a-carbon by controlling substate temperature with a CF4/H2 plasma

Cited by 10 publications

References 49 publications

In Situ Monitoring of Etching Characteristic and Surface Reactions in Atomic Layer Etching of SiN Using Cyclic CF4/H2 and H2 Plasmas

In Situ Monitoring of Etching Characteristic and Surface Reactions in Atomic Layer Etching of SiN Using Cyclic CF4/H2 and H2 Plasmas

Etching Mechanism Based on Hydrogen Fluoride Interactions with Hydrogenated SiN Films Using HF/H2 and CF4/H2 Plasmas

Pseudo‐Wet Plasma Mechanism Enabling High‐Throughput Dry Etching of SiO2 by Cryogenic‐Assisted Surface Reactions

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Product

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In Situ Monitoring of Etching Characteristic and Surface Reactions in Atomic Layer Etching of SiN Using Cyclic CF₄/H₂ and H₂ Plasmas

In Situ Monitoring of Etching Characteristic and Surface Reactions in Atomic Layer Etching of SiN Using Cyclic CF₄/H₂ and H₂ Plasmas

Etching Mechanism Based on Hydrogen Fluoride Interactions with Hydrogenated SiN Films Using HF/H₂ and CF₄/H₂ Plasmas

Pseudo‐Wet Plasma Mechanism Enabling High‐Throughput Dry Etching of SiO₂ by Cryogenic‐Assisted Surface Reactions