A Highly Selective Photoresist Ashing Process for Silicon Nitride Films   by Addition of Trifluoromethane

Saitô, Makoto; Etô, Hideo; Makino, Nobuaki; Omiya, Kayoko; Homma, Tetsuya; Nagatomo, Takao

doi:10.1143/jjap.40.5271

Cited by 18 publications

(12 citation statements)

References 11 publications

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“…Several studies have reported the formation of an AFS layer on SiN films using HFC and NH 3 /NF 3 -related plasmas. ,, 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. , In our study, we demonstrate a similar behavior by a different approach without the use of thermal irradiation. Figure illustrates an overview of the presented ALE and etching mechanism, based on the in situ FTIR and EPC results.…”

Section: Resultssupporting

confidence: 74%

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: Resultssupporting

confidence: 74%

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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“…As the H 2 concentration increased to 27%, the contribution of the N–H x component noticeably increased. A small component corresponding to the NH 4 + bond at binding energy around 402 eV, , indicative of the presence of the ammonia fluorosilicate (AFS), (NH 4 ) 2 SiF 6 phase, can also be observed. This observation is consistent with previous studies that used other hydrogen-contained fluorocarbon plasmas. , Furthermore, a peak at the low energy side, corresponding to the N–Si 3 bond (∼398 eV), is also observed.…”

Section: Resultsmentioning

confidence: 99%

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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“…It was previously determined that ammonium hexafluorosilicate forms on the surface of Si3N4 film after exposure to CF4 plasma when the film surface is hydrogenated and oxygenated 18 . Subsequently, the detection of ammonium salt on Si3N4 after plasma was reported for various plasmas such as NF3/O2/NH3 19 , CF4/H2/O2 20 , and CHF3/O2 21 . An XPS study also reported that ammonium hexafluorosilicate formed on a plasma-exposed Si3N4 is eliminated after heating at 300 °C21 .…”

Section: Si3n4 and Tin Ale Selective To Sio2 And Poly-simentioning

confidence: 99%

Selective isotropic atomic-layer etching of thin films by using dry chemical removal tool

Shinoda

Miyoshi

Kobayashi

et al. 2023

Advanced Etch Technology and Process Integration for Nanopatterning XII

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There has been considerable interest in the development of isotropic atomic layer etching (ALE) for the conformal removal of thin films. Material selectivity is crucial for the development of isotropic ALE because the next generation of semiconductor devices will be constructed with miniaturized 3D structures using a variety of very thin films. We developed plasma-assisted thermal-cyclic ALE, which is a repetition of surface modification by plasma exposure and removal of the modified surface by infrared heating. We developed a 300-mm tool, namely, dry chemical removal (DCR), which is equipped with an inductively coupled plasma (ICP) source and infrared lamps, to facilitate rapid thermal desorption of the modified surface. An important feature of the plasma-assisted thermal-cyclic ALE is that it has more tuning knobs than that of conventional ALE because it uses two temperatures: a low temperature for surface modification and an elevated temperature for the removal of the modified surface. This paper presents the selective ALE of various materials, i.e., Si3N4, TiN, W, and SiGe using the developed tool. The mechanisms of the selectivity are divided into two categories: formation of an ammonium salt-based modified layer and selectivity control by adjusting the infrared heating time. This paper reviews the selective ALE mechanisms, focusing on the results of in situ analysis of surface reactions, and presents some of the latest findings.

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A Highly Selective Photoresist Ashing Process for Silicon Nitride Films by Addition of Trifluoromethane

Cited by 18 publications

References 11 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

Selective isotropic atomic-layer etching of thin films by using dry chemical removal tool

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A Highly Selective Photoresist Ashing Process for Silicon Nitride Films by Addition of Trifluoromethane

Cited by 18 publications

References 11 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

Selective isotropic atomic-layer etching of thin films by using dry chemical removal tool

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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