Selective etching of SiN against SiO2 and poly-Si films in hydrofluoroethane chemistry with a mixture of CH2FCHF2, O2, and Ar

Hsiao, S.N.; Ishikawa, Kenji; Hayashi, Toshio; Ni, Jiwei; Tsutsumi, Takayoshi; Sekine, Makoto; Hori, Masaru

doi:10.1016/j.apsusc.2020.148439

Cited by 22 publications

(13 citation statements)

References 59 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In a conventional reactive ion etching, it has been reported that highly selective etch of SiN over SiO 2 can be achieved using hydrogen-contained plasmas, both with and without FC additives or HFCs. − Recently, Dussart et al also demonstrated the etch selectivities between SiN, SiO 2 , and Si materials by controlling bias voltage at cryogenic temperature regimes . Due to the scavenging reaction of H atoms with F, the concentration of F, which is considered as the main etchant for SiO 2 or Si, is expected to decrease with increasing H concentration.…”

Section: Resultsmentioning

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

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: Resultsmentioning

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

Self Cite

View full text Add to dashboard Cite

show abstract

“…Among them, replacing PFCs with lower GWP gases is considered the ultimate solution. − Studies have been reported on hydrofluorocarbons, unsaturated fluorocarbons, iodofluorocarbons, oxygen-containing fluorocarbons, fluoro-ethers, and fluoroalcohols to replace PFCs. − The GWP can be reduced by introducing iodine, hydrogen, or oxygen atoms in fluorocarbon molecules. − Iodine atoms have a weak bond with fluorocarbons and are easily decomposed in the atmosphere . Hydrofluorocarbons such as C 3 HF 5 , C 3 H 3 F 3 , CH 2 F 2 , and C 4 H 9 F reduce GWP because the hydrogen in these molecules induces the formation of non-global warming HF in plasma etching processes. − Fluorocarbon gases containing oxygen atoms in C 5 F 10 O, C 3 F 6 O, and c-C 4 F 8 O molecules are also being developed as potential alternatives to PFCs. − A small fraction of oxygen atoms in these molecules reduce GWPs and lifetimes by converting PFCs into CO, CO 2 , and COF 2 molecules while minimizing the side effects .…”

Section: Introductionmentioning

confidence: 99%

Low Global Warming C₄H₃F₇O Isomers for Plasma Etching of SiO₂and Si₃N₄Films

Kim

Kang

et al. 2022

ACS Sustainable Chem. Eng.

View full text Add to dashboard Cite

In this study, the plasmas of C4H3F7O fluoro-ether and fluoro-alcohol isomers of CF3CF2CF2OCH3 (HFE-347mcc3), (CF3)2CFOCH3 (HFE-347mmy), and CF3CF2CF2CH2OH (PPC) with low global warming potentials (GWPs) were characterized for etching SiO2, Si3N4, and poly-Si films. The C4H3F7O isomers have a short lifetime (<5 years) and low GWP (<1000) compared to the widely used C4F8, with a lifetime of 3200 years and a GWP100 of 10,592. Radicals in the plasma of C4H3F7O fluoro-ethers and fluoro-alcohol isomers were analyzed by mass spectroscopy, and HF and CO peaks were identified as major gas-phase products in the plasma phase. The concentration of exhaust gases after plasma etching were analyzed, and the million metric tons of carbon equivalent (MMTCE) were determined relative to conventional perfluorocarbon (PFC), C4F8. HF, CO, and COF2 were identified as the major reaction products in exhaust with C4H3F7O isomer plasmas. The MMTCEs of HFE-347mcc3, HFE-347mmy, and PPC were lowered by 82, 74, and 85%, respectively, compared with that of C4F8. The chemical bonding of the steady-state fluorocarbon film on SiO2, Si3N4, and poly-Si surfaces was analyzed during the etching process, and a lower F 1s/C 1s ratio was observed for C4H3F7O isomers than for C4F8. A high etch selectivity of 170 was achieved for SiO2 etching over poly-Si and 263 for Si3N4 etching over poly-Si with PPC plasma. This high selectivity is attributed to the higher carbon and lower fluorine contents in the steady-state fluorocarbon film. The C4H3F7O isomer plasmas also generate a superior etch profile compared to the C4F8 plasma with an aspect ratio of 7:1 etch of 200 nm hole patterns. This study demonstrates that C4H3F7O isomers can significantly reduce the global warming effect by replacing the conventional PFC in the etching processes of semiconductor device fabrication.

show abstract

“…Accordingly, the hydrofluoroethane compounds, which exhibit a favorable dissociation path to form CH 2 F + CHF 2 + or CH 2 F + + CHF 2 , have also been demonstrated to have suitable properties for etching SiN films through experiments and computational calculation. [ 16,17 ]…”

Section: Introductionmentioning

confidence: 99%

Effects of hydrogen content in films on the etching of LPCVD and PECVD SiN films using CF₄/H₂ plasma at different substrate temperatures

Hsiao

Britun

Nguyen

et al. 2021

Plasma Processes & Polymers

Self Cite

View full text Add to dashboard Cite

The dependences of etching characteristics on substrate temperature (Ts, from –20 to 50°C) of the plasma‐enhanced chemical vapor deposition (PECVD) SiN films (PE‐SiN) and low‐pressure chemical vapor deposition (LPCVD) SiN films (LP‐SiN) with CF4/H2 plasma were investigated. The Fourier‐transform infrared spectroscopy shows that both film types were N–H bond‐rich films, but in different hydrogen contents (PE‐SiN 22.7 at% and LP‐SiN 3.8 at%) from the Rutherford backscattering spectroscopy analyses. A higher hydrogen content led to a thinner fluorocarbon thickness because of the reaction between hydrogen outflux and C and N to form an HCN byproduct. The etch rates (ER) for the PE‐SiN were higher than that of the LP‐SiN at all Ts, due to the different FC thickness and etching mechanisms proposed. The formation of the N−Hx layer on PE‐SiN at low temperature caused the decrease in ER. For the LP‐SiN, the weak dependences of Ts on surface structure and ER were observed.

show abstract

Selective etching of SiN against SiO2 and poly-Si films in hydrofluoroethane chemistry with a mixture of CH2FCHF2, O2, and Ar

Cited by 22 publications

References 59 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

Low Global Warming C₄H₃F₇O Isomers for Plasma Etching of SiO₂and Si₃N₄Films

Effects of hydrogen content in films on the etching of LPCVD and PECVD SiN films using CF₄/H₂ plasma at different substrate temperatures

Contact Info

Product

Resources

About

Selective etching of SiN against SiO2 and poly-Si films in hydrofluoroethane chemistry with a mixture of CH2FCHF2, O2, and Ar

Cited by 22 publications

References 59 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

Low Global Warming C4H3F7O Isomers for Plasma Etching of SiO2and Si3N4Films

Effects of hydrogen content in films on the etching of LPCVD and PECVD SiN films using CF4/H2 plasma at different substrate temperatures

Contact Info

Product

Resources

About

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

Low Global Warming C₄H₃F₇O Isomers for Plasma Etching of SiO₂and Si₃N₄Films

Effects of hydrogen content in films on the etching of LPCVD and PECVD SiN films using CF₄/H₂ plasma at different substrate temperatures