Enhanced silicon nitride etching in the presence of F atoms: Quantum chemistry simulation

ACS Sustainable Chem. Eng.

Kang

et al. 2022

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.

Section: Resultsmentioning

confidence: 99%

Low Global Warming C₄H₃F₇O Isomers for Plasma Etching of SiO₂and Si₃N₄Films

ACS Sustainable Chem. Eng.

Kang

et al. 2022

ECS J. Solid State Sci. Technol.

“…For this purpose, yttrium oxide has been evaluated in a previous study. 15 The other widely used coating materials, such as tantalum carbide, 16 silicon nitride 17,18 and aluminum nitride, 19 should also be evaluated.…”

mentioning

confidence: 99%

Exposure of Tantalum Carbide, Silicon Nitride and Aluminum Nitride to Chlorine Trifluoride Gas

Haruguchi

Kawasaki

Habuka

et al. 2019

Widely used coating materials, such as tantalum carbide, silicon nitride and aluminum nitride, were exposed to chlorine trifluoride gas at various temperatures. The tantalum carbide powder was etched and vaporized by a quick and significant exothermic chemical reaction at temperatures higher than room temperature. The silicon nitride powder was etched that produced volatile products at temperatures higher than 250°C. An aluminum nitride plate and powder showed a slight increase in weight at temperatures higher than 500°C due to fluorination. The aluminum nitride plate thickness increased causing a surface smoothing effect without any cracking. The aluminum nitride is expected to work as the anticorrosive coating material to the chlorine fluoride gas at high temperatures, thus allowing fluorination.

“…Because hydrogen and fluorine contained in the C 4 H 3 F 7 O isomers produce volatile products such as FCN and HCN, the chemical sputtering threshold energy of Si 3 N 4 is lower than that of SiO 2 . , The ALE window regions were observed at bias voltages ranging from 50–60 V, as in the case of SiO 2 , and the EPC of Si 3 N 4 in the ALE window regions was determined to be 3.2, 3.3, and 40.3 Å/cycle for HFE-347mcc3, HFE-347mmy, and PPC, respectively. Because of the hydrogen content, all C 4 H 3 F 7 O isomers have a higher EPC of Si 3 N 4 than SiO 2 . , Because the C–F bond of the fluorocarbon layer in the PPC plasma produces FCN, a reaction byproduct of Si 3 N 4 , the EPC of Si 3 N 4 in the PPC plasma, is highest in the C 4 H 3 F 7 O isomer plasmas.…”

Section: Resultsmentioning

confidence: 99%

“…Because of the hydrogen content, all C 4 H 3 F 7 O isomers have a higher EPC of Si 3 N 4 than SiO 2 . 65,66 Because the C−F bond of the fluorocarbon layer in the PPC plasma produces FCN, a reaction byproduct of Si 3 N 4 , the EPC of Si 3 N 4 in the PPC plasma, is highest in the C 4 H 3 F 7 O isomer plasmas.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Plasma Atomic Layer Etching of SiO₂ and Si₃N₄ with Low Global Warming C₄H₃F₇O Isomers

Kang

ACS Sustainable Chem. Eng.

et al. 2023

In this study, plasma atomic layer etching (ALE) of C 4 H 3 F 7 O isomers heptafluoropropyl methyl ether (HFE-347mcc3), heptafluoroisopropyl methyl ether (HFE-347mmy), and perfluoro propyl carbinol (PPC) having low global warming potential were investigated and developed for SiO 2 and Si 3 N 4 films. Fluorocarbons generated from C 4 H 3 F 7 O isomer plasmas were used to fluorinate the SiO 2 and Si 3 N 4 surfaces, and the fluorinated surface was etched using Ar plasmas in the following step. The HFE-347mmy produces the lowest F 1s/C 1s ratio or carbon-rich fluorocarbon. The chemical sputtering threshold energy of Si 3 N 4 was found to be 5−10 V lower than that of SiO 2 . The ALE window was observed in the range of 50−60 V for all isomers, and the EPC of SiO 2 was determined to be 2.1, 1.8, and 5.2 Å/cycle for HFE-347mcc3, HFE-347mmy, and PPC, respectively. The EPC of Si 3 N 4 is higher than that of SiO 2 in all precursors. The highest etch selectivity of SiO 2 and Si 3 N 4 over poly-Si was achieved with HFE-347mmy as high as 103 for SiO 2 to poly-Si and 189 for Si 3 N 4 to poly-Si. This study demonstrates that C 4 H 3 F 7 O isomers can help reduce global warming by replacing the conventional perfluorocarbons and achieving high selectivity of SiO 2 to poly-Si and Si 3 N 4 to poly-Si.