Isotropic atomic layer etchings of various materials by using dry chemical removal

Ohtake, Hiroto; Miyoshi, Norikazu; Shinoda, Kazunori; Fujisaki, Seiichiro; Yamaguchi, Y.

doi:10.35848/1347-4065/acaed0

Cited by 8 publications

(6 citation statements)

References 35 publications

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“…26,34 275 °C was also above the thermal desorption temperature of ammonium hexafluorosilicate [(NH 4 ) 2 SiF 6 ] salt that can form during spontaneous etching of both SiN x and SiO 2 . 17,35 In addition, 275 °C was below the decomposition temperature of TMA around 300 °C. 36,37 2.1.…”

Section: Methodsmentioning

confidence: 99%

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Selectivity between SiO₂ and SiN_x during Thermal Atomic Layer Etching Using Al(CH₃)₃/HF and Spontaneous Etching Using HF and Effect of HF + NH₃ Codosing

Junige,

George

2024

Chem. Mater.

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Selectivity was examined between SiO 2 and SiN x during thermal atomic layer etching (ALE) and spontaneous etching. Thermal ALE of SiO 2 and SiN x was explored using sequential trimethylaluminum (TMA) and hydrogen fluoride (HF) with reactant exposures of 3 Torr for 45 s at 275 °C. SiO 2 thermal ALE achieved an etch per cycle (EPC) of 0.20 Å/cycle and near-ideal synergy up to 95%. SiN x thermal ALE exhibited a higher EPC of 1.06 Å/cycle. The selectivity factor was ∼5:1 for SiN x etching compared to SiO 2 etching (preferential SiN x removal) during thermal ALE using TMA and HF. Spontaneous etching was then quantified using repeated exposures of HF vapor alone at 3 Torr and 275 °C. SiO 2 spontaneous etching was minor at an etch rate of 0.03 Å/min, enabling near-ideal synergy for SiO 2 thermal ALE. In contrast, major SiN x spontaneous etching displayed an etch rate of 1.72 Å/min and predominated over SiN x thermal ALE. The selectivity factor was ∼50:1 for SiN x spontaneous etching compared to SiO 2 spontaneous etching using an HF pressure of 3 Torr. This selective SiN x spontaneous etching was attributed to F − surface species during HF exposures. NH 3 codosing with HF was then examined during thermal ALE and spontaneous etching. Thermal ALE of SiO 2 and SiN x was examined using sequential TMA and HF + NH 3 codosing with reactant exposures of 3 Torr for 45 s at 275 °C. SiO 2 thermal ALE with HF + NH 3 codosing had a high EPC of 8.83 Å/cycle. In contrast, SiN x thermal ALE with HF + NH 3 codosing was negligible. The selectivity factor was reversed and much higher at >1000:1 for SiO 2 etching compared to SiN x etching (preferential SiO 2 removal) during thermal ALE with HF + NH 3 codosing. Rapid SiO 2 spontaneous etching with HF + NH 3 codosing at 3 Torr had an etch rate of 27.50 Å/min. In contrast, SiN x spontaneous etching with HF + NH 3 codosing produced a very low etch rate of 0.02 Å/min. The selectivity factor was >1000:1 for SiO 2 spontaneous etching compared to SiN x spontaneous etching with HF + NH 3 codosing. This selective SiO 2 spontaneous etching was attributed to HF 2 − surface species during HF + NH 3 exposures. These studies revealed that the NH 3 coadsorbate during HF exposures modified the active etch species and dramatically influenced the etch selectivity between SiO 2 and SiN x . Reciprocal etch selectivity should be important for the selective removal of SiO 2 or SiN x in composite structures.

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Section: Methodsmentioning

confidence: 99%

“…Atomic layer control of dry thermal etching can be obtained using atomic layer etching (ALE) methods. − ALE employs an alternating sequence of separate self-limiting surface reactions. The first reaction typically modifies the surface and the second reaction volatilizes the modified surface layer .…”

Section: Introductionmentioning

confidence: 99%

Selectivity between SiO₂ and SiN_x during Thermal Atomic Layer Etching Using Al(CH₃)₃/HF and Spontaneous Etching Using HF and Effect of HF + NH₃ Codosing

Junige,

George

2024

Chem. Mater.

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“…To study plasma-induced compressive stress, blanket TiN films were exposed to the p-SiOCH etch plasma in the M-ECR system and subsequently etched with an inductively coupled plasma-type chemical dry removal (DCR) system 19 with Cl 2 gas chemistry 20 . The DCR system removed the top layer of TiN that was damaged during M-ECR processing, avoiding further surface damage due to the absence of ion bombardment.…”

Section: Blanket Evaluationmentioning

confidence: 99%

Evaluation of TiN hardmask films to prevent line wiggling due to plasma-induced film stress

Turnquist

Kofuji

Strzalka

et al. 2023

Advanced Etch Technology and Process Integration for Nanopatterning XII

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The impact of both intrinsic and plasma-induced stress of a TiN hardmask on line wiggling was investigated via etching of p-SiOCH with 28 nm pitch, line and space (L/S) EUV resist patterning. Experimental stacks included crystalline PVD TiN with an intrinsic stress of +0.1 GPa and several PEALD TiN films with varying crystallinity and intrinsic stresses ranging from -3.6 GPa (compressive) to +0.2 GPa (tensile). Results confirmed that reduction of intrinsic TiN stress can prevent wiggling1 when the mask is not exposed to plasma during process flow. However, when TiN is exposed to plasma as in a typical back end of line (BEOL) process2-3, compressive stress increased in all films and resulted in wiggling even in the patterned PVD TiN sample with low intrinsic stress. This global increase in compressive stress due to plasma exposure did not correlate with intrinsic stress values, therefore, this work suggests a greater focus should be placed on plasma-induced stress to avoid line wiggling when selecting a TiN film. Further investigation found that increased surface roughness of the TiN mask can decrease the risk of wiggling, and that surface roughness is influenced by p-SiOCH etch selectivity, indicating mask surface roughness should also be considered when evaluating line wiggling in BEOL, p-SiOCH etching.

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“…However, there are some concerns for future generations of devices, such as pattern collapse, water marking and insufficient etching in the bottom of a high-aspect structure [14][15][16] We may have two options for conformal etching in a dry process. One is the modification self-limiting process and the other is the surface reaction-limited process 17,18) The first is sometimes called atomic-layer etching (ALE) as removal occurs layer by layer [19][20][21] In this process, modification stops automatically at a certain depth due to reaction limitation, and the layer can be removed conformally if there is highly selective etching of the modified layer to the underlying layer. This technology has advantages such as high conformity and high selectivity; however, it is generally very slow for mass fabrication.…”

Section: Introductionmentioning

confidence: 99%

Etching selectivity of SiO₂ to SiN using HF and methanol at higher pressures up to 900 Pa

Hattori,

Kobayashi,

Ohtake

et al. 2024

Jpn. J. Appl. Phys.

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The isotropic gas-phase etching of SiO2 was examined using HF and methanol vapor while changing the pressure from 300 Pa to 900 Pa. The temperature dependence of the etching rate of SiO2 showed a broad maximum around –30 °C, and the rate increased with increasing the pressure. The etching rate of plasma-enhanced chemical vapor deposition (PE-CVD) SiO2 became more than 60 nm/min at 900 Pa at –30 °C. When the pressure was increased from 300 Pa to 900 Pa, the temperature range that indicates the SiO2 etching was shifted to a higher temperature. The etching of SiO2, which did not proceed at 300 Pa, was found to proceed even at 0 °C at 900 Pa. The etching rate of PE-CVD SiN was also found to slightly increase with the pressure. At the higher pressure of 900 Pa, the formation of ammonium hexafluorosilicate, which is byproduct of SiN, was found to increase. As a result, the high selectivity of more than twenty was obtained at the lower pressure of less than 600 Pa and the lower temperature of less than –40 °C.

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Isotropic atomic layer etchings of various materials by using dry chemical removal

Cited by 8 publications

References 35 publications

Selectivity between SiO₂ and SiN_x during Thermal Atomic Layer Etching Using Al(CH₃)₃/HF and Spontaneous Etching Using HF and Effect of HF + NH₃ Codosing

Selectivity between SiO₂ and SiN_x during Thermal Atomic Layer Etching Using Al(CH₃)₃/HF and Spontaneous Etching Using HF and Effect of HF + NH₃ Codosing

Evaluation of TiN hardmask films to prevent line wiggling due to plasma-induced film stress

Etching selectivity of SiO₂ to SiN using HF and methanol at higher pressures up to 900 Pa

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Isotropic atomic layer etchings of various materials by using dry chemical removal

Cited by 8 publications

References 35 publications

Selectivity between SiO2 and SiNx during Thermal Atomic Layer Etching Using Al(CH3)3/HF and Spontaneous Etching Using HF and Effect of HF + NH3 Codosing

Selectivity between SiO2 and SiNx during Thermal Atomic Layer Etching Using Al(CH3)3/HF and Spontaneous Etching Using HF and Effect of HF + NH3 Codosing

Evaluation of TiN hardmask films to prevent line wiggling due to plasma-induced film stress

Etching selectivity of SiO2 to SiN using HF and methanol at higher pressures up to 900 Pa

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Selectivity between SiO₂ and SiN_x during Thermal Atomic Layer Etching Using Al(CH₃)₃/HF and Spontaneous Etching Using HF and Effect of HF + NH₃ Codosing

Selectivity between SiO₂ and SiN_x during Thermal Atomic Layer Etching Using Al(CH₃)₃/HF and Spontaneous Etching Using HF and Effect of HF + NH₃ Codosing

Etching selectivity of SiO₂ to SiN using HF and methanol at higher pressures up to 900 Pa