Atomic layer etching of silicon dioxide using alternating C4F8and energetic Ar+plasma beams

Kaler, Sanbir; Lou, Qiaowei; Donnelly, Vincent M.; Economou, Demetre J.

doi:10.1088/1361-6463/aa6f40

Cited by 41 publications

(30 citation statements)

References 32 publications

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“…One of the main solutions to perform anisotropic ALE of SiO 2 is to use fluorocarbon-based plasmas to deposit a very thin FC modified layer on the surface. This layer can then be etched using Ar or O 2 plasma at low ion energy bombardment 2,3,[6][7][8][9][10][11] . However, some drifts were reported in the processes, with an increase of the etch amount per cycle (EPC) due to the fluorine contamination of the reactor walls [8][9][10]12 .…”

mentioning

confidence: 99%

Mechanism understanding in cryo atomic layer etching of SiO2 based upon C4F8 physisorption

Antoun

Tillocher

Lefaucheux

et al. 2021

Sci Rep

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Cryogenic Atomic Layer Etching (cryo-ALE) of SiO2 based on alternating a C4F8 molecule physisorption step and an argon plasma step, has been enhanced thanks to a better understanding of the mechanism. First, we used Quadrupole Mass spectrometry (QMS) and spectroscopic ellipsometry analyses to evaluate the residence time of physisorbed C4F8 molecules versus temperature and pressure on SiO2 surface. QMS monitoring of the SiF4 etching by-product also enabled to follow the self-limiting etching behavior. Finally, a SiO2 cryo-ALE process was proposed at a temperature of − 90 °C resulting in a very linear etch over 150 cycles and an Etch amount Per Cycle as low as 0.13 nm/cycle.

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mentioning

confidence: 99%

Mechanism understanding in cryo atomic layer etching of SiO2 based upon C4F8 physisorption

Antoun

Tillocher

Lefaucheux

et al. 2021

Sci Rep

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show abstract

“…These sticking coefficients are similar to those obtained recently by Kaler et al in cyclic plasma beam exposure experiments. 51 The transfer of ion energy through the polymer overlayer to the etch front is critical to this etch mechanism. Which energetic particles carry the activation energy to the etch front is difficult to analyze.…”

Section: Surface Reaction Mechanism For Sio 2 Si 3 N 4 and Smentioning

confidence: 99%

“…Kaler et al have also observed this effect and proposed that it may be utilized to produce pseudo-self-limiting behavior. 51 The second process which results in the erosion of SiO 2 occurs during the ion bombardment phase. This erosion occurs as SiO 2 is converted to selvedge species by mixing with polymer when activated by ions penetrating through the polymer capping layer.…”

Section: Ale Blanket Etchingmentioning

confidence: 99%

Transient behavior in quasi-atomic layer etching of silicon dioxide and silicon nitride in fluorocarbon plasmas

Huard

Sriraman

Paterson

et al. 2018

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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The mechanism for atomic layer etching (ALE) typically consists of two sequential self-limited half-reactions-passivation and ion bombardment-which provide unique control over the process. Some of the possible benefits of this control include increased selectivity, reduced plasma induced damage, improved uniformity and aspect ratio independence. To achieve the greatest benefit from ALE, both half-reactions should be fully self-limited. In the experimental demonstration of ALE of SiO 2 using fluorocarbon plasmas, the passivation phase typically consists of deposition of fluoropolymer on the SiO 2 surface. This passivation step is not a self-limited reaction as the final polymer thickness depends on the passivation time. In this paper, results are presented from a computational investigation of the ALE of SiO 2 and Si 3 N 4 focusing on the implications of this nonself-limited passivation phase. The polymer overlayer was found to be critically important to the ALE performance, providing the main mechanism for selectivity between SiO 2 and Si 3 N 4. The polymer overlayer acts as a fuel for etching SiO 2 , which couples the etch depth per ALE cycle to the passivation time. Due to the inherently pulsed nature of the ALE mechanism, the polymer overlayer requires a finite number of cycles to reach a pulsed periodic steady-state thickness. Since the thickness of the polymer overlayer largely determines selectivity between SiO 2 and Si 3 N 4 , the initial formation of an overlayer results in a transient period at the beginning of etching where high selectivity may not be achieved. For the etching of thin films, or applications which require very high selectivity, this transient etching period may be a limiting factor. Results are also presented using ALE to etch high aspect ratio self-aligned contacts which could not be cleared using continuous plasma etching with similar ion energies and flux ratios.

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“…Using these techniques, a precise etch depth/cycle of various semiconductor related materials such as Si, III‐V compounds, metals, and 2D materials has been achieved . As the plasma sources for radical adsorption, inductively coupled plasma (ICP) and capacitively coupled plasma (CCP) were mainly used while, as the desorption sources, an ion/neutral beam or conventional radio frequency (RF) biasing was used for anisotropic ALE technology. Recently, for the fabrication of nanoscale devices, in addition to the anisotropic ALE, isotropic ALE or also known as thermal ALE, where, materials are etched the same in all direction isotropically, is actively investigated.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic atomic layer etching of W using fluorine radicals/oxygen ion beam

Kim

Lee

et al. 2019

Plasma Processes & Polymers

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Atomic layer etching (ALE) has advantages such as precise thickness control, high etch selectivity, and no‐increase in surface roughness which can be applied to sub 10 nm semiconductor device fabrication. In this study, anisotropic ALE of tungsten (W), which is used as an interconnect layer and gate material of semiconductor devices, was investigated by sequentially exposing to F radicals by NF3 plasma to form a WFy layer and following exposure to an oxygen ion beam to remove the WFy layer by forming volatile WOxFy at room temperature. A wide ALE window of F radical adsorption time of ( ≥ 10 s/cycle) and Ox+ ion desorption time of (10 ≤ t ≤ 50 s/cycle at + 44–51 eV of Ox+ ion energy) could be identified, and at the ALE conditions, a precise etch rate of ~2.6 Å/cycle was obtained while increasing the W etch depth linearly with increasing the number of etch cycles. At the optimized W ALE conditions, the W surface roughness after the W ALE was similar to the as‐received W and the etch selectivity over SiO2 was close to infinite. However, after the W ALE, ~ 10% F diffused into W was observed on the etched W surface, and which could be removed by a following process.

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Atomic layer etching of silicon dioxide using alternating C₄F₈and energetic Ar⁺plasma beams

Cited by 41 publications

References 32 publications

Mechanism understanding in cryo atomic layer etching of SiO2 based upon C4F8 physisorption

Mechanism understanding in cryo atomic layer etching of SiO2 based upon C4F8 physisorption

Transient behavior in quasi-atomic layer etching of silicon dioxide and silicon nitride in fluorocarbon plasmas

Anisotropic atomic layer etching of W using fluorine radicals/oxygen ion beam

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