Beam study of the Si and SiO2 etching processes by energetic fluorocarbon ions

Toyoda, Hirotaka; Morishima, Hajime; Fukute, R.; Hori, Y.; Murakami, Izumi; Sugai, Hideo

doi:10.1063/1.1690094

Cited by 25 publications

(13 citation statements)

References 19 publications

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“…These behaviours are in good agreement with experimental data obtained by Toyoda et al [25]. In their experiments, a 100 eV mass-selected CF þ 3 beam continuously bombarded silicon surfaces.…”

Section: Resultssupporting

confidence: 91%

CF3 interaction with Si(100)-(2×1): Molecular dynamics simulation

2007

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In this study, molecular dynamics simulations of CF 3 molecules interacting with the Si(1 0 0)-(2 · 1) surface were carried out using the improved Tersoff-Brenner potentials proposed by Humbird and Graves. They developed these potentials to provide a more accurate description of the Si-F interaction. We utilize these potentials to simulate the energy-dependent interaction of CF 3 with silicon. Properties such as the Si etch yield, the composition and nature of the reaction layer formed on the surface and the bond densities are discussed. The results show that the density of Si-C bonds in the reaction layer does not decrease as a result of Si etching (for the exposures studied). CF 2 is the dominant form of fluorocarbon present and its abundance remains constant over the course of the simulation; SiF is the main fluorosilyl species present. The depth profiles of SiF x and CF x in the reaction layer are shown and the desorption of etch products is discussed.

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Section: Resultssupporting

confidence: 91%

CF3 interaction with Si(100)-(2×1): Molecular dynamics simulation

2007

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“…8 The apparatus is composed of four parts: an ion beam source for Ar + beam production, a monochromated XPS system for the surface analysis, and a quadrupole mass spectrometer (QMA) for detection of surface-produced species, although the QMA is not used in the present experiment. A base pressure of ϳ10 −9 Torr is obtained with use of four turbomolecular pumps at a total pumping speed of ϳ2000 l / s. In the beam source, Ar + beam is generated by electron-impact ionization of Ar and by mass selection of a singly charged Ar ion with a quadrupole mass filter.…”

Section: Methodsmentioning

confidence: 99%

“…On the other hand, beam experiments using a selected species with controlled incident energy are suitable for basic study of surface reactions. [8][9][10][11][12] Recently, various kinds of fluorocarbon etching gases have been developed to achieve a high etch selectivity of SiO 2 / Si and to avoid a greenhouse effect. Mostly, such fluorocarbon gases are carbon rich in the atomic composition, such as C 4 F 8 or C 5 F 8 .…”

Section: Introductionmentioning

confidence: 99%

Evidence of direct SiO2 etching by fluorocarbon molecules under ion bombardment

Toyoda

Murakami

Sugai

2004

Journal of Applied Physics

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In a beam apparatus, influence of fluorocarbon gas (C5F8, C4F8, and CF4 molecules) flux onto SiO2 etching reaction is investigated in comparison to a case of CF2 radical flux. Fluorocarbon molecules or CF2 radicals are incident onto SiO2 surface with Ar+ beam of energy 100–900eV. Atomic composition of SiO2 surface under the ion and molecule incidence is measured by in situ x-ray photoelectron spectroscopy. Fluorocarbon∕Ar+ co-incidence enhances the SiO2 etching compared with pure Ar+ incidence, suggesting the etching effect of fluorocarbon molecules under Ar+ bombardment. In the case of C5F8∕Ar+ co-incidence, formation of fluorocarbon layer is observed as the case of CF2∕Ar+ co-incidence. Etching yields of SiO2 by C5F8∕Ar+ and CF2∕Ar+ co-incidences are measured for different Ar+ incident energies and fluorocarbon∕Ar+ flux ratios. The etching yield increases monotonically with the Ar+ incident energy, and reaches the value of 2.4 at 900eV in case of C5F8, which is about 1.5 times as high as in the CF2 case. In the case of C5F8 and CF2, a phenomenon like etch stop, with formation of a thick fluorocarbon layer, is observed for larger fluorocarbon flux, with the threshold of the fluorocarbon∕Ar+ flux, ratio between 2.5 and 25. These results suggest a significant contribution of direct SiO2 etching by fluorocarbon molecules in practical etching reactors, especially in case of the C5F8 molecule.

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“…13,14 Energy-controlled and mass-selected CF 2 + and CF 3 + ion beams were used with the goal of controlling the surface atomic composition and so controlling the removal rate of SiO 2 . 15,16 Increasing the ion beam energy from 100 to 400 eV increased the F/O ratio of the surface layers due to enhanced surface fluorination and produced a higher etch yield of SiO 2 . Extremely high ion energies (several keV) damage SiO 2 and the underlying Si according to both experiments and numerical simulations.…”

Section: Introductionmentioning

confidence: 99%

Plasma etching of high aspect ratio features in SiO2 using Ar/C4F8/O2 mixtures: A computational investigation

Huang

Huard

Shim

et al. 2019

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

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Plasma etching of high aspect ratio (HAR) features, typically vias, is a critical step in the fabrication of high capacity memory. With aspect ratios (ARs) exceeding 50 (and approaching 100), maintaining critical dimensions (CDs) while eliminating or diminishing twisting, contact-edge-roughening, and aspect ratio dependent etching (ARDE) becomes challenging. Integrated reactor and feature scale modeling was used to investigate the etching of HAR features in SiO 2 with ARs up to 80 using tri-frequency capacitively coupled plasmas sustained in Ar/C 4 F 8 /O 2 mixtures. In these systems, the fluxes of neutral radicals to the wafer exceed the fluxes of ions by 1-2 orders of magnitude due to lower threshold energies for dissociation compared with ionization. At low ARs (<5), these abundant fluxes of CF x and C x F y radicals to the etch front passivate the oxide to form a complex which is then removed by energetic species (ions and hot neutrals) through chemically enhanced reactive etching, resulting in the formation of gas phase SiF x , CO x , and COF. As the etching proceeds into higher ARs, the fractional contribution of physical sputtering to oxide removal increases as the fluxes of energetic species to the etch front surpass those of the conduction constrained CF x and C x F y radicals. The instantaneous etch rate of oxide decreases with increasing aspect ratio (ARDE effect) due to decreased fluxes of energetic species and decreased power delivered by these species to the etch front. As the etch rate of photoresist (PR) is independent of AR, maintaining CDs by avoiding undercut and bowing requires high SiO 2-over-PR selectivity, which in turn requires a minimum thickness of the PR at the end of etching. Positive ions with narrow angular distributions typically deposit charge on the bottom of low AR features, producing a maximum in positive electric potential on the bottom of the feature. For high AR features, grazing incidence collisions of ions on sidewalls depositing charge produce electric potentials with maxima on the sidewalls (as opposed to the bottom) of the feature.

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Beam study of the Si and SiO2 etching processes by energetic fluorocarbon ions

Cited by 25 publications

References 19 publications

CF3 interaction with Si(100)-(2×1): Molecular dynamics simulation

CF3 interaction with Si(100)-(2×1): Molecular dynamics simulation

Evidence of direct SiO2 etching by fluorocarbon molecules under ion bombardment

Plasma etching of high aspect ratio features in SiO2 using Ar/C4F8/O2 mixtures: A computational investigation

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