Tungsten Etching in  CF 4 and  SF 6 Discharges

Tang, C. C. H.; Hess, Dennis W.

doi:10.1149/1.2115489

Cited by 81 publications

(26 citation statements)

References 11 publications

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“…W and WO 3 can also be etched spontaneously using various dry etching techniques. Methods for spontaneous tungsten etching utilize plasmas containing various halogens such as fluorine − or chlorine. ,, Tungsten etching occurs through formation of volatile chlorides or fluorides. Tungsten can also be etched by Cl 2 or XeF 2 gases. ,, WO 3 can be etched spontaneously with halogen-containing plasmas using NF 3 or SF 6 . − WF 6 is also known to etch WO 3 spontaneously at >180 °C from WO 3 ALD studies using WF 6 and H 2 O as the reactants. , This spontaneous etching of WO 3 by WF 6 suggests a pathway for W ALE based on sequential reactions with W oxidation followed by WF 6 exposures to remove WO 3 .…”

Section: Introductionmentioning

confidence: 99%

WO₃ and W Thermal Atomic Layer Etching Using “Conversion-Fluorination” and “Oxidation-Conversion-Fluorination” Mechanisms

Johnson

George

2017

ACS Appl. Mater. Interfaces

117

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The thermal atomic layer etching (ALE) of WO and W was demonstrated with new "conversion-fluorination" and "oxidation-conversion-fluorination" etching mechanisms. Both of these mechanisms are based on sequential, self-limiting reactions. WO ALE was achieved by a "conversion-fluorination" mechanism using an AB exposure sequence with boron trichloride (BCl) and hydrogen fluoride (HF). BCl converts the WO surface to a BO layer while forming volatile WOCl products. Subsequently, HF spontaneously etches the BO layer producing volatile BF and HO products. In situ spectroscopic ellipsometry (SE) studies determined that the BCl and HF reactions were self-limiting versus exposure. The WO ALE etch rates increased with temperature from 0.55 Å/cycle at 128 °C to 4.19 Å/cycle at 207 °C. W served as an etch stop because BCl and HF could not etch the underlying W film. W ALE was performed using a three-step "oxidation-conversion-fluorination" mechanism. In this ABC exposure sequence, the W surface is first oxidized to a WO layer using O/O. Subsequently, the WO layer is etched with BCl and HF. SE could simultaneously monitor the W and WO thicknesses and conversion of W to WO. SE measurements showed that the W film thickness decreased linearly with number of ABC reaction cycles. W ALE was shown to be self-limiting with respect to each reaction in the ABC process. The etch rate for W ALE was ∼2.5 Å/cycle at 207 °C. An oxide thickness of ∼20 Å remained after W ALE, but could be removed by sequential BCl and HF exposures without affecting the W layer. These new etching mechanisms will enable the thermal ALE of a variety of additional metal materials including those that have volatile metal fluorides.

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Section: Introductionmentioning

confidence: 99%

WO₃ and W Thermal Atomic Layer Etching Using “Conversion-Fluorination” and “Oxidation-Conversion-Fluorination” Mechanisms

Johnson

George

2017

ACS Appl. Mater. Interfaces

117

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“…32 Because many metal halides are volatile (e.g., CrO 2 Cl 2 , TaF 5 , WF 6 , AlCl 3 ), halogen-based plasmas are typically used in plasma etching process. [33][34][35][36] However, Cu, Ag, and Au do not form volatile halogenated etch products in traditional halogen-based plasmas. [37][38][39] Therefore, alternative methods to enhance removal of product species have been applied to assist etch product removal; these methods include increased temperature, [39][40][41][42][43][44] enhancement of ion bombardment energy, 40,[45][46][47][48][49] photon exposure, 50,51 and wet etching to remove product species.…”

Section: Au(s)mentioning

confidence: 99%

Chemical Etching and Patterning of Copper, Silver, and Gold Films at Low Temperatures

Choi

Hess

2014

ECS J. Solid State Sci. Technol.

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Copper, silver, and gold share unique properties that offer numerous application possibilities. For instance, low resistivity and high electromigration resistance make them attractive as interconnect layers in integrated circuits and microelectronic devices, while the optical properties of their nano-scale structures allow fabrication of plasmonic devices. Etching or patterning techniques are required in order to fabricate nano-structures, devices, and circuits. Although liquid or vapor phase techniques can be applied, plasma or glow discharge methods are typically invoked due to the need to generate anisotropic nanometer pattern sizes. Group 11 metals (Cu, Ag, and Au) form few volatile compounds at temperatures below 150 • C, which limits the approaches that can be used to perform etching/patterning. Halogenated plasmas are widely used to etch metal layers; however, the low volatility of Cu, Ag, and Au halides precludes low temperature processes. Group 11 metals form hydrides readily in plasmas containing hydrogen species. Despite the thermodynamic instability of these metal hydrides, they appear to form at low (below room) temperature and can be desorbed from the etching surface by ion-or photon-assisted processes. Similarly, methylated metal etch products can be generated with hydrocarbon etching plasmas. As a result, etch rates above 12 ± 1 nm/min can be achieved, even when polymer forming plasmas (e.g., methane or other hydrocarbons) are used for patterning. These simple subtractive plasma etching approaches offer significant advantages relative to other vapor phase or liquid techniques in the manufacture of nano-scale devices and circuits.

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“…Nevertheless, it remains to be determined how SF6, as the primary precursor, affects the growth of CSxFy thin films, and resulting physical and mechanical properties. Also, even though the SF6 gas is a common dry etchant for Si-based (e.g., Si [30] and SiC [31]) or metallic (e.g., W [32]) materials in plasma processes, this gas is less reported as a single source for both F and S species in reactive deposition. Thus, studies dedicated to the precursor's dissociation and reaction behaviors, as well as the relationship between the obtained properties in the CSxFy films and the process parameters, are needed in order to understand the formation of the C-S-F networks in the reactive deposition process.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and properties of CS_xF_ythin films deposited by reactive magnetron sputtering in an Ar/SF₆discharge

Lai

Goyenola²,

Broitman³

et al. 2017

J. Phys.: Condens. Matter

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A theoretical and experimental study on the growth and properties of a ternary carbon-based material, CS F , synthesized from SF and C as primary precursors is reported. The synthetic growth concept was applied to model the possible species resulting from the fragmentation of SF molecules and the recombination of S-F fragments with atomic C. The possible species were further evaluated for their contribution to the film growth. Corresponding solid CS F thin films were deposited by reactive direct current magnetron sputtering from a C target in a mixed Ar/SF discharge with different SF partial pressures ([Formula: see text]). Properties of the films were determined by x-ray photoelectron spectroscopy, x-ray reflectivity, and nanoindentation. A reduced mass density in the CS F films is predicted due to incorporation of precursor species with a more pronounced steric effect, which also agrees with the low density values observed for the films. Increased [Formula: see text] leads to decreasing deposition rate and increasing density, as explained by enhanced fluorination and etching on the deposited surface by a larger concentration of F/F species during the growth, as supported by an increment of the F relative content in the films. Mechanical properties indicating superelasticity were obtained from the film with lowest F content, implying a fullerene-like structure in CS F compounds.

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Tungsten Etching in CF 4 and SF 6 Discharges

Cited by 81 publications

References 11 publications

WO₃ and W Thermal Atomic Layer Etching Using “Conversion-Fluorination” and “Oxidation-Conversion-Fluorination” Mechanisms

WO₃ and W Thermal Atomic Layer Etching Using “Conversion-Fluorination” and “Oxidation-Conversion-Fluorination” Mechanisms

Chemical Etching and Patterning of Copper, Silver, and Gold Films at Low Temperatures

Synthesis and properties of CS_xF_ythin films deposited by reactive magnetron sputtering in an Ar/SF₆discharge

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Tungsten Etching in CF 4 and SF 6 Discharges

Cited by 81 publications

References 11 publications

WO3 and W Thermal Atomic Layer Etching Using “Conversion-Fluorination” and “Oxidation-Conversion-Fluorination” Mechanisms

WO3 and W Thermal Atomic Layer Etching Using “Conversion-Fluorination” and “Oxidation-Conversion-Fluorination” Mechanisms

Chemical Etching and Patterning of Copper, Silver, and Gold Films at Low Temperatures

Synthesis and properties of CSxFythin films deposited by reactive magnetron sputtering in an Ar/SF6discharge

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WO₃ and W Thermal Atomic Layer Etching Using “Conversion-Fluorination” and “Oxidation-Conversion-Fluorination” Mechanisms

WO₃ and W Thermal Atomic Layer Etching Using “Conversion-Fluorination” and “Oxidation-Conversion-Fluorination” Mechanisms

Synthesis and properties of CS_xF_ythin films deposited by reactive magnetron sputtering in an Ar/SF₆discharge