Controlled ALE-type recess of molybdenum for future logic and memory applications

Pacco, Antoine; Nakano, Teppei; Iwasaki, Akihisa; Iwahata, Shota; Sánchez, Efrain Altamirano

doi:10.1109/iitc51362.2021.9537407

Cited by 4 publications

(8 citation statements)

References 5 publications

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“…Other elemental metals that are considered for nanoscale conductors include Rh [ 38 , 39 ], Ir [ 40 , 41 ], and Ru [ 42 , 43 , 44 ]. They have 46%, 38%, and 15% smaller ρ o λ products than Mo [ 34 ], respectively, but are challenging due to cost, small earth abundance, and limited process maturity [ 45 , 46 , 47 ].…”

Section: Introductionmentioning

confidence: 99%

Anisotropic Resistivity Size Effect in Epitaxial Mo(001) and Mo(011) Layers

et al. 2023

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Mo(001) and Mo(011) layers with thickness d = 4–400 nm are sputter-deposited onto MgO(001) and α-Al2O3(112¯0) substrates and their resistivity is measured in situ and ex situ at room temperature and 77 K in order to quantify the resistivity size effect. Both Mo(001) and Mo(011) layers are epitaxial single crystals and exhibit a resistivity increase with decreasing d due to electron surface scattering that is well described by the classical Fuchs and Sondheimer model. Data fitting yields room temperature effective electron mean free paths λ*= 14.4 ± 0.3 and 11.7 ± 0.3 nm, respectively, indicating an anisotropy with a smaller resistivity size effect for the Mo(011) orientation. This is attributed to a smaller average Fermi velocity component perpendicular to (011) surfaces, causing less surface scattering and a suppressed resistivity size effect. First-principles electronic structure calculations in combination with Boltzmann transport simulations predict an orientation dependent transport with a more pronounced resistivity increase for Mo(001) than Mo(011). This is in agreement with the measurements, confirming the effect of the Fermi surface shape on the thin-film resistivity. The predicted anisotropy λ001*/λ011* = 1.57 is in reasonable agreement with 1.66 and 1.23 measured at 77 and 295 K. The overall results indicate that the resistivity size effect in Mo is relatively small, with a measured product of the bulk resistivity times the effective electron mean free path ρoλ* = (7.7 ± 0.3) and (6.2 ± 0.2) × 10−16 Ωm2 for Mo(001) and Mo(011) layers. The latter value is in excellent agreement with the first-principles-predicted ρoλ = 5.99 × 10−16 Ωm2 and is 10% and 40% smaller than the reported measured ρoλ for Cu and W, respectively, indicating the promise of Mo as an alternate conductor for narrow interconnects.

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Section: Introductionmentioning

confidence: 99%

Anisotropic Resistivity Size Effect in Epitaxial Mo(001) and Mo(011) Layers

et al. 2023

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“…[20][21][22][23] A two-step approach involving selflimiting metal oxidation followed by selective oxide dissolution has been proposed for better etching control. [16,24] Nonetheless, self-limiting wet oxidation of Mo has not yet been achieved, with only thermal oxidation currently available. [16] Here, we explored the dynamics of wet etching of polycrystalline Mo NWs with hydrogen peroxide (H 2 O 2 ) solutions.…”

Section: Introductionmentioning

confidence: 99%

“…[16,24] Nonetheless, self-limiting wet oxidation of Mo has not yet been achieved, with only thermal oxidation currently available. [16] Here, we explored the dynamics of wet etching of polycrystalline Mo NWs with hydrogen peroxide (H 2 O 2 ) solutions. We tracked the direct etching of the Mo NWs with 1% (v/v) H 2 O 2 aqueous solution using in situ liquid phase transmission electron microscopy (LP-TEM) [19,23,25] and observed the formation of etching non-uniformities, in particular at the GBs.…”

Section: Introductionmentioning

confidence: 99%

“…[ 1,4,6,11–15 ] Chemical wet etching is the fabrication step that affects uniformity and surface roughness of metal NWs the most, so it is imperative to achieve a smooth (isotropic), atomic‐level controlled, and selective etching process. [ 16 ] Nevertheless, controlled and uniform wet etching of nanocrystalline Mo NWs is challenging because of the varying etching rates for different grain orientations and GBs. Hence, understanding and developing reliable wet etching processes for nanocrystalline metals such as Mo is critical for the future fabrication of semiconductor devices.…”

Section: Introductionmentioning

confidence: 99%

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Controlled Stepwise Wet Etching of Polycrystalline Mo Nanowires

Saidov,

Erofeev,

Aabdin

et al. 2023

Adv Funct Materials

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With the persistent downscaling of integrated circuits, molybdenum (Mo) is currently considered a potential replacement for copper (Cu) as a material for metal interconnects. However, fabricating metal nanostructures with critical dimensions of the order of 10 nm and below is challenging. This is because the very high density of grain boundaries (GBs) results in highly non‐uniform surface profiles during direct wet etching. Moreover, wet etching of Mo with conventional aqueous solutions is problematic, as products of Mo oxidation have different solubility in water, which leads to increased surface roughness. Here, a process is shown for achieving a stable and uniform soluble surface layer of Mo oxide by wet oxidation with H2O2 dissolved in IPA at −20 °C. The oxide layer is then selectively dissolved, and by repeating the oxidation and dissolution multiple times, a uniform etch profile is demonstrated with a fine control over the metal recess. Ultimately, this presents a method of precise and uniform wet etching for Mo and other metals needed to fabricate complex nanostructures that are critical in developing next‐generation electronic devices.

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“…To minimize surface roughness, a new cyclic process of dry oxidation followed by wet etching has been developed, so the oxidation and etching reactions are separated. In the oxidation step, a homogeneous oxide layer is formed by baking in ozone (O3) gas and then selectively etched by subsequent wet chemistry which doesn't contain any oxidant (6). In this paper, the development of the Mo recess process using a higher baking temperature to increase the recess depths is disclosed.…”

Section: Introductionmentioning

confidence: 99%

A Novel Method For Molybdenum Etching Using a Combination of Surface Oxidation By Ozone-Gas-Bake and Wet Selective Removal for Future Semiconductor Devices

Nakano¹,

Pacco²,

Iwahata³

et al. 2022

ECS Trans.

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As semiconductor devices continue to scale, it is important to evaluate new metals for narrower trench or via structures. Mo is a candidate because of its lower resistivity compared to the conventional metals, Cu or W. Mo is etched with wet chemistry using an oxidizer but increase in surface roughness is a problem. The model for increase in roughness is water insoluble MoO2 partially remains whereas MoO3 dissolves in the water via simultaneous "oxidation-dissolution" reactions. We have developed a novel cyclic process with O3 gas bake followed by oxidizer free wet process to separate the oxidation and dissolution and verified that surface roughness does not increase. The new process was tested with patterned wafer to look at residue on sidewall, pattern loading and oxygen diffusion. This method is showing promising results and is expected to be applied for use in manufacturing of future semiconductor devices.

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Controlled ALE-type recess of molybdenum for future logic and memory applications

Cited by 4 publications

References 5 publications

Anisotropic Resistivity Size Effect in Epitaxial Mo(001) and Mo(011) Layers

Anisotropic Resistivity Size Effect in Epitaxial Mo(001) and Mo(011) Layers

Controlled Stepwise Wet Etching of Polycrystalline Mo Nanowires

A Novel Method For Molybdenum Etching Using a Combination of Surface Oxidation By Ozone-Gas-Bake and Wet Selective Removal for Future Semiconductor Devices

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