Hot-wire-assisted atomic layer deposition of a high quality cobalt film using cobaltocene: Elementary reaction analysis on NH<i>x</i> radical formation

Shimizu, H.; Sakoda, Kaoru; Momose, Takeshi; Koshi, Mitsuo; Shimogaki, Yukihiro

doi:10.1116/1.3666034

Cited by 49 publications

(49 citation statements)

References 38 publications

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“…The dissociation of NH 3 by hot wire has been reported in the literature. 27 In our system, the reduction process by atomic hydrogen after half-reaction 5 prevails over the Ti-NH formation during half-reaction 6.…”

Section: P152mentioning

confidence: 98%

Hot-Wire Generated Atomic Hydrogen and its Impact on Thermal ALD in TiCl₄/NH₃System

Bui

Kovalgin

Aarnink

et al. 2013

ECS J. Solid State Sci. Technol.

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We present the generation of atomic hydrogen made by the dissociation of molecular hydrogen upon collision with a tungsten (W) filament kept at a high temperature (T ≈ 1600-1900 • C). We demonstrate the ability to create atomic hydrogen and to introduce it in short pulses in experiments on etching of tellurium (Te) films. We further utilize the generated atomic hydrogen (H) to explore its impact on surface reactions in the TiCl 4 /NH 3 precursor system. Atomic hydrogen is introduced in pulses additionally to TiCl 4 and NH 3 with different pulse sequences. For the TiCl 4 /NH 3 /H sequence, there is no influence on the process compared to the ALD without H-pulses. The growth rate remains at 0.02 nm/cycle and the oxygen (residual gas) content -at 3-5 at%. For the TiCl 4 /H/NH 3 pulse sequence, the growth rate decreases to 0.01 nm/cycle and the oxygen content increases to 30-35 at%. Only TiCl 4 /H pulses result in no growth after the formation of approximately one monolayer. Similar effect occurs after introducing NH 3 via the hot filament, pointing to the decomposition of NH 3 and the formation of atomic hydrogen.It has been projected in the International Technology Roadmap for Semiconductors (ITRS) that new materials will be intensively introduced, starting from 2018, to replace or to be integrated with silicon in integrated circuits. 1 The coming era of new materials naturally implies a development of new technologies, new processes, and new precursors. Atomic Layer Deposition (ALD) is an excellent example of a process to realize new materials.ALD has a constantly growing market for deposition of dielectric, semiconductor and metallic layers of various functionalities where excellent optical, mechanical, electrical or chemical properties are required. The most important advantage of ALD over other deposition techniques is its capability to deposit films of uniform thickness on arbitrarily shaped and patterned surfaces, and controlling the thickness with a very high precision. Thermal ALD processes are commonly used to deposit compounds. Single-element films of metals and semiconductors, which become increasingly important for industry, are however very difficult to deposit using thermal-only ALD processes. 2 A solution in this case is plasma-enhanced ALD (PEALD), also called radical-enhanced ALD (REALD). Hydrogen-or nitrogen-based plasmas are used for PEALD of Ta(N), Ti(N), Ru, Si and Ge, 3-11 Al 12 as well as AlN 13 and GaN. 14 Pt can be grown using remote O 2 plasmas; 15 PEALD of Al 2 O 3 demonstrates better film properties compared to the thermal process. 16,17 In this work, we explore an alternative technique to generate radicals without plasma. We choose processes where dissociation of a certain precursor to form radicals can be achieved due to collisions with a hot tungsten (W) filament heated up to a temperature in the range of 1600-1900 • C. A plasma-based source of atomic hydrogen is substituted by the hot-wire source. This ensures that only molecular and atomic hydrogen are present in the gas phase, i.e....

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Section: P152mentioning

confidence: 98%

Hot-Wire Generated Atomic Hydrogen and its Impact on Thermal ALD in TiCl₄/NH₃System

Bui

Kovalgin

Aarnink

et al. 2013

ECS J. Solid State Sci. Technol.

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“…As a matter of fact, publications related to HWALD are very rare in the literature. The few available works are on HWALD of Co(W) films , where ammonia gas is dissociated upon hot‐wire. Kostis et al introduced oxygen gas to oxidize hot tungsten filament and form volatile tungsten oxides.…”

Section: Introductionmentioning

confidence: 99%

Hot-wire assisted ALD of tungsten films:In-situstudy of the interplay between CVD, etching, and ALD modes

Yang

Aarnink

Kovalgin

et al. 2015

Phys. Status Solidi A

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In this work, we investigated an approach of hot‐wire assisted ALD (HWALD), utilizing a hot (up to 2000 °C) tungsten (W) wire. Tungsten films were deposited by this method using alternating pulses of WF6 gas and atomic hydrogen (at‐H). The latter was generated by catalytic dissociation of molecular hydrogen (H2) upon the hot‐wire. The W films were grown on a 100‐nm thick thermal SiO2. The growth process was monitored in real time by an in‐situ spectroscopic ellipsometer (SE). The real‐time SE monitoring revealed the coexistence of three processes: CVD, etching, and ALD of the W film. WF6 could back‐stream diffuse to the hot‐wire, resulting in WF6 decomposition and generation of a flux of fluorine (F). The latter caused etching of the grown W film and the filament, and provided extra tungsten supply, which might cause CVD. Higher pressure and higher carrier gas flow rate were found to largely suppress the back‐stream diffusion of WF6, which efficiently limited CVD. By controlling the dose of WF6 and process pressure, the etching had also been minimized. X‐ray photoelectron spectroscopy of optimized HWALD grown W revealed 99 at% of W; concentrations of oxygen and fluorine were lower than 1%, below the detection limit.

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“…Co thin-films can be fabricated using a variety of techniques, e.g., physical vapor deposition (PVD), 8,9 chemical vapor deposition (CVD), 10-13 vapor-phase atomic layer deposition (ALD), [14][15][16][17] and electroless deposition. 6,18-22 PVD, CVD, and ALD processes have several drawbacks including the use of expensive targets or unstable metal-organic precursors.…”

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confidence: 99%

“…6,7 At narrow dimensions, i.e., below 10 nm, Co exhibits comparable or lower electrical resistivity compared to Cu, largely attributed to the lower electron mean free path in Co (EMFP = 7-12 nm at room temperature). 7 Co thin-films can be fabricated using a variety of techniques, e.g., physical vapor deposition (PVD), 8,9 chemical vapor deposition (CVD), [10][11][12][13] vapor-phase atomic layer deposition (ALD), [14][15][16][17] and electroless deposition. 6,[18][19][20][21][22] PVD, CVD, and ALD processes have several drawbacks including the use of expensive targets or unstable metal-organic precursors.…”

mentioning

confidence: 99%

Electrochemical Atomic Layer Deposition of Cobalt Enabled by the Surface-Limited Redox Replacement of Underpotentially Deposited Zinc

Venkatraman

Dordi

Akolkar

2017

J. Electrochem. Soc.

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Electrochemical atomic layer deposition (e-ALD) process for fabricating cobalt (Co) nano-films is reported. The e-ALD process employs a two-step approach in which underpotential deposition (UPD) is first used to form a sacrificial adlayer of zinc (Zn) on a ruthenium (Ru) substrate. The sacrificial Zn adlayer then undergoes spontaneous surface-limited redox replacement (SLRR) by nobler Co. This provides an atomic layer of Co on the substrate surface. The two-step process is repeated cyclically to build multilayers of Co. The unique feature of the e-ALD approach presented herein is that it utilizes Zn as the sacrificial adlayer instead of Pb or Cu used conventionally in the e-ALD sequence of noble metals. The use of sacrificial Zn uniquely renders its redox replacement by Co to be thermodynamically favorable, thereby enabling Co e-ALD. In the present report, we discuss the electrochemical characteristics of the UPD and SLRR process steps, the e-ALD deposition rate and the deposit surface roughness. The Co deposits formed via e-ALD do not exhibit roughness amplification during the first 10 cycles of e-ALD, which is indicative of atomic-scale layer-by-layer growth of Co on the underlying Ru substrate. High-performance integrated circuits utilize nano-scale, currentcarrying copper (Cu) interconnects. In accordance with the Moore's law, 1 miniaturized interconnects are required in modern devices to obtain superior device performance. The continued shrinkage in the size (cross-sectional area) of each interconnect leads to an increase in its electrical resistance. This detrimentally impacts the electrical performance of the integrated circuit.2 Furthermore, aggressive interconnect size scaling below the 10 nm node poses challenges to void-free interconnect fabrication. State-of-the-art interconnects are fabricated of Cu metal due to its low electrical resistivity and superior electromigration resistance.3 The interconnect signal delay (τ) is given by τ = RC, where R is the interconnect resistance and C is the capacitance of the surrounding inter-layer dielectric. The interconnect resistance R increases dramatically for Cu interconnect dimensions below 40 nm due to the substantial increase in the electrical resistivity of Cu at such narrow dimensions. The resistivity increase is typically attributed to electron scattering processes at grain boundaries and at interfaces within the Cu interconnect structure. Such scattering processes become dominant when the interconnect dimension approaches the electron mean free path (EMFP = 39 nm at room temperature) in Cu.4,5 As a consequence, the interconnect signal delay increases. To overcome this critical issue, an interconnect material which exhibits lower electrical resistivity at narrow (sub 10 nm) dimensions is required. Cobalt (Co) is considered as a promising alternative interconnect material to replace the conventionally used Cu.6,7 At narrow dimensions, i.e., below 10 nm, Co exhibits comparable or lower electrical resistivity compared to Cu, largely attributed to the lower ...

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Hot-wire-assisted atomic layer deposition of a high quality cobalt film using cobaltocene: Elementary reaction analysis on NHx radical formation

Cited by 49 publications

References 38 publications

Hot-Wire Generated Atomic Hydrogen and its Impact on Thermal ALD in TiCl₄/NH₃System

Hot-Wire Generated Atomic Hydrogen and its Impact on Thermal ALD in TiCl₄/NH₃System

Hot-wire assisted ALD of tungsten films:In-situstudy of the interplay between CVD, etching, and ALD modes

Electrochemical Atomic Layer Deposition of Cobalt Enabled by the Surface-Limited Redox Replacement of Underpotentially Deposited Zinc

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Hot-wire-assisted atomic layer deposition of a high quality cobalt film using cobaltocene: Elementary reaction analysis on NHx radical formation

Cited by 49 publications

References 38 publications

Hot-Wire Generated Atomic Hydrogen and its Impact on Thermal ALD in TiCl4/NH3System

Hot-Wire Generated Atomic Hydrogen and its Impact on Thermal ALD in TiCl4/NH3System

Hot-wire assisted ALD of tungsten films:In-situstudy of the interplay between CVD, etching, and ALD modes

Electrochemical Atomic Layer Deposition of Cobalt Enabled by the Surface-Limited Redox Replacement of Underpotentially Deposited Zinc

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Hot-Wire Generated Atomic Hydrogen and its Impact on Thermal ALD in TiCl₄/NH₃System

Hot-Wire Generated Atomic Hydrogen and its Impact on Thermal ALD in TiCl₄/NH₃System