Cobalt bottom-up contact and via prefill enabling advanced logic and DRAM technologies

Veen, Marleen H. van der; Vandersmissen, K.; Dictus, Dries; Demuynck, S.; Liu, R.; Xue, Bin; Nalla, Praveen; Leśniewska, A.; Hall, L.; Croes, Kristof; Zhao, Larry; Bömmels, J.; Kolics, A.; Tőkei, Zs.

doi:10.1109/iitc-mam.2015.7325605

Cited by 44 publications

(24 citation statements)

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“…The absorption spectra of the supernatants collected from the same dispersions, but now at pH 2, are shown in Figure 8. A spectral peak was observed at ∼517 nm which corresponds to the water soluble complex [Co(H 2 O) 6 ] 2+ as reported by several authors. [55][56][57] This indicates that not only temperature but also addition of H + ions enhances the dissolution rates of Co, consistent with Reaction 1 and Figure 1.…”

Section: Resultssupporting

confidence: 48%

“…Cobalt is a promising alternative to meet the challenges of interconnect lines at these lower nodes for the first two metal layers M1 and M2, due to its lower resistivity at smaller dimensions (∼10 nm) compared to copper. [4][5][6] Kamineni et al 7 proposed the use of chemical vapor deposited (CVD) cobalt to replace the widely used tungsten for local interconnects for 10 nm and smaller nodes. They emphasized two main advantages of CVD Co metallization which are a) CVD Co precursors do not damage the Ti liner enabling barrier scaling and b) it achieves void free fill in high aspect ratio features without defects, something that is difficult to achieve with a conventional physical vapor deposited (PVD) Co process.…”

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confidence: 99%

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Citric Acid as a Complexing Agent in Chemical Mechanical Polishing Slurries for Cobalt Films for Interconnect Applications

Popuri

Sagi

Alety

et al. 2017

ECS J. Solid State Sci. Technol.

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A colloidal silica-based slurry (3-10 wt%) containing H 2 O 2 (1 wt%) and citric acid (50 mM) was found to polish chemical vapordeposited (CVD) cobalt (Co) films with removal rates (RRs) of ∼180-500 nm/min and a dissolution rate (DR) of ∼0 nm/min at pH 8 along with an RMS roughness of ∼0.5 nm and a corrosion current of ∼50 μA/cm 2 . Our results suggest that, in the presence of H 2 O 2 , the Co film surface was covered with a passive film of CoO in acidic conditions and Co 3 O 4 in alkaline conditions. However, in the presence of H 2 O 2 and citric acid in acidic conditions, formation of the soluble complex [Co(C 6 H 5 O 7 ) 2 ] 3− from abraded Co enhanced the RRs significantly. The roles of H 2 O 2 , citric acid, and silica abrasives as well as the pH on the Co material removal process are discussed and a removal mechanism is proposed. Two inhibitors namely, 1, 2, 4-Triazole (TAZ) and Benzotriazole (BTA), were tested in the presence of 50 mM citric acid at pH 8 but were found to be ineffective even at concentrations of 100 mM in reducing the E corr of Co-Ti couple to minimize galvanic corrosion that is essential when the Co/Ti structure is polished after the removal of bulk of Co and requires further study. Sub-10 nm devices face several challenges with copper as an interconnect material for back-end-of-the-line (BEOL) processes during the manufacture of integrated circuits. These include increasing resistivity with decreasing thickness, 1 non-conformal deposition at narrow trench widths ∼20 nm or less, 2 and scaling limitations of the diffusion barrier/liner.3 This led to the investigation of new trench filling materials. Cobalt is a promising alternative to meet the challenges of interconnect lines at these lower nodes for the first two metal layers M1 and M2, due to its lower resistivity at smaller dimensions (∼10 nm) compared to copper. [4][5][6] Kamineni et al. 7 proposed the use of chemical vapor deposited (CVD) cobalt to replace the widely used tungsten for local interconnects for 10 nm and smaller nodes. They emphasized two main advantages of CVD Co metallization which are a) CVD Co precursors do not damage the Ti liner enabling barrier scaling and b) it achieves void free fill in high aspect ratio features without defects, something that is difficult to achieve with a conventional physical vapor deposited (PVD) Co process. 8,9 Hence, CVD-based Co metallization is an attractive option for the technology nodes below 10 nm.CVD-based cobalt has also gained prominence in the advanced copper interconnects below 22 nm as liner [10][11][12][13][14][15][16][17] to improve adhesion between the barrier (TaN, TiN) and Cu seed layer where the Co film thickness is only ∼2 nm. Several authors 18-26 have investigated cobalt polishing for such applications where RR requirements are typically <20 nm/min and Co loss due to corrosion has to be as close to zero as possible, since even a minute loss of Co material can degrade the device reliability significantly. Hence, since the potential gap between Co and Cu is a large ∼0...

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Section: Resultssupporting

confidence: 48%

mentioning

confidence: 99%

Citric Acid as a Complexing Agent in Chemical Mechanical Polishing Slurries for Cobalt Films for Interconnect Applications

Popuri

Sagi

Alety

et al. 2017

ECS J. Solid State Sci. Technol.

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“…Thinner barrier and adhesion layers, doping of metals to enhance the grain boundary conductance, and selective capping are some of the adopted solutions improving copper interconnects. Other short-term solutions to address the scaling challenges faced by Cu include load-aware redundant double vias to avoid EM issues [6], via prefill with alternate materials (like Cobalt) with higher current migration resistance and better fill [7], ultra-thin self-forming barriers (metal oxide barriers like MnO x ) to optimize the utilizable cross-section for Cu, alternative materials for better EM [8], reflow seed layers for defect reduction [9], etc. Nevertheless, these short-term steps aim to solve one or few of the Cu-foreseen issues at once and to combine them might prove to be impractical or just economically unfeasible.…”

Section: Introductionmentioning

confidence: 99%

A Survey of Carbon Nanotube Interconnects for Energy Efficient Integrated Circuits

Todri‐Sanial

Ramos

Okuno

et al. 2017

IEEE Circuits Syst. Mag.

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“…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 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.…”

mentioning

confidence: 99%

“…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. Electroless Co deposition too has drawbacks such as the use of toxic reductants, e.g., formaldehyde or hydrazine.…”

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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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Cobalt bottom-up contact and via prefill enabling advanced logic and DRAM technologies

Cited by 44 publications

References 1 publication

Citric Acid as a Complexing Agent in Chemical Mechanical Polishing Slurries for Cobalt Films for Interconnect Applications

Citric Acid as a Complexing Agent in Chemical Mechanical Polishing Slurries for Cobalt Films for Interconnect Applications

A Survey of Carbon Nanotube Interconnects for Energy Efficient Integrated Circuits

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

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