Effects of Ru-Ta Alloy Barrier on Cu Filling and Reliability for Cu Interconnects

Mori, Kohsuke; Ohmori, Kazuyuki; Torazawa, Naoki; Hirao, S.; Kaneyama, Syutetsu; Korogi, Hayato; Maekawa, Kazuyoshi; Fukui, Shoichi; Tomita, Kazuo; Inoue, Makoto; Chibahara, Hiroyuki; Imai, Yuki; Suzumura, N.; Asai, Koyu; Kojima, Masayasu

doi:10.1109/iitc.2008.4546937

Cited by 11 publications

(11 citation statements)

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“…Among all of the copper adhesion/barrier alternative materials, Ru has generated the most interest and has been intensively studied. [1][2][3][4] However, toxic and volatile RuO 4 is likely to form in the acid slurry during the CMP Ru process. 5 Compared with Ru(ρ bulk Ru = 7.1 μ · cm), Co(ρ bulk Co = 6.3 μ · cm) is much cheaper with lower electrical resistivity, and also has similar barrier and adhesion properties as Ru.…”

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confidence: 99%

The Effect of H2O2 and 2-MT on the Chemical Mechanical Polishing of Cobalt Adhesion Layer in Acid Slurry

Wang

et al. 2012

Electrochem. Solid-State Lett.

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Cobalt has emerged as a potential adhesion layer for advanced copper metallization. This work investigates the role of oxidant and inhibitor on the corrosion and polishing properties of cobalt in the acid slurry. It is found that H 2 O 2 could greatly increase the static etch rate (SER) and removal rate (RR) of cobalt. The 2-Mercaptothiazoline (2-MT) is very efficient to inhibit cobalt corrosion and reduce the SER and RR of cobalt in the acid slurry. In the glycine based slurry at pH = 5, by using 2-MT, the corrosion potential difference between Co and Cu can be reduced to a very small value.

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confidence: 99%

The Effect of H2O2 and 2-MT on the Chemical Mechanical Polishing of Cobalt Adhesion Layer in Acid Slurry

Wang

et al. 2012

Electrochem. Solid-State Lett.

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“…with low resistivity have been proposed to replace Ta as Cu adhesion layer because of the ability of direct ECD of Cu on their surface, which is beneficial for conformal ECD Cu gap filling. [16][17][18] Ru is considered as one of the most promising material as Cu adhesion layer in the future technology node. 17,19,21,22 It is reported that the predicted circuitperformance using the Ru based barrier was 10% higher than that with a Ta barrier and the operating-speed distribution was estimated to be less than 5% for the 22 nm-node CMOS generation.…”

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confidence: 99%

The Inhibition of Enhanced Cu Oxidation on Ruthenium∕Diffusion Barrier Layers for Cu Interconnects by Carbon Alloying into Ru

Xie

Müeller

Waechtler

et al. 2011

J. Electrochem. Soc.

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The inhibition of Cu oxidation by alloying C into the Ru/TaN barrier stack is investigated. By using in-situ XRD measurement, severe copper oxide formation was observed for the Cu/Ru/barrier system during annealing process in He atmosphere. This phenomenon is explained using thermodynamics from the viewpoint of Gibbs free energy of oxide formation. The Cu oxidation can be inhibited by alloying C into the Ru layer, and the more C content in the RuC layer, the more evident the inhibition effect. The RuC/TaN stack also shows better diffusion barrier properties than the Ru/TaN bi-layer. Atomic layer deposition of Cu 2 O on the RuC substrate was carried out and reduction of the Cu 2 O to Cu was observed. The mechanism of inhibition of Cu oxidation on C alloyed Ru was investigated by a first principles calculation based on the density functional theory.As the interconnect line width continually scales down, the reliability problem induced by stress induced voiding (SiV) and electromigration (EM) becomes severe. 1-6 The SiV and EM problem are mainly caused by poor adhesion between Cu and the glue layer or capping layer. 1, 6-11 It is found that the oxidation of Cu or barrier layer will degrade the adhesion between Cu and the glue layer, 1, 12-14 resulting in delamination during chemical mechanical polishing (CMP) and reliability problems. Cu oxidation Cu can also increase the line resistance and thus increase the RC delay and degrade the performance of the devices. During the back end of line (BEOL) manufacturing process, Cu oxidation is easily observed because of many thermal processes and the unavoidable oxygen processes such as electrochemical deposition (ECD) of Cu. In order to inhibit Cu oxidation and improve the reliability of Cu interconnects, many methods have been proposed, such as using Ti instead of Ta as the Cu adhesion layer, 9 or adding an oxygen adsorption layer, such as Al 1 or Ti 15 on the pure ECD-Cu film before annealing.Recently, novel materials such as Ru 16,17,19 and Co 16, 20 etc. with low resistivity have been proposed to replace Ta as Cu adhesion layer because of the ability of direct ECD of Cu on their surface, which is beneficial for conformal ECD Cu gap filling. [16][17][18] Ru is considered as one of the most promising material as Cu adhesion layer in the future technology node. 17,19,21,22 It is reported that the predicted circuitperformance using the Ru based barrier was 10% higher than that with a Ta barrier and the operating-speed distribution was estimated to be less than 5% for the 22 nm-node CMOS generation. 19 However, there are still some concerns such as severe oxidation of copper and galvanic corrosion during the CMP process. 16 In this work, the effect of Ru on enhanced Cu oxidation was studied and by adding C into Ru, the inhibition of Cu oxidation and promotion of Cu 2 O reduction were studied.Experimental P-type Si (100) substrates were loaded into the vacuum chamber through a loadlock after standard chemical cleaning. The base pressure of the vacuum was 2 × 10 −7 mbar. TaCN a...

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“…1) Low resistivity and strong Cu/barrier adhesion ability are two important factors in choosing a material for a good Cu glue layer. Nowadays, there are a variety of novel metal materials with low resistivities, including Ru, 1,[7][8][9][10][11] Co, 12) Pd, 13) Rh, 14) Mo, 15) Os, 1) and Ir, 16,17) which have been identified as possible candidate materials for Cu glue layers. Kim and coworkers performed a systematic evaluation of the Cu adhesion property on different glue layers, such as Ta, Ru, Mo, and Os, and their experimental results show that a glue layer material with a low lattice misfit to Cu has a promising Cu adhesion property.…”

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confidence: 99%

Density Functional Theory Study of Cu Adhesion on Rh, Ir, Pd, Ta, Mo, Ru, Co, and Os Surfaces

Chen

Jiang

et al. 2011

Jpn. J. Appl. Phys.

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In this work, first-principles calculation based on the density functional theory was applied to study Cu adhesion on the surfaces of Rh(111), Ir(111), Pd(111), Ta(110), Mo(110), Co(0001), Os(0001), and Ru(0001), on which the adsorption energy, electron density difference, and geometrical structures of Cu were investigated. The analysis of the calculated and experimental results shows that the atomic chemical interaction, surface lattice mismatch, and crystal lattice type have marked effects on Cu adhesion on glue layers. Cu atoms on all the metal surfaces studied in this work are more likely to form the fcc structure with a quasi-(111) orientation. The coupling effect of the large surface lattice mismatch and the lattice type difference between Cu and the metal surface can greatly reduce Cu adhesion ability. Among all the studied metals, Ir and Os showed comparable adhesion ability to Ru and can be considered as promising Cu glue layers for Cu interconnects.

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Effects of Ru-Ta Alloy Barrier on Cu Filling and Reliability for Cu Interconnects

Cited by 11 publications

References 0 publications

The Effect of H2O2 and 2-MT on the Chemical Mechanical Polishing of Cobalt Adhesion Layer in Acid Slurry

The Effect of H2O2 and 2-MT on the Chemical Mechanical Polishing of Cobalt Adhesion Layer in Acid Slurry

The Inhibition of Enhanced Cu Oxidation on Ruthenium∕Diffusion Barrier Layers for Cu Interconnects by Carbon Alloying into Ru

Density Functional Theory Study of Cu Adhesion on Rh, Ir, Pd, Ta, Mo, Ru, Co, and Os Surfaces

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