Low temperature transport of Al into and through copper starting with Cu/Al/SiO2 bilayers

Lanford, W. A.; Bedell, Stephen W.; Isberg, P.; Hjörvarsson, Bjørgvin; Lakshmanan, Satish K.; Gill, William N.

doi:10.1063/1.369336

Cited by 7 publications

(3 citation statements)

References 16 publications

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“…Since the activation energy for diffusion along extended defects tends to scale with the melting point of the material, 6 copper diffusion barriers currently under investi-a͒ Author to whom correspondence should be addressed; electronic mail: plawsky@rpi.edu gation include refractory metals and their compounds TiW, TiN, TiN x , TiSi 2 , Ta, TaN, Ta 2 N, W, WN, W 2 N, WN x , 7 and Al. 8 Currently it appears that Ta based barriers are most likely to be used. It has been reported 9 that as-deposited copper adheres well to SiO 2 , but after annealing at temperatures above 200°C, the copper occasionally lifts from the substrate, indicating thermal stress related adhesion failures.…”

Section: Introductionmentioning

confidence: 99%

Interactions between silica xerogel and tantalum

Rogojevic

Jain

Wang

et al. 2001

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Investigation of the interfacial reaction between metal and fluorine-contained polyimides J. Vac. Sci. Technol. A 23, 862 (2005); 10.1116/1.1868632 Failure mechanism of Ta diffusion barrier between Cu and SiThin films of tantalum, a potential diffusion barrier, were deposited on xerogel films. The structures were annealed at different temperatures and in different ambient environments and analyzed using Rutherford backscattering spectrometry ͑RBS͒, optical microscopy, and the Scotch™ tape test, in order to assess the extent of interaction with the xerogel film. When annealed in nitrogen with at most trace amounts of oxygen ͑equivalent to 10 Ϫ7 -10 Ϫ6 Torr vacuum͒, RBS analysis for Ta does not show diffusion of this metal through the xerogel when annealed up to 450°C. However, the presence of larger concentrations of oxygen in the annealing environment was found to cause oxidation of Ta thin films, and this leads to Ta film buckling and diffusion-like RBS spectra. Ta does not buckle nor diffuse into the xerogel film at temperatures up to 640°C when the metal is capped with a Si 3 N 4 layer. Analysis of the samples by RBS microbeam shows that the low energy Ta tail originates from only a portion of the sample surface, the shape of which resembles Ta buckles. RBS spectra collected from other parts of the samples show no Ta diffusion into xerogel. Adhesion of Ta to porous xerogel is reduced compared to SiO 2 , due to the reduced contact area at the interface between the materials.

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Section: Introductionmentioning

confidence: 99%

Interactions between silica xerogel and tantalum

Rogojevic

Jain

Wang

et al. 2001

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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“…The layer behaves as an effective diffusion barrier to protect the underlying Cu and Ta layers. 15,16 The formation of Al 2 O 3 is thermodynamically favorable compared to Cu oxide due to the large difference in oxide formation energy between Al ͑−226 kcal/g mol …”

Section: Resultsmentioning

confidence: 99%

High-Reliability Ta[sub 2]O[sub 5] Metal–Insulator–Metal Capacitors with Cu-Based Electrodes

Tsai

Chao

et al. 2006

J. Electrochem. Soc.

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The properties of tantalum oxide ͑Ta 2 O 5 ͒ metal-insulator-metal ͑MIM͒ capacitors with Al/Ta/Cu/Ta bottom electrodes were investigated. An ultrathin Al film successfully suppresses oxygen diffusion in the Ta 2 O 5 MIM capacitor with the Cu-based electrode. The electrical characteristics and reliability of Ta 2 O 5 MIM capacitors are improved by addition of ultrathin Al films. Ta 2 O 5 MIM capacitors have low leakage current density ͑1 nA/cm 2 at 1 MV/cm͒ and high breakdown field ͑5.2 MV/cm at 10 −6 A/cm 2 ͒. The decrease in leakage current is attributed to the formation of a dense and uniform Al 2 O 3 layer, which has self-protection property and stops further oxygen diffusion into the tantalum contact. The dominant conduction mechanism of leakage current is the Poole-Frenkel effect at electric fields above 1.5 MV/cm. Metal-insulator-metal ͑MIM͒ capacitors are used as radio frequency ͑rf͒ capacitors in high-frequency circuits and analog capacitors in mixed-signal integrated circuit ͑IC͒ applications due to their high conductive electrodes and low parasitic capacitance. 1-3 As the circuit density increases, materials with a dielectric constant ͑͒ much higher than SiO 2 ͑ϳ3.9͒ are desired. 4 Among various highdielectric candidates, tantalum pentoxide ͑Ta 2 O 5 ͒ has been studied as a promising material for a gate dielectric of metal-oxide semiconductor field effect transistors because of its high dielectric constant and excellent thermal and chemical stability. 5,6 Current semiconductor technology demands the use of lowresistivity metals as electrode materials for ultralarge-scale integrated ͑ULSI͒ conduction lines and contact structures. In order to minimize the cost of ownership aspect in the electrode processes, several metallization technologies have been proposed in IC applications. Platinum ͑Pt͒ and ruthenium ͑Ru͒ have been used as the electrodes of capacitors with high-dielectric materials. 7,8 Pt and Ru, however, have limitations for application due to their high resistivity ͑Pt: ϳ 10.6 ⍀ cm, Ru: ϳ 7.7 ⍀ cm͒, cost, and leakage current. 9 Cu-based metallization technology could be incorporated into devices owing to ease of processing and reduction in production cost of silicon rf capacitors and mixed-signal ICs. In addition, Cu has low resistivity ͑1.67 ⍀ cm͒ and high electro-and stress-migration resistance. However, Cu oxidizes during the initial stage of Ta 2 O 5 reactive sputtering, and hillocks or particles are observed after annealing in oxygen ambient. 10,11 Significant efforts have been made to identify an appropriate diffusion barrier layer for Cu-based electrodes. Among these diffusion barrier materials, tantalum ͑Ta͒ is selected for Cu-based electrodes because it not only has low resistivity but also is thermodynamically stable with Cu. 12,13 Unfortunately, the grain boundaries of a sputtered Ta layer generally provide paths for oxygen and copper diffusion when formation of Ta 2 O 5 dielectrics requires processing under high temperature and oxygen ambient. Protection against oxidation and copper ...

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“…3,4 Current technology uses silicon dioxide (SiO 2 ) as an interlayer dielectric material ͑ILD͒ to insulate copper lines and vias since SiO 2 is a stable material with well-developed CMP slurries and process conditions. 5 Challenges in copper damascene patterning emerge with thinner barriers 6 and alternative dielectric materials that may be softer and more difficult to polish. A scaled damascene CMP process is desired that will polish through a thin or nonexistent copper diffusion barrier and directly abrade and remove a low-material.…”

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confidence: 99%

Surface Kinetics Model for SiLK Chemical Mechanical Polishing

Borst

Thakurta

Gill

et al. 2002

J. Electrochem. Soc.

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The surface mechanism for SiLK removal by chemical mechanical polishing ͑CMP͒ is modeled quantitatively using modified Langmuir-Hinshelwood surface reaction kinetics to define the boundary condition on the wafer surface for three-dimensional diffusive mass-transport equations. The model generates slurry concentration distributions between the pad and wafer as well as a CMP removal rate profile along the wafer diameter. Mathematically predicted removal rates of 15-200 nm/min accurately represent experimental data for concentrations of 0.0015-0.024 M potassium-hydrogen phthalate slurry. Three-dimensional model fits to experimental data for a range of velocity and pressure indicate that the SiLK CMP removal rate is controlled by a combination of ͑i͒ chemical reaction altering the SiLK surface layer and ͑ii͒ physically enhanced desorption of the reacted surface layer into the surrounding slurry.

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Low temperature transport of Al into and through copper starting with Cu/Al/SiO2 bilayers

Cited by 7 publications

References 16 publications

Interactions between silica xerogel and tantalum

Interactions between silica xerogel and tantalum

High-Reliability Ta[sub 2]O[sub 5] Metal–Insulator–Metal Capacitors with Cu-Based Electrodes

Surface Kinetics Model for SiLK Chemical Mechanical Polishing

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