Electroless Deposition of Cu Thin Films with CuCl[sub 2]-HNO[sub 3] Based Chemistry: I. Chemical Formulation and Reaction Mechanisms

Tseng, Wei–Tsu; Lo, Chia-Hsien; Lee, Shih-Chin

doi:10.1149/1.1359200

Cited by 28 publications

(26 citation statements)

References 9 publications

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“…2 A brief description is presented here. 100 mm p-type ͑1.7-2.5 ⍀ cm resistivity͒ ͗100͘ Si wafers are thermally oxidized in dry atmosphere to produce an oxide thickness of 100 nm.…”

Section: Methodsmentioning

confidence: 99%

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Electroless Deposition of Cu Thin Films with CuCl[sub 2]-HNO[sub 3] Based Chemistry: II. Kinetics and Microstructure

Tseng

Lee

2001

J. Electrochem. Soc.

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This paper describes the kinetics involved in the acid-based electroless Cu deposition system employing CuCl 2 -HNO 3 chemistry in a HF-NH 4 F buffer solution. The rate equation is set up as a function of concentrations of active chemical components involved, and rate orders are determined to evaluate the contribution from each component. The deposition rate of Cu is found most sensitive to variation in ͓Cl Ϫ ͔ concentrations, followed by that of ͓Cu 2ϩ ͔ and ͓F Ϫ ͔. The activation energy derived from deposition at different temperatures is 0.445 eV. Grain size of deposited Cu films is influenced strongly by deposition rate. Electrical resistivity of Cu films is dominated by the amount of point defects and microvoids present right after deposition, and by grain size after a 300°C anneal.Electroless plating provides a viable alternative to electroplating for Cu thin-film deposition in the era of Cu-based multilevel interconnect for microelectronic devices. 1 Besides its capability of filling high-aspect-ratio pattern structure, electroless plating offers additional advantages such as low cost and simpler chemistry.Most existing electroless Cu plating processes adopt base solutions with copper sulfate as the Cu ion source, ethylenedinitroloacetate ͑EDTA͒ as the complexing agent, formaldehyde as reducing agents, tetramethylammonium hydroxide ͑TMAH͒ or alkali solution as pH buffer, and some surfactant and stabilizer added to improve step coverage and bath stability, respectively. This chemical formulation has been studied extensively over the past twenty years and has been applied to the manufacture of circuit boards.In the first part of this study, 2 we proposed an acid-based CuCl 2 -HNO 3 electroless Cu plating solution with HF-NH 4 F as pH buffer. An optimum deposition rate of ϳ2700 Å/min directly on TaN substrate and a resistivity of 2.35 ⍀ cm can be achieved at pH 4.70. CuCl 2 , when dissolved in the solution, provides the ͓Cu 2ϩ ͔ ions, which are catalyzed by HNO 3 on TaN surface and reduced by Si to form Cu deposits. ͓Cl Ϫ ͔ and ͓F Ϫ ͔ ions act as complexing agents and transmit the electrons from Si to ͓Cu 2ϩ ͔. Cu deposition rate exhibits a decreasing trend with increasing ͓HNO 3 ͔ concentration in the bath. Adding ͓HF͔ or ͓NH 4 F͔ into the bath, on the other hand, enhances the deposition rate to a peak level, after which it saturates and declines.As an extension of our previous study, we explore the kinetics and material issues of the system in this contribution. Concentration of the active components and temperature used in the system are varied in order to deduce the reaction rate orders and activation energy. Evolution of grain size and resistivity with ͓Cu 2ϩ ͔ concentration in the chemical bath are analyzed. The effects of postdeposition anneal on resistivity, microstructure, and preferred crystal orientation of Cu thin films are also investigated. ExperimentalDetermination of reaction rates.-Chemical components and substrate materials used for the Cu deposition experiment basically follow those from ou...

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“…2 A brief description is presented here. 100 mm p-type ͑1.7-2.5 ⍀ cm resistivity͒ ͗100͘ Si wafers are thermally oxidized in dry atmosphere to produce an oxide thickness of 100 nm.…”

Section: Methodsmentioning

confidence: 99%

“…Resistivity of Cu was determined from a correlation curve between sheet resistance and thickness ͑from SEM͒, as used previously. 2 After deposition, X-ray diffractometer ͑XRD͒ measurements are performed to analyze the preferred crystal orientation of Cu films. The XRD plots are derived from 2-coupled geometry employing a Cu anode at 45 kV and 30 mA.…”

mentioning

confidence: 99%

Electroless Deposition of Cu Thin Films with CuCl[sub 2]-HNO[sub 3] Based Chemistry: II. Kinetics and Microstructure

Tseng

Lee

2001

J. Electrochem. Soc.

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“…The scotch tape test is usually employed to evaluate adhesion of the films on the substrates [31], and it was repeated three times on each specimen. Those without any visible Ni-Mo-P damage after tests are classified as excellent, and those with some spots left on the film after tests are defined as good, and those which peeled off easily are decided as poor [32][33]. In this paper, the adhesion tests were performed by the Cu/Ni-Mo-P/SiO 2 /Si and Ni-Mo-P/SiO 2 /Si specimens.…”

Section: Adhesion Of As-deposited Ni-mo-p Alloys To the Substratementioning

confidence: 99%

Electroless Ni–Mo–P diffusion barriers with Pd-activated self-assembled monolayer on SiO2

Liu

Yang

Zhang

2010

Materials Science and Engineering: B

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“…The simplest and potentially lowest cost metallization process is the "fully additive" process where electroless plating is used to build the full thickness of the metal layer [33]. Electroless plating is a low cost and batch processing technique suited for high-volume manufacturing.…”

Section: ) New Conductor Metallization Processesmentioning

confidence: 99%

Next-Generation Microvia and Global Wiring Technologies for SOP

Sundaram

Tummala

Liu

et al. 2004

IEEE Trans. Adv. Packag.

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As microsystems continue to move toward higher speed and microminiaturization, the demand for interconnection density both on the IC and the package levels increases tremendously. The 2002 ITRS roadmap update identifies the need for sub-100-m area array pitch and data rates of 10 Gb/s in the package or board by the year 2010, requiring much finer lines and vias than the current microvias of 50 m diameter and lines and spaces of 25 m. After a brief description of the future need for high-density substrates, the historical evolution of microvia technologies worldwide is summarized. With the move toward highly integrated and higher performance system-on-a-package (SOP) technology, the demand for microvia wiring density in the package is increasing dramatically requiring new innovations in fine line, ultralow-loss, and ultrathin-film dielectrics. The low-cost needs of this technology are driving research in high throughput and large area processes in dielectric and conductor deposition. The third section of this paper describes in detail some of the key emerging global microvia research and development in the fabrication of microminiaturized, multifunction SOP packages including rapid curing of low-loss dielectric thin films on organic substrates, environmentally friendly high-speed electroless copper plating, ultrafine lines, and spaces down to 5 m and low-cost stacked via structures without chemical-mechanical polishing. This paper concludes with a perspective on future directions in dielectrics and conductor materials and processes leading to ultrahigh-density and low-cost microvia technologies for build-up SOP implementation.Index Terms-Conductors, embedded passives, fine lines, global interconnect, high speed, low-loss dielectrics, microvia, PWB, stacked vias, system-in-a-package (SIP), system-on-a-package (SOP), thin film.

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Electroless Deposition of Cu Thin Films with CuCl[sub 2]-HNO[sub 3] Based Chemistry: I. Chemical Formulation and Reaction Mechanisms

Cited by 28 publications

References 9 publications

Electroless Deposition of Cu Thin Films with CuCl[sub 2]-HNO[sub 3] Based Chemistry: II. Kinetics and Microstructure

Electroless Deposition of Cu Thin Films with CuCl[sub 2]-HNO[sub 3] Based Chemistry: II. Kinetics and Microstructure

Electroless Ni–Mo–P diffusion barriers with Pd-activated self-assembled monolayer on SiO2

Next-Generation Microvia and Global Wiring Technologies for SOP

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