New plating bath for electroless copper deposition on sputtered barrier layers

Lantasov, Yuri; Palmans, Roger; Maex, Karen

doi:10.1016/s0167-9317(99)00313-5

Cited by 47 publications

(34 citation statements)

References 2 publications

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“…15 Gap-filling capability of electroless Cu deposition.-One of the most important advantages of using electroless Cu deposition is the good step coverage and gap-filling ability. [5][6][7] In order to examine the feasibility of Sn/Pd catalyzation and electroless Cu deposition for the metallization of ULSI devices, patterned TaN/SiO 2 /Si substrates were also catalyzed and electrolessly Cu deposited using the same solutions. Figure 11 shows the SEM morphologies of cleaved cross sections of trenches and vias filled by electroless Cu.…”

Section: Smooth Deposition Reveals a Complete Connection Of The Cu Grmentioning

confidence: 99%

Sn/Pd Catalyzation and Electroless Cu Deposition on TaN Diffusion Barrier Layers

Hsu

Teng

Lin

et al. 2002

J. Electrochem. Soc.

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The catalyzation of TaN/SiO 2 /Si substrates was carried out by immersion in SnCl 2 /HCl and PdCl 2 /HCl solutions for electroless Cu deposition. The sizes and morphologies of the catalytic sites on the TaN layers were found to be a function of catalyzation conditions, including solution temperature, immersion time, and the surface oxides. The appropriate formula for catalyzation was obtained by considering both the quality and efficiency. The catalytic sites were composed of Sn and Pd, and the ratio of Sn/Pd was about 1.3. During electroless Cu deposition on the catalyzed TaN/SiO 2 /Si substrates, Cu nuclei first formed at the catalytic sites in the early stage, gradually agglomerated into dense islands, and finally merged to continuous deposition films. The Cu films were uniformly and smoothly deposited with a surface roughness of 6.2 nm under a film thickness of 210 nm. The lowest electrical resistivity of the Cu films was 2.5 ⍀ cm, and the residual resistivity contributed to the participation of Sn-Pd catalyst and internal defects. Good gap-filling capability of electroless Cu deposition on Sn/Pd catalyzed, patterned substrates exhibited its high potential to act as a seed layer for Cu electrodeposition and even to completely fill submicrometer gaps in ultralarge-scale integrated metallization.Metallization is a critical issue in the production of ultralargescale integrated ͑ULSI͒ circuits. As the size of the devices scales down and chip density highly increases, copper ͑Cu͒ has been proposed as the most reliable interconnect material to replace aluminum because of its significant advantages of low electrical resistivity, low power dissipation, and high resistance to electromigration. 1,2 Recently, Cu deposition by electrochemical methods has received great attention, since high-quality Cu films can be easily obtained at a low deposition temperature and by low tool cost. 3,4 Electroless copper deposition has excellent step-coverage capability for high-aspectratio ͑A.R.͒ gaps and can be used either to produce the seed layer for copper electrodeposition or to fill the fine gaps directly. 5-7 Besides, due to the high selectivity, the low processing temperatures, the low cost of raw materials and equipment, and the feasibility, 8 it becomes attractive and is under continuous investigation.However, some problems associated with Cu metallization must be solved, especially, the easy diffusion of Cu into SiO 2 and Si and its poor adhesion to dielectric layers. Therefore, for the successful integration of Cu metallization with integrated circuit ͑IC͒ processes, proper diffusion barrier layers of refractory metals and their nitrides are required to be placed between Cu and either the dielectric layers or the Si substrate to prevent the diffusion of Cu and to improve interfacial adhesion. Tantalum nitride ͑TaN͒, recognized as one of the most promising diffusion barriers for Cu, not only provides high thermal stability, but also has characteristics such as acceptable conductivity and the chemical inactivity with Cu. 9,10...

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Section: Smooth Deposition Reveals a Complete Connection Of The Cu Grmentioning

confidence: 99%

Sn/Pd Catalyzation and Electroless Cu Deposition on TaN Diffusion Barrier Layers

Hsu

Teng

Lin

et al. 2002

J. Electrochem. Soc.

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“…The intensity of the ͗111͘-textured Cu was much higher than that oriented in the ͗200͘ direction. Since it has been suggested that ͗111͘-textured Cu is better able to resist electronmigration, 11 we believe that our displacement copper lines should behave reliably.…”

Section: Resultsmentioning

confidence: 63%

Selective Deposition of Cu Interconnects by Prepatterned Ta Film

Yang¹,

Yang

Chang

et al. 2006

J. Electrochem. Soc.

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A process of fabricating Cu layers by displacement reaction is demonstrated in this study. A prepatterned Ta film on a TaN layer was displaced by a redox reaction to form the copper top layer. The TaN layer was included to improve adhesion between the copper and the dielectric layers. The average electrical resistivity obtained from the Cu films was 2.02 ⍀ cm after thermal annealing. Reliability analysis showed that the activation energy of the copper interconnect was 0.94 eV, which was close to the result for Cu films grown by sputtering.For future ultralarge-scale integration, the ever-decreasing lateral dimensions of contacts and holes require new developments in metallization technology. Consequently, copper has been studied as an alternative metal for interconnections due to its lower resistivity, better mechanical properties, and electromigration resistance compared to aluminum. 1,2 For Cu metallization, an efficient diffusion barrier is required to prevent Cu atoms from penetrating into dielectrics or Si substrates. Since copper is highly diffusive and drifts into the surrounding dielectric layer even at low temperatures, 3,4 a highly conducting diffusion/drift barrier typically less than 20 nm thick is needed to separate the Cu from the dielectric layer. Refractory metals and their nitrides have been used and thoroughly investigated for interconnection applications. These materials are promising as diffusion barriers because of their good thermal stability at elevated temperatures. 5 Several methods have been proposed for depositing Cu on these diffusion barriers, e.g., physical vapor deposition, 6,7 chemical vapor deposition, 8,9 and electrochemical deposition ͑ECD͒. 10,11 However, since the substrate surface is generally not catalytic, a seeding treatment or surface modification must be invoked to initiate the deposition of an electroless barrier for Cu. Traditionally, predeposition of a catalyst is carried out by sensitizing and activating the surface in tin-palladium colloidal solutions or tin-free PdCl 2 acidic solutions, or by UV-induced copolymer-grafting molecular modification, thereby forming disjointed catalytic sites on the surface to be metallized. 12 Recently, a simple and fast displacement technique for Cu metallization has been proposed. It involves forming a seed layer of copper directly by displacement of Ta in the barrier layer. This technique is attractive in the microelectronics and semiconductor industries because of its low processing temperature, high step coverage, high selectivity, low cost, and no need for sensitization and activation. 13 Although direct electroless copper plating onto TiN, TaN, and WN does not require catalysis adsorption pretreatment, it is necessary to prepare complex solutions containing diamine-tetraacetic, glyoxylic acid as a reducing agent, polyethylene glycol as a surfactant, and 2,2Ј-bipyridine as stabilizers. 14 This study investigated a low-cost selective plating technique that does not require etching copper layers. The quality of the deposited Cu fil...

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“…Ying et al [6] showed that deposition rate was increased with the addition of NH 4 F when the NH 4 F concentration was below 10 g/L in electroless Ni-P solution. In the study of Lantasov et al [7], reasonable stability was obtained in the temperature range between 20°C and 40°C for electroless copper plating bath. A technique which combines electroless plating and osmosis was proposed by Souleimanova et al [8].…”

Section: Introductionmentioning

confidence: 92%

“…EDTA formed a highly stable palladium complex and provided better stability of plating bath when compared to the other organic stabilizers used. High EDTA:Pd molar ratios (>14) were chosen for high bath temperatures (>70°C) [7,12]. Plating bath became unstable because of insufficient EDTA and the system had too great a stability because of excess EDTA.…”

Section: Studies Examining Bath Temperature As a Parametermentioning

confidence: 99%