Electrochemical Deposition of Nanoscaled Palladium Catalysts for 65 nm Copper Metallization

Abstract

The preparation of nanoscaled palladium ͑Pd͒ particles for catalyzation of electroless copper ͑Cu͒ plating has been investigated in this research. Nanosized Pd catalysts were electrochemically deposited on Si/SiO 2 /Ta x N substrates using displacement activation and sensitization activation, and their formation and microstructures were characterized. By displacement activation, large Pd particles with nonuniform size distribution from 20 to 200 nm are observed, resulting in subsequent rough and discontinuous Cu films electrolessly deposited on these Pd catalysts. In comparison, tremendous, small, and uniform Pd nanoparticles of about 10 nm are obtained by sensitization activation as fine nucleation sites for following electroless deposition of smooth and conformal Cu films. Nucleation, growth, coalescence, and then connection and film growth steps are observed in the formation process of Cu films. No preferred orientation of both electrolessly deposited Cu films is found. Well-controlled, electrochemically deposited nanoscaled Pd catalysts and uniform Cu films can be used as 65 nm Cu interconnect metallization.When the sizes of material structures are scaled down to nanometers, surfaces will occupy tremendous portions of whole materials and play very important roles. Surface effect, small-size effect, and even quantum effects are thus caused and severely affect the physical and chemical properties of these nanosized materials. Especially the insufficient coordination sites and high surface energy resulting in the high activity of these large amounts of surface atoms renders the application of nanosized materials to catalysts very possible. 1 For example, nickel, iron, and cobalt ferromagnetic nanoparticles have attracted a lot of interest as catalysts for the preparation of carbon nanotubes. 1 Copper with low electrical resistivity, good mechanical properties, and high electromigration resistance is used for interconnect metallization in dual-damascene structures of ultralarge-scale integrated ͑ULSI͒ circuits. 2-4 Electrochemical Cu plating, one of the Cu deposition techniques, becomes much attractive in semiconductor manufacturing industry because of its low processing temperature, high step coverage, high selectivity, and low cost. 4-7 However, sputtered Cu seed layers are still necessary for Cu electroplating, while their deposition technique is not adequate due to the insufficient gap-filling capability when the linewidths of integrated circuits ͑ICs͒ for next generation decrease to 65 nm. 8 Since that, the growth of Cu films with high selectivity and good step coverage by electroless deposition has been intensively studied. [9][10][11][12][13][14][15] One of the most important factors to influence the quality and morphologies of the electrolessly deposited Cu films is the activation step to seed the inert substrates prior to the nucleation and growth of Cu films. A large amount of uniformly distributed, nanoscaled catalysts dominates the success of activation process and subsequent electroless plating. Two ...

Electrochemical formation of intermediate layer for Co/Pd multilayered media

“…4(b)). The effect of SnCl 2 pretreatment on the morphology of the Pd deposits is described in detail elsewhere [8,14]. The decrease in the size of Pd seeds was reported to reduce the average [Co/Pd] n grain diameter [8], and thus, the similar effect was expected in this study.…”

Electroless- and Electroplating of Cu(Re) Alloy Films for Self-Forming Ultrathin Re Diffusion Barrier

“…26,27 A pure Cu or a Cu(Re) alloy film of about 150 nm thick was deposited on the catalyzed substrates in an EL Cu or EL Cu(Re) solution, as listed in Table I, at 50-60…”

“…[26][27][28] Three mixed solutions with different EL Cu and EL Re composition ratios (EL Cu: EL Re = 10:1, 10:2 and 10:3) were attempted for the EL Cu(Re) depositions, and the thermal stability of the deposited alloy films under an annealing at 600…”

“…Because a layer of densely packed Pd nanoparticles (with a size of several nm) that had been prepared on the surface of Si substrates for catalyzing the subsequent EL Cu(Re) deposition 26,27 might also inhibit the Cu/Si interdiffusion, the EL Cu(Re) thus showed a better thermal stability than the EP Cu(Re) without the Pd layer did. Figure 6a plots the ESCA elemental concentration distributions (depth profiles) in a 400…”

A Study on Seed Damage in Plating Electrolyte and Its Repairing in Cu Damascene Metallization

“…Surface activation was carried out via Sn sensitization ͑in 0.03 M SnCl 2 and 1.94 M HCl solution for 120 s͒ and Pd activation ͑in 0.56 mM PdCl 2 and 0.08 M HCl solution for 20 s͒ as used for electroless plating on the Ta substrate. [13][14][15] Four-point probe analysis ͑Chang Min Co., CMT-SR 1000N͒, a field-emission-scanning electron microscope ͑FESEM, JEOL, JSM-6330F͒, an X-ray photoelectron spectroscope ͑XPS, Kratos, AXIS͒, an X-ray diffractometer ͑XRD, Bruker, D8 Advance͒, and an atomic force microscope ͑AFM, Park SYSTEMS, XE-150͒ were used to analyze the change in the seed properties during the damage and the repair. Figure 1 shows the changes in the surface morphology and the sheet resistance of the 10 nm thick seed layer during immersion in the plating electrolyte.…”