Pd Seeding with the Sonochemical Method for Application of Cu Electroless Deposition to Cu Metallization

Abstract

A sonochemical Pd seeding method for Cu electroless deposition (Cu ELD) is introduced in this study. Pd seeds, used as catalysts for Cu ELD, were deposited on a Ta/TaN diffusion barrier by ultrasound irradiation. The existence of Pd seeds on the substrate by irradiation was confirmed with X-ray photoelectron spectroscopy and atomic force microscopy. Cu ELD on the Pd-seeded substrate was successfully achieved. The formation of an electroless Cu film was strongly affected by the process parameters for sonochemical Pd seeding, such as the distance between the tip of the ultrasonic probe and a substrate, chemical composition of the seeding solution and ultrasound irradiation time. Those parameters were decisive factors in changing the deposition uniformity and number density of the Pd seeds. From the parametric study, we obtained a continuous electroless Cu film with good adhesion strength and low resistivity at the optimum condition.

A critical review of copper electroless deposition on glass substrates for microsystems packaging applications

“…Surface activation methods and changes in the reducing agent have little effect on the crystalline structure [88]. Typically, electroless deposits are homogeneous, dense, smooth, and bright [89][90][91]. The growth mechanism of electroless deposition is as follows: (i) dispersed reactant is adsorbed at the defect site at which reduced metal shows catalytic activity, and (ii) agglomerated copper granules are formed from nano-sized copper grains.…”

Enhancement of Seeding and Electroless Cu Plating on TaN Barrier Layers: The Role of Plasma Functionalized Self-Assembled Monolayers

“…8,9 In order to bind catalytic particles effectively, some novel methods, such as sonochemical synthesis of Pd seeds, have been adopted that create seeds of densities up to 1 × 10 15 m −2 . 10 Moreover, selfz E-mail: gschen@fcu.edu.tw assembled monolayers (SAMs) have recently been considered as significant components for microelectronic copper metallization, acting as seed-trapping layers, diffusion barriers, or pore-sealants particularly for porous dielectric materials. [11][12][13][14][15] Nonetheless, literature on direct plating of copper on transition metal and related nitride barrier materials via an SAM seed-trapping layer is largely missing.…”