Covalent Binding of Pd Catalysts to Ligating Self‐Assembled Monolayer Films for Selective Electroless Metal Deposition

Abstract

A new approach for the selective electroless (EL) metallization of surfaces is described. Surfaces are modified with a chemisorbed ligand-bearing organosilane film, and then catalyzed with an aqueous Pd(II) catalyst solution. The catalyzed substrate is then immersed in an EL metal deposition bath to complete the metallization process. The ligating surfaces are produced by molecular self-assembly of 2-(trimethoxysilyl)ethyl-2-pyridine (PYR) on silicon or silica substrates. The catalyst consists of chloride-containing aqueous Pd(II) solutions buffered at pH 5.0 to 6.4; oligomeric chloro and/or hydroxo-bridged Pd(II) complexes act as the catalytic species at the surface. The activity of the catalyst has been characterized and modeled as a function of solution pH, [C1-], and time from preparation. Adhesion of the Pd(II) EL catalyst to the substrate involves covalent bond formation with the surface ligand. An average minimum Pd(II) level on the surface of -10 '~ Pd atom cm 2 is shown to be necessary to initiate EL metallization of the substrate with an EL Co bath. This process involves fewer steps and displays improved selectivity compared to processes that involve a conventional Pd/Sn catalyst. Fabrication of high resolution metal patterns using the new metallization chemistry in conjunction with deep UV patterning of PYR films is demonstrated.

The hydrolysis and precipitation of Pd(II) in 0.6molkg−1 NaCl: A potentiometric, spectrophotometric, and EXAFS study

“…The Pd-Cl distance in the Pd(OH) 1.73 Cl 0.27 solid of 2.185 Å is 0.2-0.3 Å shorter than those of monomeric Pd(II)-chloride species measured in aqueous solutions (Valle and Ettorre, 1994;Hellquist et al, 1996;Caminiti et al, 1996Caminiti et al, , 1998 and calculated in the gas phase (Table 2; Bray et al, 1996;Deeth and Elding, 1996;Boily and Seward, 2005). It is however close to the EXAFS-derived value of 2.25 Å obtained by Troitskii et al (1995) on a similar material and most likely arises from the bridged coordination of chloride between two palladium atoms (Wyatt, 1966;Dressick et al, 1994), as illustrated in Fig. 6a.…”

“…The aqueous speciation of palladium(II) is considerable interest for geochemical (Lee, 1983;Kump and Byrne, 1989;Wood et al, 1989) and catalytic (Dressick et al, 1994;Troitskii et al, 1996) settings. The fate and transport of palladium in the environment as well as the formation of palladium deposits under hydrothermal conditions are in particular of crucial environmental and economical importance.…”

“…Palladium(II) is one of the most hydrolysable metal ions (Baes and Mesmer, 1976) and its hydrolysis products have consequently been studied under a variety of conditions (Wyatt, 1966;Izatt et al, 1967;Kazakova and Ptitsyn, 1967;Nabivanets and Kalabina, 1970;Rund, 1970;Milić and Bugarčić, 1984;Mountain and Wood, 1988;Kump and Byrne, 1989;Wood et al, 1989Wood et al, , 1992Wood, 1991;Byrne and Kump, 1993;Tait and Janecky, 1993;Tait et al, 1991;Troitskii et al, 1993Troitskii et al, , 1995Troitskii et al, , 1996Dressick et al, 1994;Didillon et al, 1998;van Middlesworth and Wood, 1999;Byrne and Yao, 2000;Cosden and Byrne, 2003). Partially hydrolyzed Pd(II) species can crosslink and form larger polymeric/polynuclear units that are stable as coiled [Pd(OH) 2 ] n chains of about 20 Å in diameter (Troitskii et al, 1993(Troitskii et al, , 1995(Troitskii et al, , 1996.…”

“…They can also occur as mixed chloride-hydroxide species in chloride-rich solutions, as first shown by Wyatt (1966) (Pd(OH) 1.6 Cl 0.4 ) and later by Byrne and Yao (2000) (Pd(OH) 1.73 Cl 0.27 ), and control the solubility of Pd(II) under these conditions. Mixed chloride-hydroxide aqueous species (Kump and Byrne, 1989;Byrne and Yao, 2000;Cosden and Byrne, 2003), such as PdCl 3 OH 2À , are equally important and are likely key reactive intermediates in the formation of insoluble palladium hydroxides solids during which coordinated chloride ions are progressively replaced by hydroxyl ions (Wyatt, 1966;Dressick et al, 1994). Reverse reactions can also take place involving solid phases, such as in the solubility experiment of van Middlesworth and Wood (1999) where dissolved chloride ions induce a phase transformation from the PdOAEH 2 O starting material to Pd(OH) 1.72 Cl 0.28 (Byrne and Yao, 2000).…”

Functionalization of Hydrogen-Terminated Si(100) Substrate by Surface-Initiated RAFT Polymerization of 4-Vinylbenzyl Chloride and Subsequent Derivatization for Photoinduced Metallization

“…41, 49 The other new doublet with intermediate BEs at about 336.5 and 341.5 eV for the respective Pd 3d 5/2 and Pd 3d 3/2 peak components is associated with the formation of the Pd-N complex (the Pd* species). 41, 50 The data in Figure 9b indicate that the extent of conversion of the Pd(II) species to Pd(0) species is about 43% after 30 min of UV irradiation.…”