Effect of Ethanolamines on the Electroless Deposition of Copper on Functionalized Organic Surfaces

Abstract

Electroless deposition (ELD) is widely used in industry to deposit metals because it is inexpensive and compatible with organic materials. The deposition rate and deposited film properties critically depend on the reducing agent, complexing agent, and bath pH and temperature as well as bath additives. We have investigated the role of ethanolamine additives in the ELD of copper using the reducing agent dimethylamine borane on -CH- and -OH-terminated self-assembled monolayers (SAMs) adsorbed on gold. Three additives were studied: ethanolamine (EOA), diethanolamine (DEOA), and triethanolamine (TEOA). Both the chemical identity and concentration of the ethanolamine significantly affect the deposition process. We show that the Cu deposition rate is faster on -CH-terminated surfaces than on -OH-terminated SAMs because of the stronger interaction of the ethanolamines with the hydroxyl terminal group. In contrast to physical vapor deposition and other ELD processes, Cu deposits atop methyl-terminated SAMs using TEOA. However, using EOA and DEOA, copper penetrates through -CH-terminated SAMs to the Au/S interface. For -OH-terminated SAMs, copper is observed to penetrate through the SAM for all ethanolamines investigated. The amount of copper penetration through the SAM to the Au/S interface increases with ethanolamine concentration. These effects are attributed to an adsorption-inhibition mechanism and differences in the chelation of Cu in the deposition bath.

Synthesis, Characterisation and Cytotoxicity of Gold Nanowires for Ultra-Sensitive Biosensor Development

“…The primary limiting factor for constant electron transfer rate would be the TIPS reagent. [55]. During the synthesis reaction, in the absence of heat, a colour change occurs from a light orange to red followed by dark violet during the period of reaction as shown in Fig.…”

Electroless Metallization of the Elements: Survey and Progress

“…In a more recent study, Ellsworth and Walker have examined and demonstrated complex interactions among bath components at the substrate surface that influence plating. They use alkylthiol SAMs to alter Au substrate surface chemistry in conjunction with an EL Cu bath containing 32 mM CuSO 4 , 37 mM EDTA, 67 mM DMAB, and 300 mM of the amine additives, ethanolamine (EOA), diethanolamine (DEOA), or TEOA.…”

“…The use of boron-based reducing agents, ,− such as DMAB or BH 4 – , in EL Cu baths represents another alternative to HCHO. However, these reducing agents also present issues that limit their usage.…”

“…Their observations are consistent with earlier work by Plana et al,434 who used dual galvanic cells to separate the EL reactions involving DMAB oxidation and Cu II reduction for study. They report that MPT does not adequately describe EL Cu deposition for the DMAB baths because the oxidation and reduction reactions are not additively coupled due to the presence of side reactions (e.g., DMAB decomposition).In a more recent study, Ellsworth and Walker437 have examined and demonstrated complex interactions among bath components at the substrate surface that influence plating. They use alkylthiol SAMs to alter Au substrate surface chemistry in conjunction with an EL Cu bath containing 32 mM CuSO 4 , 37 mM EDTA, 67 mM DMAB, and 300 mM of EL plating occurs via an adsorption−inhibition mechanism in which initial physisorption of DMAB into the SAM, followed by dissociation and release of HN(CH 3 ) 2 into the aqueous solution and entrapment of the BH 3 within the SAM, occurs.…”

Effects of Silver Ions on High‐Speed Electroless Copper

“…It is commonly used to metallize the non‐conductive substrate followed by electroplating copper to a desired thickness. To simplify the manufacture process, one‐step electroless copper to the desired thickness is becoming more and more popular . To achieve that, the electroless copper has to have a high plating rate and a good film quality.…”