Materials Engineering for Future Interconnects: “Catalyst-Free” Electroless Cu Deposition on Self-Assembled Monolayer Alternative Barriers

Abstract

An alternative bottom-up Cu electroless deposition (ELD) method without other catalyst material activation is the focus of this paper. The process consists of reducing the Cu ions in a solution via standard reducing agents such as dimethylamine borane. The reaction pH and ionic strength values can be modulated to impart to the metallic Cu particle surface an opposite charge with respect to the deposition substrate functionalized by the 3-aminopropyltrimethoxysilane (APTS) self-assembled monolayer used as a diffusion barrier. At neutral pH, the negatively charged Cu particles are electrostatically attracted by the positively charged NH2 groups, and they can form strong interfacial complexes if the required activation energy budget is supplied. A design of the experiment is carried out to optimize the critical deposition parameters such as temperature, time, Cu ion concentration, and pH. The formed ELD Cu nuclei positioned preferentially on the APTS layer, showing a wetting behavior that is accentuated upon anneal, leading to a decrease in surface roughness that corresponds to an increase in film closure. The observed debonding energy of the ELD Cu/APTS surface is ca. 2.2J/normalm2 before anneal, while it reaches ca. 4.5 and 8J/normalm2 after a 10 min anneal under forming gas at 300 and 450°C , respectively.

Recrystallized ice-templated electroless plating for fabricating flexible transparent copper meshes

“…5d), which can be attributed to the reduced contact resistance between copper nanoparticles. 33 The quality of a transparent electrode could also be described in the form of a gure-of-merit (FoM ¼ s dc /s opc ), which can be calculated using eqn (3), where s dc and s opc represent direct current conductivity and optical conductivity, respectively. 41 Fig.…”

“…PET substrates were treated with oxygen plasma for 10 min, then immersed into a 5 mM APTES solution for 30 min. 33 To remove solvent residue and unreacted silane molecules, the as-prepared PET substrates were consecutively ultrasonically cleaned in toluene, acetone, deionized water, and dried with owing nitrogen. The fabrication of the copper meshes is shown schematically in Fig.…”

“…The electroless copper plating between the ice crystals could be initiated once the DMAB had diffused into the plating solution, due to the strong reduction of DMAB. [33][34][35] (V) The ice template was removed by washing with ethanol, and the copper meshes were le on the PET substrates. The statistical method followed our reported work.…”

Mechanism of Electroless Copper Deposition from [CuIIEDTA]2– Complexes Using Aldehyde-Based Reductants

“…2 By nature, electroless deposition does not require an external current supply (as required by electrodeposition 1 ), and thus, electroless deposition is ideally suited for deposition onto insulators, semiconductors, resistive electrodes, and micropatterned surfaces. 3,4 Electroless deposition of thin metallic Cu films is gaining interest for the fabrication of nanoscale interconnects in advanced microprocessors and memory devices. 4,5 Typically, the electroless Cu bath contains an aqueous solution of Cu 2+ stabilized at high pH using a complexant such as deprotonated ethylenediamine tetraacetic acid, EDTA 4− (aq) .…”

“…3,4 Electroless deposition of thin metallic Cu films is gaining interest for the fabrication of nanoscale interconnects in advanced microprocessors and memory devices. 4,5 Typically, the electroless Cu bath contains an aqueous solution of Cu 2+ stabilized at high pH using a complexant such as deprotonated ethylenediamine tetraacetic acid, EDTA 4− (aq) . An aldehydebased reducing agent, such as formaldehyde 6 (H 2 CO) or glyoxylic acid 7 [HC(O)COOH], enables chemical reduction of dissolved [Cu II EDTA] 2− (aq) to metallic Cu on the electrode surface.…”