Competitive-adsorption-resistant interfacial regulation by 2-mercaptopyridine enables selective copper microvia...

Area of Science:

• Electrochemistry
• Materials Science
• Surface Chemistry

Background:

• Selective copper superfilling in microvias is crucial for advanced electronics.
• Understanding co-additive interactions at interfaces is key to controlling copper deposition.
• The effectiveness of levelers in the presence of accelerators is not well understood.

Purpose of the Study:

• To investigate the interfacial mechanisms of 2-mercaptopyridine (2-MP) as a leveler in copper electrodeposition.
• To elucidate how 2-MP stabilizes inhibitory states against accelerator displacement.
• To provide insights into competitive adsorption for designing effective levelers.

Main Methods:

• Galvanostatic measurements (GMs), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS).
• Microvia filling tests, surface characterization, X-ray photoelectron spectroscopy (XPS).
• Density functional theory (DFT) and molecular dynamics (MD) simulations.

Main Results:

• 2-MP adsorbs on copper via dual-site chemisorption (N and S atoms), forming a stable inhibitory state.
• This adsorption suppresses bis-(3-sulfopropyl) disulfide (SPS)-induced depolarization, maintaining inhibition under polyethylene glycol (PEG)/SPS conditions.
• A deposition-rate gradient, driven by 2-MP/PEG at the via mouth and SPS at the bottom, enables void-free filling with a thin overburden (23-36 μm).
• 2-MP offers superior control over SPS occupation and filling selectivity compared to Janus Green B (JGB).

Conclusions:

• Competitive-adsorption resistance is a key descriptor for evaluating small-molecule levelers.
• 2-MP's dual-site chemisorption provides robust control over copper electrodeposition in confined geometries.
• Understanding interfacial competition is vital for advancing copper plating technologies.