Mechanism of Bismuth Stimulated Bottom-up Gold Feature Filling.

Area of Science:

• Electrochemistry and Materials Science
• Nanofabrication and Thin Film Deposition

Background:

• Understanding bottom-up fabrication is crucial for advanced microelectronic device manufacturing.
• Gold (Au) electrodeposition in trenches and vias requires precise control over deposition mechanisms.
• The role of additives like Bismuth (III) ions (Bi3+) in modifying Au deposition kinetics is not fully elucidated.

Purpose of the Study:

• To explore the mechanism of Bi3+-stimulated bottom-up Au filling and self-passivation in trenches and vias.
• To quantify the impact of electrolyte components (Na3Au(SO3)2, Na2SO3, Bi3+) and potential-dependent kinetics on Au electrodeposition rate.
• To apply derived parameters within the Curvature Enhanced Accelerator Coverage (CEAC) model to simulate trench filling.

Main Methods:

• Experimental quantification of electrolyte component impacts on Au electrodeposition rate.
• Application of derived kinetic parameters within the CEAC model for simulation.
• Analysis of Bi adsorption effects and electrolyte composition gradients on deposition localization.

Main Results:

• Bi adsorption accelerates Au deposition rate non-linearly around a critical coverage.
• Electrolyte composition gradients accentuate deposition away from the feature opening, localizing active deposition to feature bottoms.
• Weakening concentration gradients and kinetics reduce Bi coverage, terminating bottom-up growth and leading to self-passivation.

Conclusions:

• Bi3+ ions are key to achieving bottom-up Au filling and self-passivation in trenches and vias.
• The CEAC model, incorporating experimental parameters, accurately simulates the observed deposition features.
• Control over electrolyte composition and deposition kinetics is essential for directed nanofabrication.