Electroless Plating is a chemical deposition method that deposits metal without an external electrical current — using a chemical reducing agent in solution to drive the metal reduction reaction autocatalytically on a catalytic surface, enabling selective deposition on specific materials.

How Does Electroless Plating Work?

• Reaction: $M^{n+} + Red ightarrow M^0 + Ox$ (Metal ions reduced by chemical agent).
• Catalyst: Deposition only occurs on catalytic surfaces (e.g., Pd-activated or existing metal surfaces).
• Materials: CoWP, CoB, NiP are common for semiconductor capping layers.
• Selectivity: Deposits only on metal (Cu) surfaces, not on dielectric — no lithography needed.

Why It Matters

• Selective Cu Capping: CoWP electroless cap on Cu lines improves electromigration lifetime by 10x vs. dielectric cap.
• No Lithography: Self-selective deposition reduces process steps and cost.
• Barrier Application: Potential for selective barrier deposition on Cu without blanket PVD/ALD.

Electroless Plating is self-directed metal deposition — a chemistry-driven process that puts metal exactly where it's needed without masks or electrical connections.