Voiding in Copper is a reliability failure mechanism where empty cavities (voids) form within copper interconnect lines or vias — caused by stress migration, electromigration, or incomplete electroplating fill, leading to increased resistance or open-circuit failures.

Types of Cu Voids

• Plating Voids: Form during ECP due to poor superfill chemistry, seed discontinuity, or pinch-off at narrow trench openings.
• Stress-Induced Voids (SIV): Form during thermal cycling as copper retracts from interfaces under tensile stress.
• Electromigration Voids: Form at cathode end of a line under sustained current flow (mass transport away from this region).
• Location: Most critical at via bottoms (where current density is highest).

Why It Matters

• Resistance Increase: Even a small void that partially blocks the via causes significant resistance rise.
• Open Failure: A void spanning the full via cross-section causes a complete open circuit.
• Reliability: Voiding is the #1 copper interconnect reliability concern at advanced nodes.

Voiding is the silent killer of copper wires — invisible cavities that grow over time until they sever the electrical connection.