voiding in copper

**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.