bamboo structure

**Bamboo Structure** is a **desirable microstructural configuration in copper interconnects** — where each grain spans the entire width of the wire, creating grain boundaries that run perpendicular to the current flow direction, effectively blocking electromigration along grain boundary paths. **What Is Bamboo Structure?** - **Appearance**: Like a bamboo stalk — segments separated by transverse boundaries. - **Condition**: Grain size > wire width. Achieved through proper anneal and narrow linewidths. - **Effect**: No continuous grain boundary path along the current direction -> blocks EM diffusion along grain boundaries. **Why It Matters** - **EM Resistance**: Bamboo-structured lines have 10-100x longer electromigration lifetime than polycrystalline lines. - **Scaling Benefit**: As wires get narrower, bamboo structure becomes easier to achieve (grain size exceeds wire width). - **Dominant Path Shift**: With grain boundary EM blocked, the Cu/cap interface becomes the dominant failure path. **Bamboo Structure** is **grain engineering for reliability** — arranging crystal boundaries to create roadblocks against the electron-wind-driven migration of copper atoms.