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.