Interconnect processes

What is the role of the thin copper film sputtered before filling copper by electroplating?

  1. AA barrier against copper diffusion
  2. BA conductive layer that carries plating current (seed layer)
  3. CInsulation between layers
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Answer: B. A conductive layer that carries plating current (seed layer)

Electroplating deposits metal by passing current through the surface, so a conductive layer is needed all the way down the inside of the trench. A thin copper seed layer is therefore sputtered over the barrier before copper is filled by plating.

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More Interconnect processes questions

  1. What problems occur when copper filling is incomplete and a void remains in a via?
  2. If the spacing between adjacent wires in the same layer is halved, approximately how does the capacitance between them change? (Approximate as parallel plates.)
  3. Which technique forms vias self-aligned to wiring trenches to tolerate misalignment between upper and lower wiring layers?
  4. For wiring with a resistivity of 2 µΩ·cm, 1 mm long, with width and thickness of 100 nm each, approximately what is the resistance?
  5. Where are voids due to electromigration likely to form?