Interconnect processes

What is the phenomenon called in which electroplated Cu films, simply left at room temperature, grow larger grains over time and drop in resistivity?

  1. AElectromigration
  2. BStress migration
  3. CSelf-annealing
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Answer: C. Self-annealing

As-plated Cu films have small, unstable grains that recrystallize and grow at room temperature over hours to days, lowering resistivity. This is called self-annealing. To stabilize properties, a heat treatment is generally done after plating before proceeding to CMP.

  • A. Electromigration is current-driven atomic migration.
  • B. Stress migration is stress-driven atomic migration that forms voids.
  • C. Correct. It is recrystallization proceeding at room temperature.
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