Interconnect processes

Why has an Al-Cu alloy with about 0.5% copper been used for aluminum wiring?

  1. ATo improve resistance to electromigration
  2. BTo greatly lower resistivity
  3. CTo change the color of the wiring
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Answer: A. To improve resistance to electromigration

Pure aluminum wiring readily formed voids and hillocks through current-driven atomic migration (electromigration). Adding a little copper makes copper segregate to grain boundaries and suppresses the migration of aluminum atoms along them, greatly extending lifetime.

  • A. Correct. It improves electromigration resistance.
  • B. Adding a little copper actually raises resistivity slightly.
  • C. It is not for changing color.
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More Interconnect processes questions

  1. What is the phenomenon called in which electroplated Cu films, simply left at room temperature, grow larger grains over time and drop in resistivity?
  2. What is the main purpose of the design practice of placing two or more vias, rather than one, wherever possible to connect upper and lower wires?
  3. Which term refers to the contacts and local interconnects that connect the transistors to the multilevel wiring?
  4. In scaled multilevel wiring, what is the main reason via resistance has become a problem?
  5. Which statement about the capacitance of a wire is correct?