Interconnect processes

What is the main reason the wiring material of advanced LSIs was changed from aluminum (Al) to copper (Cu)?

  1. ALower resistivity and higher electromigration resistance
  2. BIt is easier to process by dry etching
  3. CIts adhesion to oxide is so high that no barrier layer is needed
Show answer and explanation

Answer: A. Lower resistivity and higher electromigration resistance

Copper's resistivity is about 60% that of aluminum, reducing wiring delay, and it is also more resistant to electromigration. On the other hand, copper is hard to dry-etch and diffuses easily into insulators, so it is formed by the damascene process and surrounded by barrier layers such as Ta and TaN.

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More Interconnect processes questions

  1. Which correctly describes the damascene process commonly used to form copper wiring?
  2. What is the main purpose of using low-k (low dielectric constant) materials for interlayer dielectrics?
  3. What is the main purpose of barrier metals such as Ta and TaN in copper wiring?
  4. Which correctly describes a via in multilevel interconnects?
  5. If a wire's length is doubled without changing its cross-section or spacing, approximately how many times larger does its RC delay become?