Interconnect processes

When copper wires become very narrow, what is the main reason their effective resistivity rises?

  1. ABecause the wire temperature drops
  2. BBecause surface and grain-boundary scattering of electrons increase, and the high-resistance barrier layer takes up a larger share
  3. CBecause copper turns into a semiconductor
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Answer: B. Because surface and grain-boundary scattering of electrons increase, and the high-resistance barrier layer takes up a larger share

When wire width approaches the electron mean free path (tens of nm in copper), scattering at the wire surfaces and grain boundaries increases and resistivity rises. In addition, the barrier layer, which needs a certain thickness, occupies a larger share of the cross-section. New wiring materials such as cobalt and ruthenium are therefore being considered.

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More Interconnect processes questions

  1. In multilevel interconnects, what is the main reason upper-level wires are made wider and thicker?
  2. What is the main purpose of the technique that makes part of the insulator between wires a cavity (air gap)?
  3. Which correctly describes backside power delivery, which is being introduced in advanced logic?
  4. What is the phenomenon called in which current flowing through the resistance of power wiring lowers the supply voltage that reaches circuits?
  5. What is the phenomenon called in which, through capacitive coupling between adjacent wires, a signal change on one wire appears as noise on the other?