Interconnect processes

What is the main purpose of the technique that makes part of the insulator between wires a cavity (air gap)?

  1. ATo increase the mechanical strength of the wiring
  2. BTo reduce capacitance between wires (air has a relative permittivity of about 1)
  3. CTo reduce wire resistance
Show answer and explanation

Answer: B. To reduce capacitance between wires (air has a relative permittivity of about 1)

Air (or vacuum) has a relative permittivity of about 1, lower than any insulating material, so making the space between wires a cavity greatly reduces capacitance between them. Because of challenges in mechanical strength and heat dissipation, it is used only in layers where capacitance reduction matters most.

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More Interconnect processes questions

  1. Which correctly describes backside power delivery, which is being introduced in advanced logic?
  2. What is the phenomenon called in which current flowing through the resistance of power wiring lowers the supply voltage that reaches circuits?
  3. 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?
  4. What is the main purpose of placing a cap layer such as cobalt on top of copper wiring?
  5. In Black's equation for wire lifetime under electromigration, which factors shorten the lifetime?