Interconnect processes

Which correctly describes backside power delivery, which is being introduced in advanced logic?

  1. AA method that supplies no power from outside the chip
  2. BA method that replaces all wiring with optical fibers
  3. CA method that places power wiring on the back side of the wafer, freeing the front-side wiring for signals and reducing voltage drop and routing congestion
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Answer: C. A method that places power wiring on the back side of the wafer, freeing the front-side wiring for signals and reducing voltage drop and routing congestion

Conventionally, signal and power wiring were all built in the wiring layers above (on the front side of) the transistors. In backside power delivery, the wafer is thinned and power wiring is placed on the back, supplying power to transistors from below. Power wires can be thick and short, and front-side wiring can be used for signals.

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More Interconnect processes questions

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