Interconnect processes

What film is commonly placed on top of Cu wiring to act both as a diffusion barrier toward the dielectric and as an etch stop?

  1. APhotoresist
  2. BPolysilicon
  3. CA dielectric cap such as SiCN
Show answer and explanation

Answer: C. A dielectric cap such as SiCN

The top of Cu wiring exposed by CMP is covered with a dielectric cap such as SiCN or SiN that prevents Cu from diffusing into the dielectric above and stops the via etch of the next level. Because its permittivity is relatively high, it is kept thin.

  • A. Photoresist is a temporary film for patterning.
  • B. Polysilicon is conductive and is not used as an insulating cap over wiring.
  • C. Correct. A dielectric cap such as SiCN is used.
Practice this topic Back to topic

More Interconnect processes questions

  1. In electromigration testing, wires shorter than a certain length show greatly extended lifetimes, with almost no degradation. What is this phenomenon called?
  2. When a wire becomes narrower than its grains so that grain boundaries line up across the wire, what is this structure called, and how does it affect electromigration?
  3. When high-frequency signals flow in a wire, what is the phenomenon called in which current concentrates near the conductor surface and the effective resistance rises?
  4. What is the design practice called in which active devices and wiring are placed directly beneath the bond pads used for wire bonding and the like?
  5. Which technique deposits a Cu alloy with a small addition of manganese or similar and, through annealing, lets a thin barrier form spontaneously at the interface with the dielectric?