Advanced Cu interconnects using air gaps

The integration of air gaps for advanced Cu interconnects is mandatory to achieve the performances required for high performance integrated circuits (ICs). The interest of their introduction as a function of the chosen architecture, i.e. hybrid (i.e. air cavities at metal levels with a low-K material at via level) or full homogenous air gaps with an effective relative constant close to 1, is discussed in terms of signal propagation requirements for delay, crosstalk and delay increased by crosstalk. The different approaches currently investigated within the microelectronic community are classified into two main categories depending on the use of a non-conformal plasma enhanced chemical vapor deposition (PE-CVD) including innovative alternatives or the removal of a sacrificial material during a specific technological operation. While the first technique,, faces many integration issues that can be alleviated at the detriment of the global performances, the second approach may be all the more promising as well-known materials such as USG or SiOC are now introduced as sacrificial dielectrics as an alternative to degradable polymers. However, it is evidenced from published results that air gaps integration maturity permits their introduction for the 32nm technology node high performance ICs.