Multi-Level Cu Interconnects Integration and Characterization with Air Gap as Ultra-Low K Material Formed using a Hybrid Sacrificial Oxide / Polymer Stack

The introduction of air gaps in multi-level Cu interconnect stacks will be mandatory to achieve high performance signal propagation characteristics for advanced technology node. In this paper, air cavities were successfully introduced in a two-metal level interconnect stack using respectively a polymer and a sacrificial SiO₂ at via and metal levels. Combined with a diluted HF chemistry and specific HF diffusion pathways patterned in a SiC liner, the ability to localize the introduction of air cavities in a dedicated large electrical area was demonstrated. Electrical characteristics and mechanical simulations demonstrated the interest of the approach with respect to ultra-low K material integration issues.