Interconnect Technology With h-BN-Capped Air-Gaps

To allow air-gaps with a large void size within a metal spacing, we propose the use of h-BN as an airgap capping layer, which suspends the inter-metal dielectric in a CMOS back-end-of-line (BEOL) process. The fabrication process, based on the transfer of h-BN to seal airgap regions, is discussed, including the use of Al2O3 on h-BN film for mechanical stability, and the consequence of thermal expansion coefficient mismatch in the materials introduced. A capacitance reduction of up to 50% is achieved through the large void size in the h-BN-capped air-gap technology. Demonstration of the proposed air-gap technology at μm dimension for top-level metalization is presented. The compromise on Young's modulus for a low effective-κ is measured and benchmarked against typical values in low-κ technology.