Advanced BEOL integration using porous low-k (k=2.25) material with charge damage-less electron beam cure technique

As a practical curing technique of low-k material for 32-nm BEOL technology node, we demonstrated that electron beam (e-beam) irradiation was effective to improve film properties of nano-clustering silica (NCS). We confirmed that by using optimized e-beam cure condition, NCS was successfully hardened without degradation of dielectric constant and the Young's modulus increased by 1.7 times compared with that of thermally cured NCS. We fabricated two-level Cu wirings layers with NCS cured by optimized e-beam cure technique. The e-beam cure dramatically enhanced the lifetime of time-dependent dielectric breakdown (TDDB) of interlayer dielectrics. We also examined the influence of the charge damage to the MOSFETs under e-beam cured NCS layer and confirmed that there was no e-beam charge damage to the Ion-Ioff characteristics and reliability of MOSFETs with the optimized e-beam cure.