Reliability degradation impact by ultra low-k dielectrics and improvement study for BEOL process beyond 28nm technology

As CMOS is being scaled down to 28nm node and beyond, BEOL process must use ultra low-K film as inter-metal dielectric (IMD) layers to reduce interconnection RC delay. Compared to low-K film, ultra-low K film (K≤2.5) is more porous, softer and more hydrophilic intrinsically, and easy to be damaged by process plasma, film stress, thermal and aqueous environments. The paper focuses mainly on the BEOL processes, such as etch PET, metallization, CMP, thermal treatment impact of ultra low-k dielectrics on reliability performance of electromigration (EM) and time-dependent dielectric breakdown (TDDB) or dielectric voltage breakdown (VBD). Some optimized BEOL processes with improved control of damage on porous low k materials could lead to an acceptable EM and TDDB performance.