Electroless Cobalt Via Pre-Fill Process for Advanced BEOL Metallization and Via Resistance Variation Reduction

While processes have been developed to reduce nominal via resistance due to resistive Ta/TaN barrier layers, little effort has been made to show improvements to counteract the shrinking process window for via resistance with technology dimension. An electroless Co via-prefill process can improve nominal resistance, and in this paper, we quantitatively demonstrate improvement in process variability. Through process modeling with virtual fabrication, we also scale this prediction to 7 nm where the variability of the typical Ta/TaN approach is 50% higher with Co via-prefill.