Buried Power Rail Metal exploration towards the 1 nm Node

This work reports metal exploration for buried power rail (BPR) and Via-to-BPR (VBPR) towards the 1 nm node. For tungsten, which is the first choice of BPR metal at the 3 nm node, we optimize W metallization stack to minimize line resistivity, together with ways to reduce W-BPR - W-VBPR contact resistance (R). For scaled BPR CDs at the 2 nm and 1 nm nodes, we introduce molybdenum at the BPR level and benchmark its R and electromigration against W and Ru metallization Additionally, Mo dry & wet, selective etch processes to enable Mo-BPR recess in fin/STI stack at fin pitch 24 nm, and a Mo wet clean process for VBPR contact formation are also demonstrated.

Automated summary

This study focuses on metal exploration for buried power rail (BPR) and Via-to-BPR (VBPR) for the 1 nm technology node, optimizing tungsten metallization stack for lower line resistivity and reducing contact resistance. Introducing molybdenum at the BPR level and comparing its performance with other metals for scaled BPR CDs, new Mo dry & wet etch processes were developed for Mo-BPR recess and VBPR contact formation.