Buried Power Rail Metal exploration towards the 1 nm Node

Abstract

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.