Plasma atomic layer etching of molybdenum with surface fluorination for next-generation interconnect

Plasma Atomic Layer Etching (ALE) process for molybdenum (Mo) with surface fluorination and ion bombardment. The Mo surface was fluorinated by depositing fluorocarbon layers with CHF3 or C4F8 plasmas, and the fluorinated surface was removed by Ar plasma. The fluorocarbon layers on the Mo surfaces were generated with CHF3 or C4F8 plasmas. The etch per cycle (EPC) of Mo was determined to be 0.8 nm/cycle for CHF3 plasma and 2.8 nm/cycle for C4F8 plasma. The ALE window region was identified at bias voltages between 100 V and 225 V. The EPC of Mo increased with increasing Ar plasma time and exhibits self-limiting properties at 150 s for the CHF3 plasma and 420 s for the C4F8 plasma. Fluorine residue after ALE was as low as 4%, which is lower than radical etching and RIE.