Plasma atomic layer etching of ruthenium with surface fluorination and ion bombardment
The plasma atomic layer etching (ALE) process for Ru was developed with surface fluorination and ion bombardment. We employed two methods for surface fluorination: (i) fluorocarbon deposition using CHF3 or C4F8 plasmas and (ii) chemisorption and diffusion with CF4 plasma. C4F8 plasma generated a more fluorine rich fluorocarbon layer on the Ru surface compared with CHF3 plasma, and a higher etch per cycle (EPC) of 1.5 nm/cycle was achieved with C4F8 plasma, in contrast to the 0.6 nm/cycle achieved with CHF3 plasma. Moreover, chemisorption and diffusion with CF4 plasma yielded an EPC of 1.2 nm/cycle. The ALE process using CHF3 plasma shows the lowest fluorine residue and lowest surface roughness compared with the ALE process using C4F8 and CF4 plasmas.
