Atomic layer etching of molybdenum with fluorination and ion bombardment

Atomic layer etching (ALE) process for Mo was developed with surface fluorination using CHF
3
or C
4
F
8
plasmas and ion bombardment using Ar plasma. The Mo surface was fluorinated with fluorocarbon generated by CHF
3
or C
4
F
8
plasmas, and fluorinated Mo was etched by Ar plasma. The C
4
F
8
plasma produced fluorine-rich fluorocarbon layer compared to the CHF
3
plasma and etch per cycle (EPC) of Mo was about 3 times higher in C
4
F
8
plasma than in CHF
3
plasma. EPC of Mo was investigated by changing the bias voltage of Ar plasma, and ALE window was confirmed in the range of 100 ~ 225 V. The EPC of Mo in the ALE window was determined to be 0.8 nm/cycle for CHF
3
plasma and 2.8 nm/cycle for C
4
F
8
plasma, and it was self-limited with increasing Ar plasma time. Fluorine-rich fluorocarbon layer on the Mo surface increases the EPC of Mo.