Controllable Cyclic Wet Etching of Molybdenum at Room Temperature

A cyclic wet etching process for molybdenum (Mo) film utilizing ammonium persulfate (APS) solution at room temperature has been developed, enabling precise etching of the Mo film. The etch per cycle (EPC) of the Mo film was determined to be 0.3 nm/cycle in the 1 wt % APS solution. The surface roughness after the etching process was found to be lower than that of the as-deposited sputtered Mo film and had good consistency after multiple etching cycles. The lateral recess of the Mo layer in the Mo/SiO₂ stack structures, as well as the controllable recess of the Mo nanowires, was successfully demonstrated. The controllable Mo etching by APS was due to a passivation-dissolution mechanism, which was supported by complementary measurements and density functional theory calculation.