Controllable Cyclic Wet Etching of Molybdenum at Room Temperature

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Precise etching of molybdenum (Mo) films is crucial for microelectronic and nanodevice fabrication.
• Existing etching methods may lack control over etch rate and surface morphology.
• Developing room-temperature, high-precision etching techniques is an ongoing challenge.

Purpose of the Study:

• To develop a cyclic wet etching process for Mo films using ammonium persulfate (APS) solution.
• To precisely control the etch depth and surface properties of Mo films.
• To investigate the etching mechanism for controllable Mo recess.

Main Methods:

• Cyclic wet etching of Mo films in 1 wt % ammonium persulfate (APS) solution at room temperature.
• Determination of etch per cycle (EPC) and surface roughness analysis (e.g., AFM).
• Demonstration of lateral recess in Mo/SiO2 stack structures and Mo nanowires.
• Density functional theory (DFT) calculations and complementary measurements to elucidate the etching mechanism.

Main Results:

• A cyclic wet etching process for Mo films was successfully developed.
• The etch per cycle (EPC) was precisely controlled at 0.3 nm/cycle.
• Etching resulted in lower surface roughness compared to as-deposited Mo films, with good consistency over multiple cycles.
• Controllable lateral recess in Mo/SiO2 stacks and Mo nanowires was achieved.
• A passivation-dissolution mechanism was identified as the basis for controllable Mo etching.

Conclusions:

• The developed cyclic wet etching process offers precise control over Mo film thickness and surface morphology.
• The APS-based etching method is suitable for creating controlled recesses in Mo layers and nanowires.
• The understanding of the passivation-dissolution mechanism provides a foundation for optimizing Mo etching processes.