Optimization of Diamond Polishing Process for Sub-Nanometer Roughness Using Ar/O₂/SF₆ Plasma

Area of Science:

• Materials Science
• Surface Engineering
• Nanotechnology

Background:

• Single-crystal diamond possesses unique properties valuable for advanced applications.
• Surface roughness is a critical factor limiting diamond's performance in high-precision fields.
• Existing surface modification techniques require optimization for diamond.

Purpose of the Study:

• To optimize inductively coupled plasma (ICP) polishing parameters for reducing single-crystal diamond surface roughness.
• To investigate the influence of various etching parameters on diamond surface topography.
• To achieve ultra-smooth diamond surfaces for enhanced optical applications.

Main Methods:

• Utilized ICP polishing to etch single-crystal diamond samples.
• Employed atomic force microscopy (AFM) to quantify surface roughness before and after etching.
• Systematically varied gas flow ratios (Ar/O2/SF6), ICP power, RF bias power, chamber pressure, and etching time.

Main Results:

• Optimal parameters identified: 40/50/10 sccm Ar/O2/SF6, 200 W ICP power, 40 W RF bias power, 20 mTorr pressure, and 10 min etching time.
• Etching time and SF6 flow rate increased roughness; higher ICP/RF power reduced roughness but induced nanostructures.
• Lower chamber pressure minimized roughness increase, while higher pressure exacerbated it.

Conclusions:

• The optimized ICP polishing process effectively reduces single-crystal diamond surface roughness.
• Achieved a 74.7% reduction in roughness (from 2.22 nm to 0.562 nm) using optimized parameters.
• The enhanced surface quality makes diamond more suitable for demanding high-precision optical applications.