Silicon Surface Modification Using C4F8+O2 Plasma for Nano-Imprint Lithography.

Area of Science:

• Materials Science
• Plasma Physics
• Surface Chemistry

Background:

• Octofluorocyclobutane (C4F8) is a key precursor in plasma-based surface modification.
• Understanding the interplay between feed gas composition and plasma characteristics is crucial for controlling surface properties.
• Silicon (Si) surface modification is vital for microelectronics and advanced material applications.

Purpose of the Study:

• To investigate the effect of C4F8+O2 feed gas composition on plasma parameters.
• To analyze the impact of varying O2 ratios on plasma-treated silicon surface characteristics.
• To establish correlations between plasma properties and resultant surface modifications.

Main Methods:

• Plasma diagnostics utilizing Langmuir probes.
• Plasma modeling to understand radical densities.
• Surface characterization via X-ray photoelectron spectroscopy (XPS) and contact angle measurements.

Main Results:

• Increasing O2 mixing ratio led to a monotonic decrease in CF(x) (x=1-3) radical densities.
• Fluorine (F) atom density exhibited non-monotonic behavior with changing O2 concentration.
• C4F8+O2 mixtures (O2 < 60%) resulted in Si surface modification through FC polymer film deposition.
• O2 ratios between 30%-60% effectively tuned surface energy and contact angle.

Conclusions:

• The O2 mixing ratio in C4F8 plasma significantly influences plasma parameters and radical species.
• Plasma treatment with C4F8+O2 enables controlled deposition of FC polymer films on Si surfaces.
• Tunable surface properties, including surface energy and contact angle, can be achieved by adjusting O2 concentration in the 30%-60% range.