Adsorption behavior of anionic polyelectrolyte for chemical mechanical polishing (CMP)

Area of Science:

• Materials Science
• Chemical Engineering
• Surface Chemistry

Background:

• Anionic polyelectrolytes are crucial additives in chemical mechanical polishing (CMP) slurries.
• Achieving high selectivity between silicon dioxide (SiO2) and silicon nitride (Si3N4) is vital for shallow trench isolation (STI) in semiconductor manufacturing.
• Ceria abrasives are commonly used in CMP, but understanding additive interactions is key to optimizing performance.

Purpose of the Study:

• To investigate the adsorption behavior of anionic polyelectrolytes on SiO2 and Si3N4 surfaces.
• To correlate adsorption characteristics with the selectivity of ceria slurry in CMP.
• To elucidate the mechanisms behind the differing removal rates of SiO2 and Si3N4 layers.

Main Methods:

• Adsorption isotherm analysis.
• Fourier Transform Infrared (FT-IR) spectroscopy.
• Contact angle measurements.
• Blanket wafer polishing experiments.

Main Results:

• Anionic polyelectrolytes exhibited significantly higher adsorption affinity for Si3N4 surfaces compared to SiO2 surfaces.
• FT-IR and contact angle measurements confirmed the preferential adsorption on Si3N4.
• CMP results demonstrated a strong correlation between polyelectrolyte adsorption isotherms and the observed selectivity.

Conclusions:

• The preferential adsorption of anionic polyelectrolytes on Si3N4 is the primary factor driving the high selectivity in ceria CMP.
• Understanding these surface interactions allows for the rational design of CMP slurries with tailored performance.
• This study provides insights into optimizing STI processes through controlled additive-surface interactions.