The model of nano-scale copper particles removal from silicon surface in high pressure CO2+H2O and CO2+H2O+IPA cleaning solutions

This study focuses on the description of static forces in a system with a fluid phase entrapped between nano-scale particles and a surface. Equilibrium separation distance (EDS) and net adhesion force (NAF) of a particle adhering on substrate can be used as the guideline for evaluating extend of the particle cleaning. Calculations demonstrate that pressure can significantly alter the static force balance of an adhered particle on substrate, i.e., increasing the pressure of the cleaning system decreases the NAF between spherical copper particle and silicon surface entrapped with medium. The value of NAF decreases and that of ESD increases with increased pressure as the submersion height of a particle is given. The NAF (or ESD) of a particle on substrate turns to small (or large) as IPA is added into CO₂-H₂O system, suggesting that adding IPA in CO₂-H₂O system has the potential to facilitate particle disengagement from surface. For particles with different dimension under high pressure, the NAF is nearly same as the submersion height is given, and the ESD increases with increased particle radius, which means that the particle with larger dimension can be removed more easily.