Surface modifications of silicon chips to reduce the adhesion force of metallic microparticles

Abstract

Achieving precise control over microparticles on solid surfaces is a challenge due to adhesion forces. One effective strategy for reducing these forces is to modify surface properties in ways that minimize interfacial interactions. This thesis investigates how modifying silicon surfaces can reduce the adhesion of PbSn microparticles by addressing three primary contributing forces: van der Waals, electrostatic, and capillary interactions. A range of chemical (HSQ, Teflon, PMMA, Parylene, Au) and physical (KOH etching, black silicon) surface treatments were applied to silicon chips, and their hydrophobicity was quantified using water contact angle measurements. A custom-built vibration-based setup was used to measure the particle detachment probability. The results show that surfaces treated with Teflon and HSQ exhibited the highest detachment rates and lowest adhesion forces, correlating strongly with their high water contact angles. These findings demonstrate that increasing surface hydrophobicity provides a practical route to reduce microparticle adhesion on silicon substrates.