Simulation study of organosilicon coating of a spherical nanoparticle immersed in a low-pressure HMDSO/O₂ plasma

Abstract

Using numerical simulations of the multi-fluid equations along with a surface model, the deposition of thin organosilicon films on a spherical nanoparticle immersed in a low-pressure HMDSO/O2 plasma is studied. The effects of variation in the O2 fraction, electron temperature, gas pressure, and the processing temperature on the incident fluxes of the film precursors, the deposition rate, and film thickness, as well as on the relative concentrations of the silicon, oxygen, and carbon in the film structure are investigated. The results revealed that the deposition dynamics is dominated by the SiOC3H9 radical, produced mainly by the electron impact dissociation of the HMDSO molecules. Si 2 OC 5 H 15 + is the most populated ion and plays a prominent role in the deposition process via both direct incorporation and ion-induced stitching. The deposition rate and consequently the film thickness are enhanced with an increase in the electron temperature and the total gas pressure but are reduced with an increase in O2 fraction and the gas temperature. The increase in O2/HMDSO ratio and also the elevation of the electron and gas temperatures lead to an enhanced oxygen/carbon ratio in the film structure, an indication of a high degree of cross-linking. As the pressure rises, the oxygen content of the film increases initially while the carbon content declines, but the reverse is true at higher pressures, due to less effective fragmentation.