Multi-solvent ellipsometric porosimetry analysis of plasma-treated porous SiOCH films

Porous ultra low-k (ULK) dielectrics are used to reduce resistance–capacitance delay for advanced complementary metal oxide semiconductor interconnects. Since the porosity leads to an increased sensitivity of the material to plasma processes (etching and post-etching plasmas), dedicated characterization techniques are needed to assess the ULK properties during its integration. This study shows that ellipsometric porosimetry, employed with an appropriate multi-solvent protocol, can be effectively used to characterize different plasma-treated porous SiOCH (p-SiOCH) films in terms of porosity, pore sealing and hydrophobicity. It was found that after exposure to fluorocarbon, NH3, H2, CH4 or O2 based plasmas the p-SiOCH surface is modified leading to moisture uptake. According to the plasma, the solvent adsorption is also modified due to a densification of the surface. In that case solvent adsorption measurements were performed in a kinetic mode to quantify the plasma-sealing effect.