How to evaluate surface free energies of dense and ultra low-κ dielectrics in pattern structures

A method to evaluate the surface free energy in pattern structure, of chemical vapor deposited dense and ultra low-@k (ULK) SiOCH dielectric films, is presented. Therefore dense and ultra low-@k films were treated by different post ash plasma processes. This films were characterized using Auger electron spectroscopy, atomic force microscopy and contact angle measurements. For both material systems a correlation between the amount of surface near carbon and the surface free energy was found, independent on the plasma chemistry used. The range of the surface roughness is very small and does not have a strong impact on the surface free energy. The correlation model can be applied for pattern structures. After measuring the carbon concentration at the side walls by methods like TEM-EELS or other the model provides the polar and dispersive part of the surface free energy. Having the surface free energy, contact angle of different liquids on or in pattern structures can be calculated. Hence, the wetting behavior and the probability of pattern collapse can be predicted, which is essential to select an appropriate chemical for cleaning and other wet chemical based processes.