A new technique, so called "scatterometric porosimetry" (SP) has been developed to improve our knowledge on the properties of porous material patterned structures. None of the existing techniques is able to characterize the porous material structures after patterning. SP is based on the measurement of the refractive index variation of porous material structures (lines and holes) when filled with a solvent (toluene, methanol, and water). This technique is applied to monitor the modifications in low-K dielectric materials (porous SiOCH) after the plasma patterning steps used to form lines and vias in the porous materials in a typical dual damascene CMOS technology process. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3457489]