Application of scatterometric porosimetry to characterize porous ultra low-k patterned layers

Porous materials such as ultra low-k dielectrics are commonly used in micro and nano technologies. Since porosity leads to an increased sensitivity of the material to etching and post-etching plasma processes, porosity, pore size and surface modifications need to be assessed during material integration. In this work, the recently developed Scatterometric Porosimetry technique using a porosimetry acquisition coupled with a scatterometric analysis is applied to measure the properties of porous patterned layers. Measurements are performed on specially fabricated gratings after exposure to different plasma treatments. A side-by-side comparison between Ellipsometric Porosimetry and Scatterometric Porosimetry is carried out on different plasma-treated samples and shows a different impact of the plasma processes on patterned materials compared with blanket films. These results highlight the interest of Scatterometric Porosimetry to characterize sidewall damage after each step of the process. It also appears as a good complementary technique to Ellipsometric Porosimetry which only allows quantitative measurements on continuous layers.