To further reduce interconnect delay and enable higher device speeds, especially as the critical dimensions are lowered below 0.13µm, the interlevel metal insulator material with dielectric constant as low as 2.0 is desired. Porous materials, which lower the dielectric constant as a result of mixing air with the solid phase, are potential candidates to meet the low dielectric constant objective. Current research is focused on the material characterization, but little attention has been paid to its etching characteristics, although they are critical for process integration. In this research, we have measured etching rates of both porous low-k and low-k (OSG) as functions of ion bombardment energy, ion impinging angle with various fluorocarbon plasma beams, which are necessary for profile evolution modeling of porous low-k etching in inductively coupled plasma. In this work, ions and neutrals are extracted directly from plasma to the main chamber evacuated by a cryo-pump. Surface reaction is studied by measuring etching rate with an ex-situ spectroscopic ellipsometer. At the same time, ion and neutral composition of the plasma is determined with mass spectrometer. And surface composition is analyzed by an X-ray photoelectron spectroscopy. The possible reasons attributing to the difference of the etching behavior between porous low-k and low-k dielectric films has been studied.