Spin-on glass organosilicate films are promising Ultra Low-ĸ (ULK) interlevel dielectric candidates in which porosity can be created by incorporating thermally labile porogens. The as-deposited film (called the hybrid film) consists of a methylsilsesquioxane (MSQ) matrix and an organic porogen. The standard porogen removal step consists of a 450°C thermal annealing. However, it leaves polymeric residues suspected to cause an incomplete matrix crosslinking and, consequently, to be detrimental to the porous film's electrical and mechanical properties. In this work, a supercritical fluid (SCF) treatment, performed on a 200 mm tool, was added before the thermal annealing with the intent of improving the dielectric properties. Electrical and mechanical properties were greatly enhanced: the dielectric constant was reduced from 2.5 to 2.1 and the Young's modulus was increased from 2 GPa to 3 GPa. Porogen residue removal and cross-linking improvements were investigated by Fourier Transform Infrared (FTIR) spectroscopy in transmission and multiple internal reflection (MIR) mode.