Stiffening and hydrophilisation of SOG low‐k material studied by ellipsometric porosimetry, UV ellipsometry and laser‐induced surface acoustic waves

In this paper we evaluate the correlation between UV light absorption of SOG (spin-on glass) low dielectric constant (low-k) films and chemical changes induced by an excimer UV source at several wavelengths: 172 nm, 222 nm, and 308 nm. Low-k absorption in the UXV range was measured by nitrogen purged UV ellipsometry. It is shown that improvement of mechanical properties is accompanied by degradation (hydrophilisation) of low-k films. Changes in hydrophobic properties were evaluated by water-source ellipsometric porosimetry (WEP). The Young's moduli of the films were measured by laser-induced surface acoustic waves (LAwaves).