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 UV range was measured by nitrogen purged UV ellipsometry. It is shown that im- provement 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).