Thermal Cure Study of a Low-<i>k</i> Methyl Silsesquioxane for Intermetal Dielectric Application by FT-IR Spectroscopy

Abstract

In this paper, Fourier transform infrared (FT-IR) spectroscopy is used to study the thermal properties of methyl silsesquioxane (MSQ), an important low-dielectric-constant organic spin-on glass for semiconductor device fabrication. The compositional and structural changes of MSQ with temperature are investigated in detail. The cross-linking process, where the three-dimensional networked structure is formed, is found to start at room temperature, and is almost complete at the typical baking temperature of 250 °C. Further cross-linking occurs during the curing process at 425 °C, and small short-chain clusters can also be driven away at this temperature by sublimation. In this study, we have assigned all the MSQ IR peaks and we have used the long-chain O–Si–O IR peak to calculate the “degree of cross-linking” quantitatively.