Thermal Desorption and Infrared Studies of Sol‐Gel Derived SiO2 Coatings on Si Wafers

Abstract

We investigated thin sol‐gel derived layers by transmission infrared spectroscopy and temperature‐programmed desorption to get information about the influence of different alkoxide mixtures used in the annealing process and especially on the thermal stability of these films, deposited on Si wafers by the spin‐on process. Using only tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS), respectively, the thus formed pure films show cracks already after annealing at ca. 393 K under air. If TMOS is partly substituted by organically modified alkoxysilanes (ca. 30 volume percent of the total alkoxide amount), the temperature of crack formation increases and depends on the thermal stability of included organic groups. In some cases (use of alkoxysilanes modified with methyl or phenyl groups) even after thermal degradation of the organic components the sol‐gel coating remains crack‐free. In addition from the infrared and tpd results some further conclusions can be drawn concerning the densification process of the different sol‐gel layers with increasing temperature.