Heat treatment of spun-on acid-catalyzed sol-gel silica films

Si02 films, formed by spin coating acid-catalyzed TEOS-based sol-gel on Si substrates, were annealed at 300–1000 °C and analyzed using ellipsometry, FTIR, and in situ stress measurements. Film porosity ranged from an average of 28% before annealing to 7% after annealing 3 h at 1000 °C. Below ^800 °C, water and silanol removal caused a decrease in refractive index and increase in the in-plane tensile stress. Infrared spectra indicated compressive strain normal to the plane, however. Above =800 °C, further densification and structural relaxation occurred. Exposure to H20 also caused relaxation after annealing, as the most compressed Si-O-Si units reacted preferentially with moisture. © 1994, Materials Research Society. All rights reserved.