HEAT-TREATMENT OF SPUN-ON ACID-CATALYZED SOL-GEL SILICA FILMS

SiO2 films, formed by spin coating acid-catalyzed TEOS-based sol-gel on Si substrates, were annealed at 300-1000-degrees-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-degrees-C. Below almost-equal-to 800-degrees-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 almost-equal-to 800-degrees-C, further densification and structural relaxation occurred. Exposure to H2O also caused relaxation after annealing, as the most compressed Si-O-Si units reacted preferentially with moisture.