Application of SiO2 aerogel film with low dielectric constant to intermetal dielectrics

SiO2 aerogel film was characterized from its structural and chemical viewpoints. High porosity of material was measured and compared to thermally grown SiO2 film by Rutherford backscattering spectrometer (RBS). Porous film nature was re-evaluated as enhanced etch rate with high density CHF3-plasma. Detailed observation of microstructure revealed that constituent particles of which the size is in the diameter range of 10-30 nm are cross-linked to build up the skeletal network. Large interior surface coverage, such as alkoxyl group and hydroxyl group were investigated using X-ray photoelectron spectroscopy (XPS) and Fourier transformed infrared spectroscopy (FT-IR) for their chemical states. The improved electrical properties of SiO2 aerogel after annealing at 450 degrees C were interrelated with the thermal evolution of these surface species, where surface alkoxyl plays the dominant role over surface hydroxyl. Furthermore, good gap-filling and planarization ability on 0.8 mu m line and space trench as other requirements for intermetal dielectric application was demonstrated. (C) 1997 Elsevier Science S.A.