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Articles you may be interested inUnderstanding of the development of in-plane residual stress in sol-gel-derived metal oxide thin films Effects of deposition temperature on the mechanical and physical properties of silicon nitride thin films J. Appl. Phys. 98, 044904 (2005); 10.1063/1.2006972 Skeletal silica characterization in porous-silica low-dielectric-constant films by infrared spectroscopic ellipsometry J. Appl. Phys. 97, 113504 (2005); 10.1063/1.1903108Effect of sol rheology on the uniformity of spin-on silica xerogel filmsThe biaxial modulus, coefficient of thermal expansion, and crack energy release rate of sol-gel derived silica, xerogel, films are presented. Using stress versus temperature measurements for xerogel on Si and quartz substrates, the biaxial modulus and linear thermal expansion coefficient of the film were determined. The film thickness at the onset of cracking and the corresponding stress were also found. For the critical thickness sample, the cracks initiated in the xerogel film and propagated into the Si substrate. The depth of the cracks in the substrate was roughly equal to the thickness of the film. From these data, the crack energy release rate for steady state channeling in the film was estimated; it was found to be roughly five times 2␥ s , where ␥ s is the reported surface energy of the film. This is an indication of a plastic zone at the crack tip.

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An analysis of the cracking behavior of sol–gel derived silica, “xerogel,” films on silicon substrates is presented. At the onset of film cracking, xerogel films on 〈100〉 Si substrates show a crosshatched crack pattern, while such films on 〈111〉 Si substrates show a random pattern. This is explained by the fact that for an isotropic film the critical film thickness for cracking decreases for increasing substrate compliance. For a 〈100〉 Si wafer, the directions of highest compliance in the plane of the wafer are in the 〈100〉 directions, which lead to cracks in the film parallel to them. A 〈111〉 Si substrate is isotropic in the plane of the wafer and, hence, there is no preferred direction for film cracking. A random pattern is the result.

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