Analysis of the residual stresses, the biaxial modulus, and the interfacial fracture energy of low- k dielectric thin films

A method was developed for the evaluation of the residual stresses and the biaxial modulus of thin films and the interfacial fracture energy of the interface between the thin film and the substrate. The "superlayer" method, which consists of depositing a thin metallic film on top of the investigated film, was employed to evaluate all the above mechanical properties. The investigated thin films in this report were 0.5, 1, and 1.5 μm thick coral low- k dielectric films that were deposited on top of Cu and Ta thin films, all on top of (001) silicon wafers. Thinner Ti films of 150, 200, and 250 nm thick were used as the superlayers. These properties were obtained by measuring the radius of curvature of the released or of the delaminated Ti/coral bilayers. Nine bilayers, combined from all the thicknesses mentioned above, were tested. The wide experimental procedure enabled to extract the unknown properties by a special procedure developed for this purpose, and to draw conclusions regarding the accuracy of the results and the effect of layer thickness. Finally, and based on the large experimental data, we recommend on the minimal required tests to evaluate these mechanical properties. With this information, we show that a single mm2 lab on chip is a sufficient area to contain the specimens required for the evaluation of the above-mentioned properties.