Superior mechanical properties of dense and porous organic/inorganic hybrid thin films

Abstract

The intrinsic mechanical properties of a given material strongly depend upon its chemical nature. Organic materials tend to be soft, but tough, while inorganic materials are hard, often brittle and are prone to fracture. The latter characteristic is even more exacerbated in porous materials. This presents a major hurdle in trying to integrate porous organosilicates as insulating layers in future electronic devices. In this presentation, we demonstrate that significantly tougher organosilicate glass thin-films prepared by sol-gel process can be obtained by introducing carbon-bridging units between silicon atoms present in the organosilicate network. Surprisingly, higher fracture energy values of 17 J/m2 were measured for the new material as compared to those for dense silicon dioxide (10J/m2). Implications are that mechanical properties apparently fall somewhere in between those of conventional glasses and organic polymers. In addition, it was observed that the Young's modulus follows a linear decay when porosity is introduced, a unique property when compared to traditional organosilicates which exhibit exponential decay. As a result, crack resistant films were obtained at high levels of porosity, making this class of materials an excellent candidate for low-k, dielectric applications.