Nondestructive in situ characterization of molecular structures at the surface and buried interface of silicon-supported low-k dielectric films.

As low-k dielectric/copper interconnects continue to scale down in size, the interfaces of low-k dielectric materials will increasingly determine the structure and properties of the materials. We report an in situ nondestructive characterization method to characterize the molecular structure at the surface and buried interface of silicon-supported low-k dielectric thin films using interface sensitive infrared-visible sum frequency generation vibrational spectroscopy (SFG). Film thickness-dependent reflected SFG signals were observed, which were explained by multiple reflections of the input and SFG beams within the low-k film. The effect of multiple reflections on the SFG signal was determined by incorporating thin-film interference into the local field factors at the low-k/air and Si/low-k interfaces. Simulated thickness-dependent SFG spectra were then used to deduce the relative contributions of the low-k/air and low-k/Si interfaces to the detected SFG signal. The nonlinear susceptibilities at each interface, which are directly related to the interfacial molecular structure, were then deduced from the isolated interfacial contributions to the detected SFG signal. The method developed here is general and demonstrates that SFG measurements can be integrated into other modern analytical and microfabrication methods that utilize silicon-based substrates. Therefore, the molecular structure at the surface and buried interface of thin polymer or organic films deposited on silicon substrates can be measured in the same experimental geometry used to measure many optical, electrical, and mechanical properties.

Toughening thin-film structures with ceramic-like amorphous silicon carbide films.

A significant improvement of adhesion in thin-film structures is demonstrated using embedded ceramic-like amorphous silicon carbide films (a-SiC:H films). a-SiC:H films exhibit plasticity at the nanoscale and outstanding chemical and thermal stability unlike most materials. The multi-functionality and the ease of processing of the films have potential to offer a new toughening strategy for reliability of nanoscale device structures.

Tunable plasticity in amorphous silicon carbide films.

Plasticity plays a crucial role in the mechanical behavior of engineering materials. For instance, energy dissipation during plastic deformation is vital to the sufficient fracture resistance of engineering materials. Thus, the lack of plasticity in brittle hybrid organic-inorganic glasses (hybrid glasses) often results in a low fracture resistance and has been a significant challenge for their integration and applications. Here, we demonstrate that hydrogenated amorphous silicon carbide films, a class of hybrid glasses, can exhibit a plasticity that is even tunable by controlling their molecular structure and thereby leads to an increased and adjustable fracture resistance in the films. We decouple the plasticity contribution from the fracture resistance of the films by estimating the "work-of-fracture" using a mean-field approach, which provides some insight into a potential connection between the onset of plasticity in the films and the well-known rigidity percolation threshold.