In present generations of high-performance microelectronic devices, the constantly increasing density and larger-scale integration require closer spacing between interconnect lines and lower dielectric constant (low-k) of the dielectric material in order to reduce the capacitive coupling between the interconnect lines. Ultra-low-k materials in future-generation microelectronic technologies must also satisfy certain integration requirements, such as a minimum mechanical strength, threshold of thermal and electrical breakdown, and suitability for lithographic processing during chip manufacturing. Mechanical strength is particularly important: the dielectric material also is a structural component in the microchip that is required to ensure the structural integrity of the device under the thermomechanical loading conditions characteristic of semiconductor manufacturing processes, chip packaging, and device service. Among new materials for ultra-low-k applications, porous amorphous silicas have significant economical advantages due to their compatibility with current semiconductor manufacturing technologies.

In this presentation, we report results of molecular-dynamics (MD) simulations aiming at a fundamental understanding of the nano-scale mechanisms that control the mechanical behavior of mesoporous amorphous silica film structures and predicting the response of such structures to various mechanical loading conditions. The MD simulations employ a realistic classical potential that includes two-body and three-body interatomic interactions. The normal-density amorphous silica structures are prepared through MD starting from a crystalline beta-cristobalite solid structure and following a thermal processing sequence that includes melting, rapid quenching, and a thermal annealing schedule. We have generated “regular” mesoporous structures through the introduction of a regular array of spherical pores with nanometer-scale diameter by removal of atoms from the normal-density amorphous silica matrix and subsequent thermal annealing at the temperature of interest to ensure proper structural relaxation.

We present a systematic analysis of the mechanical response of these regular mesoporous amorphous silica structures under applied strains within the elastic limit near room temperature based on isostrain MD simulations using large-size computational supercells. The elastic moduli of the mesoporous structures are computed and their structural stability is analyzed under tensile and compressive strains as a function of density and pore diameter. We also analyze the anelastic characteristics of the mechanical behavior of these mesoporous structures based on nanosecond-scale MD simulations of dynamic deformation (i.e., constant strain rate) experiments under both tensile and compressive strains over a range of strain rates from 10⁸ to 10¹⁰ s^-1. Furthermore, we analyze the effects of thermal treatment near the glassy transition temperature of the mesoporous amorphous structures on their structural stability and mechanical strength under compressive strain.