We have performed a series of atomic simulations, from which the chemical–mechanical relationship of the amorphous/porous silica based low-dielectric (low-k) material (SiOC:H) is obtained. The mechanical stiffness of the low-k material is a critical issue for the reliability performance of IC backend structures. Due to the amorphous nature of the low-k material, a molecular structure model is required, and we present an algorithm to generate such models. In order to understand the variation in the mechanical stiffness and density resulting from modifications to the chemical configuration, sensitivity analyses have been performed using the molecular dynamics (MD) method. Moreover, a fitting equation, based on homogenization theory, is used to represent the MD simulation results in terms of the mean characteristics of the chemical configuration. The trends indicated by the simulation results exhibit good agreement with experimental results. In addition, the simulation result shows the Young’s modulus of the SiOC:H is dominated by the concentration of basicbuilding blocks Q and T, whereas the density is influenced by all the basic building blocks.