Nanomechanical Characterization and Metrology for Low-k and ULK Materials

The dielectric constant of dielectric films used in on-chip interconnect stacks of microelectronic products is controlled by the deposited material for low-k and by the incorporation of porosity/voids for ultra-low-k (ULK) materials. The porosity has a significant and direct influence on the mechanical and interfacial properties of these materials. Pore volume fraction and spatial distribution have a detrimental impact on the material stiffness and fracture toughness, film adhesion, sensitivity to CMP and device mechanical reliability during other processing steps. The nanomechanical testing of low-k films - namely nanoindentation and nanoscratch measurements - allows an indirect characterization of the porosity of a ULK film. These tests can resolve variations with nanometer scale spatial resolution as well as changes of porosity of the material as a function of film thickness, all of which significantly impact the mechanical reliability of the device.