Investigation of mechanical properties of black diamond tm (low-K) thin films for Cu/low-k interconnect applications

The mechanical strength of the low-k dielectric thin films plays vital role in deciding the integrity and reliability of the interconnect structures and Cu/low-k packages. Present study focuses on the thickness dependence of mechanical behavior of BD (low-k, Black Diamondtrade) thin films of four different thicknesses, 100, 300, 500 and 700 nm. Nanoindentation and nanoscratch tests have been carried out on all samples using the Nano Indenterreg XP (MTS Corp., USA) system. Nanoindentation experiments with CSM (continuous stiffness measurement) attachment have been performed to assess the hardness (H) and elastic modulus (E) properties. The adhesion/cohesion strength of BD films is measured by using nanoscratch ramp loading technique and reported in terms of the critical load (Lc). Hardness and elastic modulus are found to vary with the BD film thickness (100-700 nm), in the range of 2.02-1.78 and 16.48-9.93 GPa respectively. The critical load (Lc) of the BD-100 nm film could not be determined and mainly expected due to limited resolution of the equipment. The critical loads for BD films (300-700 nm) are in the range of 13.02-18.52 mN