Mechanical Properties of Low-k Dielectric Deposited on Subtractively Patterned Cu Lines for Advanced Interconnects

Mechanical properties of low-k dielectrics deposited on a surface with patterned metal (Cu) lines are evaluated by using atomic force microscopy (AFM) in the PeakForce quantitative mapping (PFQNM) mode. It is shown that Young’s modulus (YM) of completely cured low-k films depends on the position in the structure. The Young’s modulus decreases with reduction of intermetal gap, and it is related to the reduced efficiency of curing. Significant reduction of YM is observed in the areas close to interface between the metal and low-k. The possible reason is bad adhesion between the low-k film and barrier layers and the reduction of effective network connectivity of silicon atoms.