Stress and Slurry Chemistry Effects on CMP Damage of Ultra-Low-k Dielectrics

The yield and reliability of the next generation Cu/low-k interconnects depends critically on the control of damage in the form of crack growth in ultra-low-k (ULK) dielectrics. The ULK dielectrics are mechanically fragile and susceptible to environmentally accelerated cracking in reactive aqueous environments. Nevertheless, during chemical mechanical planarization (CMP) and post-CMP cleaning these extremely brittle thin-film structures are subjected to mechanical loads in the presence of harsh aqueous solutions. We demonstrate that both process stress and chemistry are crucial for the rate of damage evolution during CMP. Small changes in CMP slurry chemistry and surfactant additions can have a dramatic effect on damage processes and associated CMP yield. These are crucial aspects for the reliable integration of ultra-low-k materials at next technology nodes.