Impact of the CMP Process on the Multilevel Stack Mechanical Reliability

The Chemical-Mechanical Polishing (CMP) process is still challenging for the semiconductor industry: during this key step, decohesion/adhesion fracture often occurs. The authors have developed a specific methodology in order to estimate this potential risk. This methodology uses finite element simulations in conjunction with a post-treatment computing the Energy Release Rate (ERR) which is related to the risk of delamination To perform the ERR calculation, the Virtual Crack Closure Technique (VCCT) was implemented. This methodology was used for ULK/Cu integration and was validated through experiments. The impact of the process on the wafer residual stress was exhibit. From the fracture point of view, the authors confirm the delamination increases with ULK levels and with lower dielectric elastic modulus.