Effects of copper CMP and post clean process on VRDB and TDDB at 28nm and advanced technology node

Optimization of the polishing and cleaning steps during the copper chemical mechanical polishing (Cu CMP) process can be accomplished by modification of Cu trench profile, control of Cu surface roughness, and reduction of residual Cu ions on the ultra-low k (ULK) surface. For the tuning of the polishing process, the optimized profile will improve the sheet resistance (Rs) and TDDB (time-dependent dielectric breakdown). The cleaning effectiveness would be influenced by the clean chemicals and clean process. The correlation between cleaning effectiveness and voltage ramp dielectric breakdown (VRDB) was investigated. In addition, inductively coupled plasma mass spectrometry (ICP-MS) was found to be a useful tool for the evaluation of post cleaning performance.