Improvements of CMP characteristics using slurry filter and high-spray bar of de-ionized water

As the integrated circuit device size shrinks to smaller dimensions, a chemical mechanical polishing (CMP) process was required for the global planarization of inter-metal dielectric (IMD) layer free of defects. However, as the IMD layer gets thinner, micro-scratches are becoming a major concern. Micro-scratches are generated by agglomerated slurry, solidified and attached slurry in the pipe-lines of the slurry supply system. In order to prevent the agglomerated slurry particles from slurry inflow, we installed a 0.5-μm point-of-use (POU) filter, which is a depth-type filter and has 80% filtering efficiency for the 1.0-μm size particles. Also, a high-spray bar of de-ionized water with high pressure was installed in the CMP equipment. In this paper, we studied the relationship between defect generation and pad counts to understand the exact efficiency of the slurry filter, and to determine the appropriate pad usage. Our experimental results showed that it is impossible to prevent defect-causing particles completely through the depth-type filter. Thus, we suggest that it is necessary to optimize the slurry flow rate and to install a high-spray bar of de-ionized water (DIW) with high pressure, in order to overcome weak points of the POU depth-type filter.