Effects of deionized water pressure and purified nitrogen gas on the chemical mechanical polishing process

Abstract

The chemical mechanical polishing (CMP) process is widely used for the global planarization of inter-layer dielectric (ILD) for deep sub-micrometer technology. But hot-spots due to partial over-polishing generated in the edges of wafers, have become a major concern. Thus, it is very important to understand the correlation between the ILD-CMP process and various facility factors of the CMP equipment system. With a facility shortage of de-ionized water (DIW) pressure, we introduced an additional purified nitrogen (PN2) gas in the polishing-head-cleaning station to increase the cleaning effect. Our experimental results show that DIW pressure and PN2 gas factors were not related to the removal rate, but edge hot-spots on the patterned wafer had a strong relation with them. We estimated two factors (DIW pressure and PN2 gas) for the improvement of the CMP process. In particular, we obtained a uniform planarity in the patterned wafer and prevented more than 90% of wafer edge over-polishing. Finally, we suggest that the facility factors for an equipment system play an important role in the ILD-CMP process.