Dishing study of polyimide CMP process

Polyimide is the promising material as inter-dielectric due to its outstanding properties. This paper reports polyimide CMP process and studies the dishing performance over different structures on different wafer locations. 8 inch silicon test wafers were patterned with different structures after SiO2 deposition, etching and polyimide coating. Then CMP polished wafers by changing recipe parameters to get variable dishing performance. Final results showed better and more stable dishing performance with better uniformity when T.R. pressure = 150 and slurry dilution = 50%. And narrower structures have much lower dishing.