Research on Improvement of CMP Thickness Uniformity Control on Wafer Edge Defocus Defects

As the shrinkage of the geometry size of the semiconductor, wafer planarization process requirements are getting higher and higher, especially in the back-end Cu Damascus process, the thickness profile control of wafer edge become more and more important. Some wafer far edge defocus defect appears during the development of HLMC 28 nm products. From the analysis of the distributed detection of the thickness of copper film after CMP within the scope of the radius of 130 mm to 147 mm, the thickness of the copper has increased after the first reduce the mutation effect. Is mainly due to the CMP process on the edge of the wafer thickness uniformity control less than optimal. Because of the superposition effect of copper wire process, defocus defect count increases with copper layer increases. This article mainly discusses the causes of the wafer edge defocus defects, and design a series of CMP pressure to improve conditions, by collecting the CMP after copper film thickness and its influence to the layer after photolithography leveling, and eventually track defocus defects to determine the optimal CMP polishing pressure conditions.