Fine Pitch High Density CoWoS-R Package with 1.4/1.4um RDL Lines and 3um via CD

Die-to-die and die-to-HBM fine pitch RDL interconnects are critical to high performance computing (HPC) packaging technology. CoWoS-R is a RDL interposer-based packaging platform, which exhibits low RC interconnect with good signal isolation and design scalability. The technology is currently in production for heterogeneous chiplet/HBM integration with high assembly yields. Packages with large 5.5X CoWoS-R interposer (4 SOC and 12 HBMs) on substrate were built. The RDL lines are scaled from 2 / 2 um to 1.4 / 1.4 um. The vertical via CD is also reduced from 8 um to 3 um. The line density in this large package is significantly increased from 1100 lines /mm to more than 2200 lines /mm. Such a high die-to-die interconnect density can support high speed UCIe, and HBM. The number of total RDL layers can also be reduced for cost reduction purpose. We demonstrate good yields from viachain continuity, comb/meander Rs and leakage current of these fine pitch RDL and via interconnects. The eye diagram width of different fine line L/S(1.4,1.6,1.8,2.0 um) for different line speed (8 Gbps, 10 Gbps) are reported under HBM 36.5 mm length. The suitable fine line by different application should be well chosen based on the line length and line speed. Stress modeling is used to evaluate and mitigate the risk assessment for fine RDL line and small via stress on D2D and D2H area. This reliability of this large package will be presented in this paper.