Optimal Channel Design for Die-to-Die Interface in Multi-die Integration Applications

To support technical trend of multi-die integration in HPC platform, various die-to-die interface IPs have been introduced for seamless connection between dies with the wide bandwidth. In addition to the conventional channel routed in single medium of Si-interposer or organic substrate, D2D interface through the channel where multiple media are used may also be required depending on the system requirements. This study focuses on analyzing and comparing the bandwidth of D2D interface in various channel configurations including the traditional solutions with a single medium. The entire channel structure consists of a multi-stage channel that connects two interposers with a SOC die and multiple HBM dies in an organic substrate, or two small ABF packages in a large-size, low-cost HDI substrate. In the entire D2D channel with multiple media, impedance mismatching and coupling may occur additionally at the joint balls and the performance degradation of high-speed signal is inevitable, but the performance can be improved through design optimization process. The channel performance with 9 type configurations was assessed and the allowable signaling speed was estimated by the target criteria of eye opening. By each channel configuration, it was suggested which design characteristics are dominant to the signal performance and how the performance can be improved. In conclusion, by comparing and analyzing the signal performance depending on complex design parameters in various channel conditions, we suggested the optimal D2D design solution for multi-die integration, considering target bandwidth and package cost. This approach is expected to be useful to comprehend the performance of multi-stage channel consisting of multiple joint junctions with uneven characteristic impedance.