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In this work, a comprehensive analysis and optimization method of electrical and thermal characteristics in 2.5-D integrated circuits (ICs) is performed, including rapid heat distribution modeling, integrated voltage regulator (IVR) chip modeling, and power delivery network (PDN) modeling. Based on the proposed method, chiplet placement, decoupling placement, and IVR parameter settings that compromise the total PDN impedance, IVR impedance, and thermal distribution characteristics can be obtained. First, a rapid thermal analysis method for multiple heat sources is proposed by integrating the equivalent thermal resistance method and commercial tools. The thermal method significantly improves the computational efficiency and reduces the memory usage. Then, we analyze the electrical characteristics of a typical low dropout (LDO) and model the complete 2.5-D PDN, including interposers, chiplets, IVRs, through-silicon vias (TSVs), bumps, decoupling capacitors, and other components. The electrical and thermal problems in the 2.5-D system are formulated and a Metropolis rule-based algorithm is used to derive optimal solutions. Finally, the optimal placement schemes and parameter settings are iterated under different constraints. This method allows for the adjustment of target impedance, noise current, thermal limit, and other constraints based on varying practical situations. In the time-domain analysis, it can be found that the capacitance value is reduced while maintaining the power supply performance. With high accuracy in thermal and electrical modeling, this work provides an in-depth reference for the co-design of chiplet-based 2.5-D ICs.

The utilization of modular chiplets in interposer-based 2.5-D heterogeneous systems simplifies fabrication and design, however, it also introduces significant noise challenges. This article presents a collaborative jitter-aware optimization in 2.5-D integrated circuits (ICs), incorporating power supply induced jitter (PSIJ), system impedance, target impedance, and decoupling capacitors, based on the hybrid precomputation and prestorage/duplicate removal-nondominated sorting differential evolution (PCPS/DR-NSDE) algorithm. An automatic channel model algorithm and a uniform decoupling capacitor placement strategy are proposed to improve the design efficiency. Then, the system transfer impedance, simultaneous switch current, sensitivity function, and amplification factor are individually modeled, leading to the assembly and verification of the final PSIJ in the 2.5-D system. A precomputation and prestorage (PCPS) strategy is proposed to handle high-time-consuming modules in the objective function and a duplicate removal (DR) operation is added to improve algorithm performance. The proposed PCPS/DR-NSDE is faster than traditional algorithms and has optimal hypervolume and coverage-metric (C-metric) indicators. The procedures for further obtaining desired solutions in the Pareto front are discussed. The impact of practical constraints and target impedance is also analyzed. This work provides a collaborative optimization and analysis of jitter, noise, and impedance in 2.5-D systems.

Joint homogenization during transition metal carbides ceramic bonding has attracted much attention as a technique to increase the service temperature and relieve the residual stress for various high-temperature applications. In this work, homogeneous joints of ZrC0.85ceramic were obtained by diffusion bonding using single Nb and multiple Ti/Nb/Ti as the interlayer. The effect of interlayer composition, bonding temperature and holding time on the microstructure of the joints was investigated. The effect of Nb and Ti on the composition homogeneity and the formation of Kirkendall voids in the ZrC0.85joints was also discussed. When using single Nb as the interlayer, the homogenization of the joints can be achieved at a bonding temperature of ∼1500 °C and holding for 1 h and no Kirkendall voids were observed when further increasing the bonding temperature to 1600 °C because of the good mutual solubility of NbCxand ZrCxand the relative moderate diffusion rate of Nb. However, severe Kirkendall effects were observed at a higher temperature of 1700 °C, which would deteriorate the high-temperature performance of the joints. The adoption of Ti/Nb/Ti further minished the diffusion rate difference of the interfacial elements through the formation of TiCxphase. As a result, only a few Kirkendall voids were formed at 1700 °C. Nano-hardness of the resultant homogeneous joints was comparable to that of the ZrC0.85ceramic due to their similar composition. This study shows that active diffusion bonding based on interlayer design for homogeneous joints could pave a new way to join transition metal carbides.