LegoTherm: Modular and reusable thermal model for chiplet-based heterogeneous integration

Thermal management critically affects the reliability of chiplet-based heterogeneous integrated circuits (ICs) in the post-Moore era. The design process demands hundreds of thermal simulations across varying power distributions, cooling conditions, and structural configurations. Conventional methods based on finite element methods (FEM) and compact thermal model (CTM) lack the flexibility for efficient multi-scenario evaluations and incur prohibitive computational cost when modeling complex vertical stacks with cross-scale interconnects. We propose LegoTherm, a modular thermal modeling framework that decomposes chiplet-based systems into reusable reduced-order components. The framework exploits the inherent hierarchical structure of heterogeneous integration to construct high-fidelity 3D meshes capturing micro-interconnection details through modular discretization, then generates reduced-order modules by aggregating thermally coupled interface ports. This approach preserves critical hotspot accuracy while enabling rapid reassembly for different design scenarios. Evaluated on industrial-scale 2.5D and 3D packaging benchmarks, LegoTherm achieves up to 10.39× speedup compared to COMSOL while maintaining mean relative error below 0.40%. The framework reduces thermal design iteration cycles from weeks to half a day, addressing a critical bottleneck in modern IC design.