LAUSR

System-level thermal management of heterogeneously integrated HBM–graphics processing unit (GPU) module with step height variance is analyzed in this article. Heterogeneous integration of high-powered chiplets with different functionalities and die sizes motivates the development of advanced cooling solutions that are compatible with multidie configurations. By exploiting computational fluid dynamics (CFD)–heat transfer (HT) analysis, we propose top-side single-phase microfluidic cooling solutions that compensate for multidie thickness mismatch, including a flat-microchannel pin-finned heat sink (F-MPFHS) with structural silicon and a backward-facing step microchannel pin-finned heat sink (BFS-MPFHS). The thermal performances are benchmarked with a conventional forced air-cooled heat sink with structural silicon. The HBM–GPU module is modeled up to 35 W from the HBM and 2000 W from the GPU. Thermal–hydraulic indexes, including thermal resistance, pressure drop, and coefficient of performance (COP), are evaluated. The temperature of the HBM–GPU can be maintained below 387 K at the highest flow rate of 0.15 L/min with a pumping power of 169 and 117 mW for F-MPFHS and BFS-MPFHS, respectively. A 45% higher COP is calculated for BFS-MPFHS with a step height of $235~\mu $ m, owing to a 31% lower pressure drop with a 7.4% lower thermal resistance compared with F-MPFHS. A performance–cost tradeoff relationship between the design solutions is revealed, as BFS-MPFHS requires a relatively complex fabrication process despite its higher COP. The thermal impacts of GPU power scaling, the number of DRAM stacks (eight-, 12-, and 16-stack), and step height variations are further investigated.