STAMP-2.5D: Structural and Thermal Aware Methodology for Placement in 2.5D Integration

By Varun Darshana Parekh^∗, Zachary Wyatt Hazenstab^∗, Srivatsa Rangachar Srinivasa^†, Krishnendu Chakrabarty^‡, Kai Ni^§, Vijaykrishnan Narayanan^∗
∗ The Pennsylvania State University, USA
^† Intel, Hillsboro, USA
^‡ Arizona State University, USA
^§ University of Notre Dame, USA

Abstract

Chiplet-based architectures and advanced packaging has emerged as transformative approaches in semiconductor design. While conventional physical design for 2.5D heterogeneous systems typically prioritizes wirelength reduction through tight chiplet packing, this strategy creates thermal bottlenecks and intensifies coefficient of thermal expansion (CTE) mismatches, compromising long-term reliability. Addressing these challenges requires holistic consideration of thermal performance, mechanical stress, and interconnect efficiency. We introduce STAMP-2.5D, the first automated floorplanning methodology that simultaneously optimizes these critical factors. Our approach employs finite element analysis to simulate temperature distributions and stress profiles across chiplet configurations while minimizing interconnect wirelength. Experimental results demonstrate that our thermal structural aware automated floorplanning approach reduces overall stress by 11% while maintaining excellent thermal performance with a negligible 0.5% temperature increase and simultaneously reducing total wirelength by 11% compared to temperature-only optimization. Additionally, we conduct an exploratory study on the effects of temperature gradients on structural integrity, providing crucial insights for reliability-conscious chiplet design. STAMP-2.5D establishes a robust platform for navigating critical trade-offs in advanced semiconductor packaging.

Index Terms — Heterogeneous Integration, Automated Floor Planning, Chiplet Architecture, Thermal-Mechanical Evaluation

I. INTRODUCTION

The continuous advancement of semiconductor technology has driven an ever-increasing demand for higher performance, greater functionality, and enhanced integration density in electronic systems. Chiplet-based architectures, particularly 2.5D integration, have emerged as promising solutions in the electronics industry, bridging the gap between chip and package sizes by mounting multiple dies on a single package substrate. This approach enhances capacity and performance by facilitating heterogeneous integration of chiplets with varied functionalities and material properties into unified systems. Advanced packaging technologies, including Through-Silicon- Via (TSV) fabrication methods and multi-level assembly techniques, have further solidified the reliability and affordability of 2.5D packaging.

Recent advancements in chiplet architectures and advanced packaging technologies have revolutionized system design, offering viable pathways to address the slowdown of Moore’s Law. Successful commercial implementations leverage chiplet architecture to integrate 7nm CPU dies with 12nm I/O dies for optimal performance and cost. Recent advances have further demonstrated scalability and efficiency in chipletbased systems using heterogeneous 2.5D packaging techniques for workload-dependent configurations. These innovations have catalyzed the development of diverse integration strategies, leveraging silicon interposers, bridge-chip technology, active interposers, and 3D interconnects. Chiplet integration thus allows for scalable architectures, flexibility in node selection, and significant reuse of off-the-shelf intellectual properties (IPs). However, substantial challenges persist, notably in inter-die communication, mixed-node integration, and thermal management.

Thermal management has become increasingly critical in 2.5D chiplet systems, driven by higher integration densities and power densities in advanced semiconductor nodes. Extensive research efforts employing finite element analysis and computational fluid dynamics have studied thermal behaviors and factors influencing package warpage, die stress, and solder joint reliability. Nevertheless, while thermal considerations have been extensively explored, mechanical stress implications, particularly arising from the mismatch in the Coefficient of Thermal Expansion (CTE) among heterogeneous dies and interposers, remain inadequately investigated.

Thermomechanical stress poses substantial reliability risks in 2.5D packages, warranting integrated consideration alongside thermal and interconnect optimization.

To address these challenges, recent methodologies have started exploring chiplet placement strategies that incorporate thermal considerations. One such approach, TAP-2.5D, strategically inserts spacing between chiplets to jointly optimize thermal performance and wirelength. However, existing methodologies predominantly focus on thermal and interconnect objectives, neglecting a critical component—the mechanical stresses due to thermal expansion mismatches—which significantly affect long-term reliability.

In contrast, this paper presents STAMP-2.5D: Structural and Thermal Aware Methodology for Placement in 2.5D Integration, the first automated placement methodology that holistically integrates thermal performance, mechanical stress, and interconnect wirelength optimizations. Our proposed framework utilizes finite element analysis (FEA) simulations using ANSYS to concurrently evaluate thermal and mechanical stress profiles, enabling effective exploration of critical design trade-offs and ensuring robust reliability in advanced packaging.

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