The semiconductor industry is turning to 3D integrated circuits (3D ICs) to meet increasing demands for high performance, miniaturization and energy efficiency. By stacking dies into 3D assemblies, we get faster data processing, reduced power consumption and more efficient use of space. For automotive applications, which require highly reliable devices for safety-critical functions, these improvements are invaluable. However, 3D ICs also introduce unique challenges in thermal management—heat generated in these complex stacks can impact electrical behavior, reliability, performance and lifespan. Effective management of these thermal effects is crucial for automotive applications where the chips must operate consistently under diverse and sometimes extreme conditions.
Thermal challenges of 3D ICs in automotive applications
In traditional 2D designs, heat dissipation occurs across a single plane. With 3D ICs, however, heat is generated across multiple active layers, creating thermal gradients and hotspots that can affect device performance, lead to timing errors, increased leakage currents and even device failure (figure 1). The challenge is particularly intense for automotive applications, where components must be reliable across a wide range of operating environments. As a result, precise thermal analysis throughout the 3D IC design process is essential.
The importance of early and continuous thermal analysis
Thermal analysis has traditionally been a post-design step, often limited to package and system levels. For 3D ICs, thermal analysis must occur at the die level and start early in the design process to identify potential hotspots and thermal bottlenecks before they escalate. Early insights allow designers to make strategic adjustments to chiplet placement, power distribution and cooling mechanisms.
During the early stages of package design and floorplanning, designers can use high-level power estimates and simplified models to run thermal feasibility studies. These analyses help identify configurations that could cause thermal problems, letting designers rule out high-risk layouts before committing significant resources. For example, thermal analysis can detect overlapping heat sources in stacked dies or highlight areas that lack adequate cooling paths (figure 2).
As the design process progresses, thermal analysis should be conducted iteratively to ensure the design stays within acceptable thermal limits. By aligning thermal analysis with other verification tasks, like timing and power checks, designers gain a holistic view of the design’s performance and reliability, ensuring they are working toward a robust final product.
Thermal analysis tools: key features and benefits
Thermal analysis tools must offer capabilities to support each stage of the design process, from early planning to final signoff.
1. Early design planning: Use power estimates to explore the thermal impacts of various design choices, such as partitioning options, die assembly and block layouts. Early analysis reduces the risk of expensive rework.
2. Detailed design and implementation: As designs evolve, verify thermal limits against the design's thermal budget. At this stage, power maps provide critical information to capture hotspots accurately.
3. Design signoff: Ensure that all thermal constraints are met before the product is finalized. Designers receive comprehensive feedback on any lingering issues, expediting the signoff process.
4. Integration with package-system analysis: Integrated die-level and package-level thermal models allow for a continuous thermal analysis workflow from die design to final system-level evaluation.
High-fidelity thermal models capture 3D IC assembly details like non-uniform material properties, fine-grained power distributions and the effects of features such as through-silicon vias (TSVs). For example, the Siemens EDA tool, Calibre 3DThermal, incorporates custom 3D solvers for precise, nanometer-scale thermal analysis.
Advanced automation allows designers to manage thermal analysis without requiring deep expertise in thermal engineering. Key automated features include:
1. Optimized gridding: Tools automatically apply finer grids in critical areas to increase resolution while using coarser grids elsewhere for efficiency.
2. Time-step management: In transient analysis, tools automatically adjust time steps to capture transitions precisely.
3. Equivalent thermal properties: Tools apply different bin sizes for critical and non-critical areas, optimizing model complexity while maintaining accuracy.
4. Power map compression: Adaptive binning compresses power maps, improving tool performance.
5. Automated reporting: Tools generate summary reports, highlighting key results for quick and easy review.
Advanced tools also integrate seamlessly with other design tools, providing a unified environment to manage thermal, electrical and mechanical constraints. This integration ensures that thermal considerations are addressed from initial feasibility analysis through final signoff.
The path forward for automotive 3D IC thermal management
As automotive applications grow more complex, effective thermal analysis throughout the 3D IC design process becomes indispensable. Designers who incorporate thermal analysis early and iterate thermal models gain a significant advantage in reducing risks, speeding up design cycles and ensuring long-term reliability. High-quality thermal analysis tools are essential for addressing the multifaceted challenges of 3D ICs in automotive applications, helping engineers deliver safe, efficient devices.
For more on 3D IC thermal analysis, read Conquer 3DIC thermal impacts with Calibre 3DThermal.
