With the increase in computational costs driven by the use of artificial intelligence, enhancing the performance of semiconductor systems while improving efficiency has become an inevitable challenge. Due to the fine pitch limits of micro bumps, bumpless Cu-Cu bonding is emerging as the next-generation core technology. This study aims to analyze the effects of individual temperature and pressure on both large- and local-scale behaviors of material in the Cu-Cu bonding process with experiments and numerical analysis. The motivation of this study is to compensate the deficiencies in reported studies on process optimization, particularly the lack of exploration of the separated effects of temperature and pressure on large- and local-scale Cu-Cu bonding. Furthermore, reports on the thermodynamic modeling of Cu-Cu bonding behavior are not sufficient, making it challenging to find suitable models. Bonding experiments were performed by independently controlling the temperature and pressure using blank Cu films treated by precise chemical mechanical polishing (CMP) processes. The large-scale bonded area under each condition was measured, and transmission electron microscope (TEM) images were captured to observe the patterns of local void formation under various temperature and pressure conditions. In the experiments, it was observed that the temperature increase had a greater impact on the bonded area at a larger scale than the increase in pressure. However, for nanoscale-local voids, an increase in pressure had a more dominant effect. To discuss the experimental results, a thermodynamic modeling framework that considers coupled heat-induced deformation, plastic deformation, and volumetric changes caused by material flux was proposed. The proposed model has been implemented in the user-defined material subroutine (UMAT) of the ABAQUS program for finite element (FE) analysis. Numerical analysis using the proposed model captures the experimental data well. In large-scale simulations, temperature conditions have a significant impact, with plastic deformation being the primary mode of deformation, while the pressure conditions dominate the material flux, making substantial contributions to reducing voids at local-scale. To achieve complete closure of the void, the simulation demonstrated that maintaining a sufficient pressure gradient until the complete closure is required. The study findings provide an explicit understanding of how the temperature and pressure conditions differently affect large-scale bonding and local voids for semiconductor package manufacturing.

中文翻译：

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热力学建模框架，对先进半导体封装的 Cu-Cu 键合界面中的大尺寸键合区域和局部空隙进行实验研究


随着人工智能的使用推动计算成本的增加，在提高效率的同时增强半导体系统的性能已成为不可避免的挑战。由于微凸块的细间距限制，无凸块铜-铜键合正在成为下一代核心技术。本研究旨在通过实验和数值分析来分析铜-铜键合过程中各个温度和压力对材料大尺度和局部尺度行为的影响。本研究的目的是为了弥补工艺优化报道研究的不足，特别是缺乏对温度和压力对大尺度和局部铜-铜键合的单独影响的探索。此外，有关铜-铜键合行为热力学模型的报道并不充分，因此寻找合适的模型具有挑战性。使用经过精密化学机械抛光（CMP）工艺处理的空白铜膜，通过独立控制温度和压力来进行键合实验。测量每种条件下的大尺寸粘合面积，并捕获透射电子显微镜（TEM）图像以观察各种温度和压力条件下局部空隙形成的模式。在实验中，观察到温度升高对粘合面积的影响比压力升高的影响更大。然而，对于纳米级局部空隙，压力的增加具有更显着的影响。为了讨论实验结果，提出了一个考虑耦合热致变形、塑性变形和材料通量引起的体积变化的热力学建模框架。 所提出的模型已在 ABAQUS 有限元 (FE) 分析程序的用户定义材料子程序 (UMAT) 中实现。使用所提出的模型进行的数值分析很好地捕获了实验数据。在大规模模拟中，温度条件具有显着影响，塑性变形是主要的变形模式，而压力条件主导材料通量，对减少局部尺度的空隙做出了重大贡献。为了实现空隙的完全闭合，模拟表明需要保持足够的压力梯度直到完全闭合。研究结果提供了对温度和压力条件如何不同地影响半导体封装制造的大规模键合和局部空隙的明确理解。