Tian Wenchao, Gao Ran, Gu Lin, Ji Haoyue, Zhou Liming
Hangzhou Institute of Technology, Xidian University, Hangzhou 311231, China.
School of Electro-Mechnical Engineering, Xidian University, Xi'an 710071, China.
Micromachines (Basel). 2023 Jun 15;14(6):1255. doi: 10.3390/mi14061255.
To meet the demands for miniaturization and multi-functional and high-performance electronics applications, the semiconductor industry has shifted its packaging approach to multi-chip vertical stacking. Among the advanced packaging technologies for high-density interconnects, the most persistent factor affecting their reliability is the electromigration (EM) problem on the micro-bump. The operating temperature and the operating current density are the main factors affecting the EM phenomenon. Therefore, when a micro-bump structure is in the electrothermal environment, the EM failure mechanism of the high-density integrated packaging structure must be studied. To investigate the relationship between loading conditions and EM failure time in micro-bump structures, this study established an equivalent model of the vertical stacking structure of fan-out wafer-level packages. Then, the electrothermal interaction theory was used to carry out numerical simulations in an electrothermal environment. Finally, the MTTF equation was invoked, with Sn63Pb37 as the bump material, and the relationship between the operating environment and EM lifetime was investigated. The results showed that the current aggregation was the location where the bump structure was most susceptible to EM failure. The accelerating effect of the temperature on the EM failure time was more obvious at a current density of 3.5 A/cm, which was 27.51% shorter than 4.5 A/cm at the same temperature difference. When the current density exceeded 4.5 A/cm, the change in the failure time was not obvious, and the maximum critical value of the micro-bump failure was 4 A/cm~4.5 A/cm.
为满足对小型化、多功能和高性能电子应用的需求，半导体行业已将其封装方式转向多芯片垂直堆叠。在用于高密度互连的先进封装技术中，影响其可靠性的最持久因素是微凸点上的电迁移（EM）问题。工作温度和工作电流密度是影响电迁移现象的主要因素。因此，当微凸点结构处于电热环境中时，必须研究高密度集成封装结构的电迁移失效机制。为了研究微凸点结构中加载条件与电迁移失效时间之间的关系，本研究建立了扇出型晶圆级封装垂直堆叠结构的等效模型。然后，利用电热相互作用理论在电热环境中进行数值模拟。最后，以Sn63Pb37作为凸点材料，调用平均无故障时间（MTTF）方程，研究了工作环境与电迁移寿命之间的关系。结果表明，电流聚集处是凸点结构最易发生电迁移失效的位置。在电流密度为3.5 A/cm时，温度对电迁移失效时间的加速作用更为明显，在相同温差下比4.5 A/cm时缩短了27.51%。当电流密度超过4.5 A/cm时，失效时间变化不明显，微凸点失效的最大临界值为4 A/cm~4.5 A/cm。
