Process emulation for predicting die shift and wafer warpage in wafer reconstitution
Process emulation for predicting die shift and wafer warpage in wafer reconstitution
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用于预测晶圆重构中芯片移位和晶圆翘曲的工艺仿真
DOI：
10.1109/icept.2017.8046441
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
S. Lee
中科院分区：
文献类型：
--
作者：
C.;Y.C. Liu;K.‐S. Chen;T. Yang;Y.;S. Lee
晶圆重构是将集成电路制造和电子封装之间的工艺发展脱钩的重要缓冲过程。通过这种方法，IC封装可以独立于芯片加工。然而，这样的工艺在成型和固化阶段会带来大量的机械负荷。在没有仔细计划的情况下，经常会报告芯片移位和晶片翘曲过多等故障，这会导致后续处理的问题。在这项工作中，希望通过执行流体模流和固体热机械分析以及必要的材料表征来检查芯片移动和晶片翘曲的关键因素。初步将移模问题归结为流体载荷、热膨胀、模料收缩和粘弹性效应的相互作用。为了更深入地了解，我们建立了简化的流体模型和有限元分析，以模拟整个Recon过程。对于结晶器流动分析，采用了简化的一维粘性流动分析模型。它的目的是找出成型参数与所获得的速度场和压力场之间的关系，以计算可能作用于模具上的引起位移的阻力和剪力。另一方面，在成型后，用有限元方法计算整个固化过程的应力和变形。然后逐步检查可能的模具移动和最终翘曲，以评估每个步骤甚至每个工艺参数的贡献。对简化的二维轴对称模型和三维模型进行了计算和分析。初步分析结果表明，固化过程中的热应力是目前的主导因素。相关参数，如化合物和载体的性质，以及工艺参数，如固化温度和时间可能是主要的控制因素。
Wafer reconstitution is a vital process for serving as a buffer to decouple the processing developments between IC fabrication and electronics packaging. By this approach, the IC packaging is then independent from the chip processing. However, such a process brings numerous mechanical loadings during molding and curing phases. Without carefully planning, failures such as die-shifting and excessive wafer warpages are frequently reported and it induces problems for subsequent processing. In this work, it is desired to examine the key factor of die-shift and wafer warpage by performing both fluidic mold flow and solid thermo-mechanical analyses, as well as essential material characterizations. Preliminarily, the die-shift problem is deduced as interaction of fluid load, thermal expansion, shrinkage of molding compound and viscoelastic effect. To have a deeper insight, simplified fluid model and finite element analyses have been constructed to mimic the entire Recon process. For mold flow analysis, a simplified 1-D viscous flow analytical model is adapted. It aims to find the relationship between the molding parameters and the achieved velocity and pressure fields for calculating the possible drag and shear forces acting on dies for causing shift. On the other hand, after molding, the stress and deformation of the entire curing process is then performed by finite element method. The possible die shift and final warpage are then examined step by step to evaluate the contribution from each step and even each processing parameter. Both simplified 2-D axisymmetric and 3D models are performed and analyzed. The preliminary analysis results indicate that the thermal stress during curing is the current dominating factor. Related parameters such as the properties of compounds and carriers and the process parameters such as the curing temperature and duration could be the major controlling factors.