GOALI: Measurement & Modeling of Heterogeneous Nanoscale Deformation of Copper-Polyimide High Density Interconnect Structures Subjected to Thermal Cycling

基于cu -聚酰亚胺体系的粗高密度互连（HDI）结构相对于Al-SiO2体系表现出了信号传播速率的提高。然而，在加工过程中，面外热膨胀系数的大失配会产生很高的界面应力，这可能会对结构的可靠性产生不利影响。随着接线级别的增加，这个问题将变得更加严重。最近的实验证据表明，聚酰亚胺的弹性性能和热膨胀是1 (m及以下宽度的结构尺寸的函数。另外的实验证据表明，这些结构中的Cu的非弹性变形局限于晶界和Cu与聚酰亚胺之间的界面。此外，在相关温度范围内，位错滑动引起的塑性变形可以忽略不计。由于特征尺寸在Cu晶粒尺寸的量级上，基于非弹性变形连续模型的有限元模型将不能准确描述这些HDI结构中的应力。所提出的分析和实验计划的目标是开发和评估基于这些结构中扩散输运的非弹性非均匀变形模型的策略。具体来说，非弹性变形将局限于晶界和双材料界面。界面和晶界本构模型将以蠕变和晶界滑动机理为基础。晶粒内部和聚酰亚胺中的变形将被建模为线性弹性（具有与温度相关的弹性常数和热膨胀系数）。热段扫描探针显微镜将用于测量界面和晶界滑动的量和速率作为温度的函数。测量材料在晶界和界面处的堆积量将用于量化电缆蠕变机制的材料传输速率。第二个相关目标是制定策略，以测量用于定义导体线路图案的蚀刻所造成的损害所造成的聚酰亚胺的程度和性能变化。减小HDI结构中特征尺寸的趋势要求制定策略来模拟热机械变形，考虑到变形的非均质性，并认识到扩散输运的变形对纳米结构具有一级意义。了解这些影响并记录它们的大小将对整个微电子工业具有广泛的意义。＊＊＊

9631319 Gross High density interconnect (HDI) structures based on the Cu-polyimide system have exhibited improvements in signal propagation rate relative to the Al-SiO2 system. However, the large mismatch in out-of-plane thermal expansion coefficients generates high interfacial stresses during processing that may adversely affect the reliability of the structure. This problem will become more severe as the number of wiring levels increases. Recent experimental evidence has shown that the elastic properties and thermal expansion of the polyimides are a function of structure size for 1 (m widths and below. Additional experimental evidence suggests that the inelastic deformation of the Cu in these structures is localized on grain boundaries and at the interface between the Cu and the polyimide. Furthermore, plastic deformation by dislocation glide has been shown to be negligible for the relevant temperature range. Since the feature size is on the order of the Cu grain size, finite element models based on continuum models of inelastic deformation will not accurately describe the stresses in these HDI structures. The goal of the proposed analytical and experimental program is to develop and evaluate strategies to model heterogeneous, inelastic deformation based on diffusive transport in these structures. Specifically, inelastic deformation will be confined to the grain boundaries and bimaterial interfaces. The interface and grain boundary constitutive models will be based on the mechanisms of Coble creep and grain boundary sliding. Deformation in the grain interiors and in the polyimide will be modeled as linearly elastic (with temperature dependent elastic constants and coefficients of thermal expansion). A hot stage scanning probe microscope will be used to measure the amount and rate of interface and grain boundary sliding as a function of temperature. Measurement of the buildup of material at grain boundaries and interfaces will be used to quantify rates of material transport for the Coble creep mechanism. A second, related goal is to develop strategies to measure the extent and change of properties of the polyimides caused by damage from the etch used to define the pattern for the conductor lines. The trend toward reducing the size of features in HDI structures requires the development of strategies to model thermomechanical deformation that take into account the heterogeneous nature of deformation and recognize that deformation by diffusive transport will be of first order significance for nanostructures. Understanding these effects and documenting their magnitude will have broad significance to the entire microelectronics industry. ***