Characterization of Nanoscale Defects and Pores

0100009 Gidley提出了一个跨学科的研究计划，结合了著名的正电子湮没寿命谱（帕尔斯）与国家的最先进的正电子束技术的空隙体积灵敏度，以表征缺陷和孔隙在广泛的工程材料，传统的技术是不够的。孔隙率控制是纳米工程新兴领域的一个重要方面。在微电子“低K”介电膜、薄聚合物渗透过滤器和催化膜中引入和工程孔隙率吸引了强烈的研究兴趣。另一方面，防止界面缺陷孔隙率是结构材料如粘合剂、胶粘剂和复合材料中的长期问题。传统的探针受到这些非常薄的膜的无定形性质和孔/缺陷的纳米级尺寸的挑战。帕尔斯已被证明是一个重要的新工具，在表征这种亚微米薄膜系统中的纳米孔隙率。由于先前的NSF-ECS授予光束-帕尔斯在帮助微电子工业开发下一代，低K层间介电薄膜中发挥着重要作用。已经证明了帕尔斯对1-100纳米孔的尺寸和互连性的敏感性。开发了一种用于提取闭孔系统的孔径分布的程序。发现帕尔斯对Cu相互扩散到电介质中敏感，因此也可以测试所需的扩散阻挡层完整性。本建议将扩大这项工作。金属相互扩散和屏障完整性/热稳定性将进行研究，特别注意开发一个标准化的帕尔斯测试程序，要求由Sematech，主要由美国主要的研究财团电子公司。将继续进行交叉校准实验，使用用于表征孔隙度的补充技术，如NIST的小角中子散射（SANS）和IMEC的溶剂吸收椭圆偏振孔隙度测定法。这些研究有助于确定每种技术的独特优势和弱点。该提案的第二个主要推动力将是聚合物薄膜、表面和界面的研究。IBIS的研究建立在以前的工作中，光束PALS被用来研究薄的10微米聚合物薄膜约束在硅晶片上的结构和动力学。发现这种薄膜在硅旁边有一个高度固定的“粘合”层，在表面有一个不受约束的“液体”层。特别注意将集中在界面区域，以确定的敏感性的固定层的粘附失败和分层的发病。如果失效是由于前体纳米空隙聚结成较大的孔，例如，由于疲劳，热应力或腐蚀，深度轮廓的梁PALS应该是一个非常强大的探针，这个故障前的初始阶段，否则是不可见的。具体而言，缺陷空隙的作用，在微电子封装中使用的聚合物胶粘剂和粘合剂的故障将进行研究。此外，亦会进行一项辅助研究，研究化学增幅光阻在紫外光照射下显影时，纳米结构的演变。这项研究计划是建基于密歇根大学物理系与材料科学及工程系之间现有的紧密合作。为了提供关键的指导和明确的重点，PI已经与六家公司、NIST和两个大型工业联盟建立了强有力的合作关系;美国的Sematech和欧洲的IMEC。

0100009GidleyAn interdisciplinary research program is proposed that combines the well-known void-volume sensitivity of positron annihilation lifetime spectroscopy (PALS) with state-of-the-art positron beam technology in order to characterize defects and pores in a wide range of engineering materials where traditional techniques are not adequate. Porosity control is an important aspect of the emerging field of nanoengineering. Introducing and engineering porosity in microelectronic "low-K" dielectric films, in thin polymeric permeation filters, and in catalytic films is attracting intense research interest. On the other hand, preventing interfacial defect porosity is a long-standing problem in structural materials such as adhesives, encapsulants, and composites. Traditional probes are challenged by the amorphous nature of these very thin films and by the nanoscale size of the pores/defects. PALS has been demonstrated to be an important new tool in characterizing nanoscale porosity in such sub-micron film systems.As a result of the previous NSF-ECS grant beam-PALS is playing an important role in helping the microelectronics industry develop next-generation, low-K interlayer dielectric films. The sensitivity of PALS to the size and interconnectivity of 1-100 nanometer pores has been demonstrated. A procedure for extracting pore size distributions for closed-pore systems has been developed. PALS is found to be sensitive to Cu interdiffusion into the dielectric and the consequently required diffusion barrier layer integrity can be tested as well. This proposal will expand upon this work. Metal interdiffusion and barrier integrity/thermal stability will be studied with particular attention focussed on developing a standardized PALS testing procedure as requested by Sematech, a research consortium primarily comprised of the major U.S. electronics corporations. Cross-calibration experiments with complementary techniques used to characterize porosity, such as small-angle neutron scattering (SANS) at NIST and solvent absorption ellipsometric porosimetry at IMEC, will be continued. Such studies help determine the unique strengths and weaknesses of each respective technique.A second major thrust of this proposal will be the study of polymer thin films, surfaces and interfaces. Ibis research builds upon previous work in which beam-PALS was used to study the structure and dynamics of thin 10 urn polymer films constrained on silicon wafers. Such films were found to have a highly immobile "adhesive" layer next to the silicon and an unconstrained "liquid" layer at the surface. Particular attention will be focussed on the interfacial regions in order to determine the sensitivity of the immobile layer to the onset of adhesion failure and delamination. If failure is due to the coalescence of precursor nano-voids into larger pores due, for example, to fatigue, thermal stress, or corrosion, depth-profiled beam-PALS should be a very powerful probe of this pre-failure initiation phase that is otherwise invisible. Specifically, the role of defect voids in the failure of polymer encapsulants and adhesives used in microelectronic packaging will be studied. An ancillary study of the evolution of nanostructure in a chemically amplified photo-resist as it develops under UV exposure will also be performed.The proposed research builds upon a strong existing collaboration between the University of Michigan Physics Department and the Materials Science and Engineering Department. To provide critical guidance and clear focus on relevance the PIs have developed strong working collaborations with six individual companies, NIST, and with two large industrial consortiums; Sematech in the U.S. and IMEC in Europe.