GOALI/FRG: Nanoscale Morphological Control of Strained Semiconductor Surfaces

这个FRG/GOALI项目是弗吉尼亚大学和位于纽约约克镇海茨的IBM研究人员之间的合作成果。与美国伊利诺伊大学厄巴纳-香槟分校建立了其他合作；弗吉尼亚州Farmville的Longwood学院；的联合;和桑迪亚国家实验室。该方法旨在研究晶格错配异质外延薄膜的应变弛豫途径，目的是获得足够的基本理解表面粗糙化和界面位错在外延层松弛时所起的作用，从而允许异质外延薄膜的形态“编程”。研究人员试图通过在初始生长表面上引入扰动（表面台阶、界面位错和/或光刻定义的图案）来获得定义脱毛层最终形态的知识和能力。这种编程表面在后续纳米级结构（如图案量子点阵列和功能性生物分子）模板中的应用也将被探索。这种可编程性既不依赖于自发的自组装，也不依赖于光刻。相反，它寻求协同效应，可能为实际纳米结构制造提供突破。最初，实验将集中在GeSi/Si系统上。将研究一系列的生长技术（分子束外延、气源分子束外延和超高真空化学气相沉积），从而推断出一般的机制，而不是特定的生长化学或结构。均匀（即非扰动）表面的演化研究将集中在应变解除的微观机制和整体应变状态的宏观测量上。形态演化和错配位错注入的竞争和相互依赖将被详细研究。实验技术将包括非原位和原位透射电子显微镜（TEM），原位低能电子显微镜（LEEM）， x射线衍射的二维倒易晶格映射，原位晶圆曲率和光谱光散射测量，有限元分析（FEA）计算，以及使用TEM成像和衍射的局部应变映射。通过脱毛层粗化进行应变松弛的定量测量将纳入现有的模拟器，该模拟器是在先前的NSF资助下开发的，该模拟器模拟错配位错注入晶格不匹配异质结构。结合模拟器将提供一个完整的描述应变松弛，形态演变和位错的产生在一系列的异质外延系统。对微扰机制和可编程表面的后续研究将应用许多相同的工具，重点是局部敏感探针，如基于TEM， LEEM和fea的技术。该项目涉及材料科学中具有高技术相关性的主题领域的基础研究问题。从研究中获得的基本知识和理解有望有助于提高半导体材料在当前和未来器件和电路应用中的性能。该计划的一个重要特点是通过培养学生在一个基础和技术上重要的领域的研究和教育的整合。这个GOALI项目的多学科（材料科学、电气工程、物理）和工业联系性质为学生提供了独特的教育机会，让他们从学术和工业的角度体验以团队合作为导向的研究环境

This FRG/GOALI project is a collaborative effort between researchers at the University of Virginia and IBM, Yorktown Heights, NY. Additional collaborations are established with U. IL, Urbana-Champaign; Longwood College, Farmville, VA; UCB; and Sandia National Laboratories. The approach is to investigate pathways for strain-relaxation of lattice mismatched heteroepitaxial films with the goal of gaining sufficient fundamental understanding of the roles that surface roughening and interfacial dislocations play as the epilayer relaxes to allow morphological 'programming' of heteroepitaxial films. The investigators seek to acquire the knowledge and ability to define the final morphology of an epilayer by introducing perturbations--surface steps, interfacial dislocations and/or lithographically defined patterns--onto the initial growth surface. Applications of such programmed surfaces for templating of subsequent nanoscale structures such as patterned quantum dot arrays and functional biological molecules will also be explored. This programmability places total reliance on neither spontaneous self-assembly nor lithography. Instead, it seeks out synergistic effects that may provide breakthroughs in practical nanostructure fabrication. Initially, experiments will concentrate upon the GeSi/Si system. A range of growth techniques (molecular beam epitaxy, gas source molecular beam epitaxy, and ultra-high vacuum chemical vapor deposition) will be studied, to enable general mechanisms to be inferred, rather than those particular to a particular growth chemistry or configuration. Studies on the evolution of uniform (i.e. non-perturbed) surfaces will focus upon both microscopic mechanisms of strain relief and macroscopic measurements of the overall strain state. The competition and inter-dependence of morphological evolution and misfit dislocation injection will be examined in detail. Experimental techniques will include ex-situ and in-situ transmission electron microscope (TEM), in-situ low energy electron microscope (LEEM), two dimensional reciprocal lattice mapping with X-Ray diffraction, in-situ wafer curvature and spectroscopic light scattering measurements, finite element analysis (FEA) calculations, and local strain mapping using TEM imaging and diffraction. Quantitative measurements of strain relaxation by epilayer roughening will be incorporated into an existing simulator, developed under a previous NSF grant, that models misfit dislocation injection into lattice-mismatched heterostructures. The combined simulator will provide a complete description of strain relaxation, morphological evolution and dislocation generation in a range of heteroepitaxial systems. Subsequent studies of perturbation mechanisms and programmable surfaces will apply many of the same tools, with emphasis on locally sensitive probes such as TEM-, LEEM- and FEA-based techniques.%%%The project addresses basic research issues in a topical area of materials science with high technological relevance. The basic knowledge and understanding gained from the research is expected to contribute to improving semiconductor materials performance in current and future device and circuit applications. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. The multidisciplinary (materials science, electrical engineering, physics) and industrially-connected nature of this GOALI program offers unique educational opportunities for students to experience a teamwork-oriented research environment from both academic and industrial perspectives.***