Mechanisms of Extended Defect Nucleation During PVT Growth of Silicon Carbide

这个GOALI项目代表了卡内基梅隆大学、纽约州立大学（斯托尼布鲁克）和Cape Simulations Inc.的研究人员之间的合作努力，与晶体生长公司Cree Research，Inc.，Epitronics，Inc.，诺斯罗普·格鲁曼公司，Airtron-Litton Corp.，和II-VI公司研究SiC中晶体缺陷的形核机制。该项目的目标是促进对SiC晶锭中扩展缺陷的成核和演变过程的理解。特别是基面和螺旋位错，堆垛层错，微管，和低角度域边界将进行研究。该方法包括三个推力：（i）碳化硅物理气相传输生长的建模，重点是在不同阶段的生长热弹性应力。在PVT生长中常见的小的第二相夹杂物周围的局部应力场也将被建模。(ii)SiC PVT生长实验将在一个小规模的PVT系统中进行，在精心优化的条件下选择，以尽量减少缺陷成核。关键的工艺参数将被调整，以测试模型的缺陷成核和增殖。生长将在不同阶段（特别是早期播种阶段）中断，然后进行异位结构表征。(iii)SiC晶体的结构表征将通过同步加速器白色束X射线形貌术（SWBXT）、原子力显微镜（AFM）、透射电子显微镜、蚀刻和高分辨率X射线衍射（HRXRD）进行。基面位错的密度和基面的总弯曲将被确定并与宏观应力分布相关联。在生长的早期阶段，螺旋位错的形核及其与堆垛无序和夹杂物的关系将通过X射线形貌术和TEM观察。通过HRXRD测量蚀刻揭示的小角度晶界上的取向差分量，并解释其来源。该项目涉及材料科学专题领域的基础研究问题，具有很高的潜在技术相关性。这项研究将有助于在基础水平的基础材料科学知识，以体晶体生长重要的电子/光子学。从研究中获得的基本知识和理解有望有助于提高先进设备的成本，性能和稳定性。 该计划的一个重要特点是通过在一个基本和技术上重要的领域对学生进行培训来整合研究和教育。参与该项目的研究生将获得与团队成员合作的多方面经验。他们将使用和改进工艺模拟工具，生长和表征SiC晶体，参与技术转让，并将在学术和工业环境中工作。该项目由DMR/电子材料计划和MPS OMA（多学科活动办公室）共同支持。

This GOALI project represents a collaborative effort between researchers at Carnegie Mellon University, SUNY (Stony Brook), and Cape Simulations Inc., together with crystal growth companies: Cree Research, Inc., Epitronics, Inc., Northrop Grumman Corp., Airtron-Litton Corp., and II-VI, Inc. to investigate nucleation mechanisms of crystalline defects in SiC. The objectives of the project are to advance the understanding of processes responsible for nucleation and evolution of extended defects in SiC boules. In particular basal plane and screw dislocations, stacking faults, micropipes, and low angle domain boundaries will be investigated. The approach consists of three thrusts:(i) Modeling of silicon carbide Physical Vapor Transport growth with emphasis on thermoelastic stresses at different stages of growth. Local stress fields around small second phase inclusions common in PVT growth will also be modeled. (ii) SiC PVT growth experiments will be performed in a small scale PVT system in carefully optimized conditions selected to minimize defect nucleation. Critical process parameters will be adjusted to test models of defect nucleation and multiplication. Growth will be interrupted at different stages (in particular early seeding stages), followed by ex situ structural characterization. (iii) Structural characterization of SiC crystals will be performed by synchrotron white beam x-ray topography (SWBXT), Atomic Force Microscopy (AFM), transmission electron microscopy, etching and high resolution x-ray diffraction (HRXRD). Density of basal plane dislocations and total bending of basal plane will be determined and correlated with macroscopic stress distributions. Nucleation of screw dislocations at early stages of growth and their association with stacking disorder and inclusions will be observed by x-ray topography and TEM. Misorientation components across low angle grain boundaries revealed by etching will be measured by HRXRD and their origin interpreted.%%%The project addresses basic research issues in a topical area of materials science having high potential technological relevance. The research will contribute basic materials science knowledge at a fundamental level to bulk crystal growth important to electronics/photonics. The basic knowledge and understanding gained from the research is expected to contribute to improving the cost, perform-ance and stability of advanced devices. 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. Graduate students participating in this project will gain multifaceted experience collaborating with team members. They will work with and improve process simulation tools, grow and characterize SiC crystals, take part in technology transfer, and will be exposed to work in both academic and industrial environments. The project is co-supported by the DMR/Electronic Materials program and the MPS OMA(Office of Multidisciplinary Activities).***