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（Stony Brook）和Cape simulation公司的研究人员与晶体生长公司（Cree Research, Inc., Epitronics, Inc., Northrop Grumman Corp., Airtron-Litton Corp.和II-VI， Inc.）的合作努力，以研究SiC晶体缺陷的成核机制。该项目的目标是促进对碳化硅圆管中扩展缺陷成核和演变的过程的理解。特别是基面位错和螺旋位错、层错、微管和低角度畴边界将被研究。该方法包括三个重点：(i)模拟碳化硅物理蒸汽输运生长，重点是不同生长阶段的热弹性应力。在PVT生长中常见的小的第二相包裹体周围的局部应力场也将被模拟。（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最小化缺陷成核。关键工艺参数将调整，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，随后进行非原位结构表征。（iii） SiC晶体的结构表征将通过同步加速器白束x射线形貌（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。基面位错密度和基面总弯曲将确定并与宏观应力分布相关联。通过x射线形貌和透射电镜观察了螺位错在生长早期的形核及其与堆积无序和夹杂的关系。利用HRXRD测量蚀刻低角晶界上的错取向成分，并解释其来源。该项目涉及具有高潜在技术相关性的材料科学主题领域的基础研究问题。该研究将在基础水平上为电子/光子学中重要的块状晶体生长提供基础材料科学知识。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。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。他们将使用和改进过程模拟工具，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).***