Dynamics of Point Defect/Impurity Interactions and Clustering Due to Ion Implantation and Thermal Annealing

该项目的目的是更好地了解高能低质量和中等质量离子注入对晶体硅造成的损伤，并对GaN和SiC中的类似效应进行调查研究。先前的研究确定，注入后剩余的大部分点缺陷被捕获在缺陷簇/无序区域中。团簇随后重新发射点缺陷退火过程中，产生一个稳定的缺陷复合物的光谱。结果还表明，在80 K和室温注入后，除了在投影区Rp附近产生预期的间隙位错层和在表面与Rp之间的富空位缺陷带（称为Rp/2层）外，还产生了另一个未知起源的缺陷层，其深度为Rp的2 ~ 3倍。对这种行为的物理学的理解会影响超浅pn结的性能，以及对杂质吸杂和瞬态增强扩散现象的注入后退火缺陷动力学的正确建模。除了提供关于晶体中点缺陷过饱和过程的新的基础数据外，该项目还寻求控制/抑制这些现象的选择，特别是在注入过程中。一般的方法是在从~ 80 K开始的宽温度范围内，使用非常低的注量MeV离子来研究单个碰撞级联中的缺陷积累和演化。这种注入的可忽略的级联重叠隔离了固有的级联内点缺陷过程。使用灵敏的现场电气测量，以及广泛的和互补的一套诊断技术，允许表征的缺陷类型的频谱。卢瑟福背散射谱（RBS）和斜面抛光/蚀刻将提供总损伤数据，而双探测器符合正电子湮没谱（PAS）将提供空位/杂质鉴定。深能级瞬态谱（DLTS）和电子束感生电流（EBIC）技术将被用来识别中心与“天然”的电活动，以及那些与电活动“诱导”的氢或扩散金属杂质的陷阱。这些点缺陷/杂质现象的基础是与吸杂和近表面掺杂剂扩散的释放、扩散和捕获阶段相关的基本问题。研究的具体目标是：了解低质量和中等质量离子注入Si晶体中形成的缺陷团的结构、化学和电学性质，特别是研究团的热稳定性的物理性质，即它发射移动的点缺陷的能力，这种缺陷能够在退火过程中形成稳定的复合物;理解在投影范围区域上方（RP/2）和下方（2 RP）形成的缺陷的性质，并确定它们对掺杂剂/杂质再分布和吸杂的影响;探索光子/电场程序，控制植入物缺陷簇的属性和分布，以创建缺陷工程选项。%该项目涉及材料科学领域的基础研究问题，具有高技术相关性。先进的注入和表征技术可以更好地理解和控制基本过程，这将有助于基础材料科学和技术的进步。从研究中获得的基本知识和理解有望有助于提高实现电子和光子应用的高残留晶体质量掺杂的能力。 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。

The aim of this project is to achieve greater understanding of damage in crystalline silicon caused by energetic low and medium mass ion implantation, and to conduct a survey study of similar effects in GaN and SiC. Prior research established that most of the point defects remaining after implantation are trapped in defect cluster/disorder regions. The clusters subsequently re-emit point defects during an-nealing, producing a spectrum of stable defect complexes. It was also shown that the defect cluster dis-tribution after both 80 K and room temperature implantation produces, in addition to the expected in-terstitial dislocation layer near the projective range, Rp, and a vacancy-rich defect band between the surface and Rp (called the Rp/2 layer), another defect layer of unknown origin at depths of 2 to 3 times Rp. An understanding of the physics responsible for this behavior impacts the performance achievable from ultra-shallow pn junctions, and the correct modeling of post-implantation annealing defect dy-namics which are operative in impurity gettering and transient enhanced diffusion phenomena. In addi-tion to providing new fundamental data on processes in crystals with point defect supersaturations, this project seeks options for control/suppression of these phenomena, particularly during the implantation itself. The general approach is to study defect accumulation and evolution within individual collision cascades using very low fluence MeV ions over a wide temperature range starting from ~ 80 K. The negligible cascade overlap for such implants isolates intrinsic intra-cascade point defect processes. The use of sensitive in-situ electrical measurements, together with a broad and complementary set of diag-nostic techniques allows characterization of a spectrum of defect types. Rutherford Backscattering Spectroscopy (RBS) and bevel-polish/etching will provide total damage data, while two-detector coin-cidence Positron Annihilation Spectroscopy (PAS) will provide vacancy/impurity identification. Deep level transient spectroscopy (DLTS) and electron beam induced current (EBIC) techniques will be used to identify centers with "native" electrical activity, as well as those with the electrical activity "in-duced" by trapping of hydrogen or diffusing metal impurities. Underlying these point defect/impurity phenomena are fundamental issues related to the release, diffusion, and capture stages of gettering and near-surface dopant diffusion. Specific objectives of the research are to: understand structural, chemi-cal, and electrical properties of the defect clusters formed in Si crystals due to implantation with low and medium mass ions; specifically examine the physical properties of cluster thermal stability, its ability to emit mobile point defects, which enable the formation of stable complexes during annealing; understand the nature of defects formed above(RP/2) and below(2RP) the projected range region and determine their impact on dopant/impurity redistribution and gettering; explore photon/electric field procedures which enable control of implant defect cluster properties and distribution in order to create defect engineering options.%%%The project addresses basic research issues in a topical area of materials science with high technologi-cal relevance. Advanced implantation and characterization techniques allow greater understanding and control of elementary processes which will allow advances in fundamental materials science and tech-nology. The basic knowledge and understanding gained from the research is expected to contribute to improving the ability to achieve doping with high residual crystal quality for electronic and photonic 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.***