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中国物理学会期刊

X射线形貌方法在4H-SiC晶圆缺陷表征中的应用

Application of X-ray Topography in Defect Characterization of 4H-SiC Wafer

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  • 晶体缺陷作为制约半导体器件电学性能、成品率及可靠性的关键物理因素,其对材料宏观物性的制约已成为根本性科学问题。X射线形貌术是研究近完美晶体中长程应变场的关键技术,其理论依据是X射线在周期性畸变晶格中的动力学衍射理论。本研究以宽禁带半导体的典型代表-碳化硅(SiC)单晶为模型系统,运用X射线形貌学方法对其中存在的螺旋位错、刃型位错及基平面位错进行系统的物理表征。研究重点讨论了基于消衬准则对位错柏氏矢量进行定量判定的方法学,并分析了不同衍射几何下的衬度特征。本文揭示了X射线形貌技术作为定量探究晶体缺陷物理的科学方法的内在价值。

    Crystal defects significantly constrain the electrical performance, yield, and reliability of semiconductor devices, making their physical characterization a fundamental scientific imperative. X-ray topography (XRT) serves as a pivotal non-destructive metrology tool for investigating long-range strain fields in nearly perfect crystals, grounded in the dynamical diffraction theory of X-rays. Using 4H-SiC—a representative wide-bandgap semiconductor—as a model system, this study systematically investigates the physical characteristics of threading screw dislocations (TSDs), threading edge dislocations (TEDs), and basal plane dislocations (BPDs). We comprehensively employ multiple synchrotron X-ray diffraction geometries, including reflection, grazing incidence, plane-wave rocking curve imaging (RCI), and transmission topography.
    A rigorous methodology for the quantitative determination of dislocation Burgers vectors based on extinction criteria is established. Notably, utilizing the beam expansion effect in grazing incidence topography, a macroscopic dislocation density map of a full 6-inch 4H-SiC wafer is successfully extracted, enabling highly efficient defect statistical analysis. Furthermore, by utilizing plane-wave RCI, we quantitatively map the local lattice rotations and stress fields induced by single TSDs through full width at half maximum (FWHM) and peak shift variations, intuitively verifying their spiral characteristics. Finally, through cross-sectional transmission topography and three-dimensional volumetric reconstruction, an unprecedented three-dimensional defect network map is achieved, directly visualizing the spatial distribution and interactive evolution of TSDs, TEDs, and BPDs along the crystal growth direction. The findings and the established comprehensive XRT protocol provide profound physical insights into defect dynamics and stress relaxation mechanisms, offering critical engineering value for optimizing SiC crystal growth processes and enhancing the yield of next-generation power electronics.

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