4H-SiC晶体中的螺位错演变规律研究

doi:10.15541/jim20250509

摘要/Abstract

摘要： 螺位错(Threading Screw Dislocation, TSD)是碳化硅(Silicon Carbide, SiC)单晶中影响外延质量和器件性能的重要缺陷。随着 SiC 晶圆尺寸不断增大,系统研究 TSD 的演变规律具有重要意义。本工作针对4H-SiC晶体中的螺位错演变规律开展研究,阐明晶体生长凸度对 TSD 产生的影响。采用物理气相传输法(Physical Vapor Transport, PVT)在不同热场条件下制备凸度为 0.36~2.58 mm 的 4H-SiC 单晶。利用 X 射线形貌术(X-Ray Topography, XRT)对纵切样品进行表征,分析热场梯度及 C/Si 比对螺位错演变的作用。螺位错在晶体生长过程中表现出继承、新生、合并、消失、弯折等多种演变行为。初期生长阶段新增 TSD 密度随晶体凸度增大而显著升高,当凸度为 2.58 mm 时,新增 TSD 密度约为 126 cm^-2。热场模拟表明,较大的凸度对应更陡峭的热梯度和更低的 C/Si 比,易诱发硅液滴形成并促进 TSD 形核;末期新增 TSD 密度受凸度影响较小,维持在 0~3 cm^-2。晶体初期生长阶段是 TSD 形成的主要时期,热场引起的 C/Si 比失衡起主导作用。通过优化热场结构并降低生长前沿凸度,可有效抑制螺位错形成,提高大尺寸 4H-SiC 单晶质量。

关键词: 4H-SiC单晶, 螺位错, C/Si比, 热场梯度

Abstract: Threading screw dislocation (TSD) is critical defects in silicon carbide (SiC) single crystals and have a strong impact on epitaxial quality and device performance. With the increasing diameter of SiC substrates, understanding the evolution behavior of TSD during bulk growth is of growing importance. This study aims to investigate the evolution characteristics of TSD in 6-inch 4H-SiC single crystals and to clarify the influence of crystal growth front convexity on TSD generation. Four 6-inch 4H-SiC single crystals with different growth convexities ranging from 0.36 to 2.58 mm were grown by the physical vapor transport (PVT) method through thermal field regulation. Longitudinal cross-sectional samples were characterized using X-ray topography (XRT) to trace the evolution behavior of individual TSD. Thermal field simulations were performed to analyze the relationship between temperature gradient and local C/Si ratio. XRT results reveal multiple TSD evolution behaviors, including inheritance from the seed, newly generated dislocations, merging and annihilation, and bending. The density of newly generated TSD during the initial growth stage increases monotonically with crystal convexity. When the convexity increases from 0.36 to 2.58 mm, the initial newly generated TSD density rises and reaches approximately 126 cm^-2. Thermal field simulations indicate that larger convexity leads to steeper temperature gradients and a reduced C/Si ratio, promoting silicon droplet formation and TSD nucleation. In contrast, the influence of convexity on TSD generation during the final growth stage is weak, with densities remaining at 0-3 cm^-2. The results indicate that the initial growth stage is the dominant period for TSD formation, mainly governed by thermal field-induced C/Si imbalance. Optimizing the thermal field to maintain a low growth front convexity is essential for suppressing TSD formation in large-diameter 4H-SiC single crystals.

Key words: 4H-SiC single crystal, threading screw dislocation, C/Si ratio, temperature gradient

中图分类号:

TN304

赵宁, 魏福源, 汪坪, 史婷婷, 王波, 杨建, 刘春俊. 4H-SiC晶体中的螺位错演变规律研究[J]. 无机材料学报, DOI: 10.15541/jim20250509.

ZHAO Ning, WEI Fuyuan, WANG Ping, SHI Tingting, WANG Bo, YANG Jian, LIU Chunjun. Investigation of Threading Screw Dislocation Evolution in 4H-SiC Single Crystals[J]. Journal of Inorganic Materials, DOI: 10.15541/jim20250509.

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