直拉法单晶硅中位错影响因素研究进展

Research Progress on Influencing Factors of Dislocation in Czochralski Silicon

在介绍了直拉法单晶硅中位错形成及运动机理的基础上,归纳了其生长过程中籽晶热冲击、固液界面、晶体直径和杂质等因素对位错的影响,分析了硼、锗、氮、磷、砷掺杂元素和氧杂质对单晶硅位错行为的影响.籽晶热冲击会引起位错,而通过缩颈、回熔、籽晶预热以及采用掺杂的籽晶等方式可以使其得到抑制.凸向熔体的固液界面引起较大的边缘切应力产生边缘位错,当形状为平面时,可抑制位错形成;在重掺n型单晶硅中,固液界面的演变和{111}边缘面的形成可能促进过冷区域产生并中断顶锥生长,进而引发位错,并且边缘面的长度与熔融等温线的曲率有关;引晶时籽晶的不完全引晶,会产生位错且无法排出晶体,进而延伸至硅棒中;单晶硅直径增大和长晶过程中的直径波动都会增加位错的形成风险.掺杂是抑制位错形成与运动的有效方法,硼、锗、氮、磷、砷以及氧杂质对位错都起着不同程度的抑制作用,主要原因在于杂质原子对位错的钉扎效应.最后,针对缩颈工艺、热场设计、掺杂工艺和理论建模等方面,对未来的研究工作做出了展望.

Based on the introduction of the dislocation formation and movement mechanism in Czochralski silicon,the effects of seed crystal thermal shock,solid-liquid interface,crystal diameter,and impurities on the dislocations during the crystal growth process were summarized.The effects of boron,germanium,nitrogen,phosphorus,arsenic doping elements and oxygen impurities on the dislocation behavior of the Czochralski silicon were analyzed.The thermal shock of the seed crystal can lead to the dislocations,which can be suppressed by some methods such as necking,melting back,seed crystal preheating,and the use of doped seed crystal.The solid-liquid interface convex to the melt causes a large edge shear stress to produce the edge dislocations.The formation of dislocations can be suppressed when the shape is flat.In heavily w-type doped single crystal silicon,the evolution of solid-liquid interface and the formation of{111}edge surface may promote the generation of supercooling region and interrupt the growth of top cone,thereby causing the dislocations,and the length of the edge surface is related to the curvature of the melting isotherm.Incomplete seeding of the seed crystal will produce the dislocations that cannot be discharged from the crystal,and then extend to the silicon rod.The increase in the diameter of single crystal silicon and the fluctuation of the diameter during the crystal growth process will increase the risk of dislocation formation.Doping is an effective method to inhibit the formation and movement of dislocations.Boron,germanium,nitrogen,phosphorus,arsenic and oxygen impurities all have different degrees of inhibition on the dislocations mainly due to the pinning effect of impurity atoms on the dislocations.Finally,some future research aspects on necking process,thermal field design,doping process and theoretical modeling were prospected.