4HN-SiC包裹物在薄层同质外延中的转化

Conversion of 4HN-SiC Inclusions in the Thin Layer Homogeneous Epitaxy

对4HN型碳化硅(4HN-SiC)包裹物进行了系统的研究,首次提出了包裹物分布的碳氮竞位模型,并对各种包裹物的起源及抑制改善提出了有效的解决方法。同时研究了4HN型SiC包裹物在薄层同质外延过程中的转化,发现外延后包裹物主要转化为三角形、凸起和凹坑三种表面缺陷。对比外延前后缺陷形貌发现,包裹物外延后呈现的表面缺陷类型主要取决于包裹物的大小和聚集密度。在工艺优化过程中,发现低碳硅比环境下来源于包裹物的表面"杀手级"缺陷数量明显降低。这是由于随着碳硅比的降低,外延过程中台阶流生长占主导,减少了岛状成核点。通过对生长单晶抛光片和外延片工艺的优化,制备出外延后无包裹物导致的表面"杀手级"缺陷的高质量4HN-SiC外延片,其合格率达到99.3%。

The inclusions of 4 HN type silicon carbide(4 HN-SiC)were systematically studied,a model of carbon nitrogen competition for inclusion distribution was firstly provided,and an effective solution method to the origin and inhibition of various inclusions was proposed.Meanwhile,the conversion of 4 HN-SiC inclusions in the thin layer homogeneous epitaxial process was studied.It is found that the inclusions after epitaxy are mainly transformed into the three kinds of surface defects:triangle,bulge and pit defects.Comparison results of the defect morphologies before and after epitaxy show that the surface defect type of inclusions after epitaxy depends on the size and packing density of inclusions.It is observed that the surface killer defects resulting from the inclusions can be obviously suppressed under the lower carbon silicon ratio condition in the optimization process.The reason is that the step flow growth takes the dominant role and island nucleation site is reduced in the epitaxial process under the condition of lower carbon silicon ratio.By the growth processing optimization of single crystal polished wafers and epitaxial wafers,a high quality 4 HN-SiC homoepitaxial wafer without the killer defects induced by the inclusions was obtained.And its yield reaches 99.3%.