高质量6英寸4H-SiC同质外延层快速生长

Fast Growth of High Quality 6 Inch 4H-SiC Homoepitaxial Layer

采用化学气相沉积法在6英寸(1英寸=2.54 cm)4°偏角4H-SiC衬底上进行快速同质外延生长,通过研究Si/H_(2)比(所用气源摩尔比)与生长速率的相互关系,使4H-SiC同质外延层生长速率达到101μm/h。同时,系统研究了C/Si比对4H-SiC同质外延层生长速率、表面缺陷密度和基面位错密度的影响。采用光学显微镜和表面缺陷测试仪对同质外延层缺陷形貌以及缺陷数量进行表征。结果表明,当C/Si比不小于0.75时,4H-SiC同质外延层生长速率趋于稳定,约为101μm/h,这是沉积表面硅源受限导致的。此外,随着C/Si比增加,4H-SiC同质外延层表面缺陷密度明显增多,而衬底基面位错(BPD)向刃位错(TED)转化率几乎接近100%。因此,当生长速率约为101μm/h、C/Si比为0.77时能够获得高质量、高一致性的4H-SiC同质外延片,其外延层表面缺陷和基面位错密度分别为0.39 cm^(-2)和0.14 cm^(-2),外延层厚度和掺杂浓度一致性分别为0.86%和1.80%。

Fast homoepitaxial growth was performed on 6 inch(1 inch=2.54 cm) 4H-SiC substrate with 4° drift angle using chemical vapor deposition method. Through the investigation of the correlation of the Si/H_(2) ratio(the mole ratio of the used gas sources) and growth rate, the growth rate of the homoepitaxial layer reaches to 101 μm/h. Meanwhile, the effects of the C/Si ratio on the growth rate, surface defect density and basal plane dislocation density of the 4H-SiC homo-epitaxial layer were systemically studied. The optical microscope and surface defect analyzer were used to characterize the morphology and amount of the defects for the 4H-SiC homoe pitaxial layer. The result indicates that the growth rate tends to be stable and is about 101 μm/h when the C/Si ratio is no less than 0.75, which is due to the limitation of the silicon source on the deposition surface. In addition, the surface defect density of the 4H-SiC homoeptiaxial layer obviously increases with the increase of the C/Si ratio, but the conversion rate of the basal plane dislocation(BPD) in the substrate to the threading edge dislocation(TED) is closed to 100%. Therefore, when the growth rate is 101 μm/h and the C/Si ratio is 0.77, the 4H-SiC homoe pitaxial wafer with high quality and high uniformity can be obtained. The surface defect density and basal plane dislocation density of the 4H-SiC homoe pitaxial layer are 0.39 cm^(-2) and 0.14 cm^(-2), and the uniformities of the thickness and doping concentration for the epitaxial layer are 0.86% and 1.80%, respectively.