偏4°4H-SiC同质外延层上新形貌三角形缺陷研究

New Type of Triangular Defects in 4H-SiC 4°Off-Axis Homoepitaxial Layers

利用水平热壁CVD方法,基于SiH4-C3H8-H2生长系统在n型4H-SiC偏4°衬底上进行同质外延生长。通过Nomarski光学显微镜、激光共聚焦显微镜和拉曼散射光谱(Raman),对外延层中的新形貌三角形缺陷——顶端有倒金字塔结构的三角形缺陷(IPRTD)的表面形貌、结构进行了表征,并根据表征结果提出了该新形貌三角形缺陷的产生机理。研究结果表明,IPRTD由3C-SiC晶型构成;在外延生长中,位于IPRTD生长方向上游的位错缺陷所引起的表面吸附原子的2D成核生长是导致3C-SiC晶型出现的主要原因。同时,外延生长过程中,生长速率和氢气刻蚀作用在[112-0]和[11-00]/[1-100]方向上的差异是导致IPRTD顶端具有倒金字塔结构的主要原因。

In this work,4H-SiC epilayers were performed on 4°off-axis Si-face substrates by horizontal hot wall chemical vapor deposition(CVD)with a standard chemistry of silane-propane-hydrogen.A new type of triangular defect with inverted pyramid located at its apex(IPRTD)was observed.The morphology,microstructure and formation mechanism of the triangular defect were investigated by Nomarski optical microscope,laser scanning confocal microscope and micro-Raman spectroscopy.Characterization results indicates that the triangular defect observed has a 3C-SiC nature.Based on these observations and analysis,a model of the formation mechanism of the triangular defect was proposed.In this model,the origination of IPRTD is attributed to 2D nucleation caused by dislocation located on the upstream of the growth direction.The difference in the growth rates between the step-flow growth direction of[112-0]and lateral growth along with the directions of[11-00]/[1-100]as well as the etching of the epitaxial layer by hydrogen are the main reasons for the formation of the inverted pyramid structure at the top of the defect.