SiC/SiO_2界面的原子分辨率三维重构

Atomic resolution 3D reconstruction of SiC/SiO_2 interface

碳化硅(Si C)作为一种新型材料被广泛应用于高功率半导体器件中。目前的Si C基金属氧化物半导体场效应晶体管器件存在的主要问题是沟道电子迁移率低。Si C/Si O2界面处的过渡层被认为是造成沟道电子迁移率低的主要原因,但是该过渡层的原子结构尚不清楚。本文利用球差矫正扫描透射电子显微镜深入研究了Si C/Si O2的界面。以变聚焦序列技术得到了界面过渡层不同深度的原子分辨率断层扫描图像,用变聚焦序列图像重构了界面的原子分辨率三维结构。精确的界面原子结构表明Si C/Si O2界面处的过渡区是由于邻晶界面上台阶突起和微刻面构成的。它是界面原子尺度的粗糙度的反映。邻晶界面上的台阶突起和微刻面增加了电子在界面传输过程中的散射几率,造成了沟道电子迁移率过低。

Silicon carbide （ SiC） is widely used in high power electronics as a substitute of silicon. The key problem of SiC based metal？oxide？semiconductor field effect transistors （ MOSFET） is the relatively low channel electron mobility, and the transition layer of SiC/SiO2 interface is considered to be the main cause for the reduced electron mobility. However, the atomic structure of the transition layer is still unclear. In this paper, the transition layer was investigated with a 5th order spherical aberration corrected scanning transmission electron microscope. Depth sectioning images of SiC/SiO2 interface were obtained with the through-focal series technique, and an atomic resolution 3D structure of the interface was reconstructed with the through-focal series images. The clear 3D interface structure suggests that tshe interface has an atomic scale roughness, and the transition layer is a contrast of the roughness. The kinks, steps and microfacets increase the scattering probability of channel electrons, resulting in reducing the channel mobility of the MOSFET devices.