Quantitative analysis of gettering mechanism of Si device by using imagig plate and convergentbeam electron diffraction

安全吸杂是硅器件工艺中的重要工艺之一。本征吸杂和非本征吸杂技术已用于工业化生产。本征吸杂使用通过热处理在Si晶片中形成的氧沉淀物。晶格应变或晶格缺陷被认为是杂质元素的吸杂槽。吸杂槽的定量分析对了解吸杂机理和提高吸杂效率具有重要意义。特别是，它是感兴趣的，以分析局部晶格应变吸杂汇附近。与X射线衍射或拉曼光谱相比，电子衍射能以更高的空间分辨率测量局域晶格应变，本文观察了在氧气氛中1000 ℃热处理产生氧沉淀的Si晶片的电子显微镜图像和会聚束电子衍射（CBED）图。氧沉淀物是厚度为几nm、边长为几百nm的薄板。该板与Si基体的（100）面平行，边缘与（110）面平行。从平行于沉淀物板的沿着[012]方向观察的CBED图案，测量Si基体的局部晶格应变作为与沉淀物表面的距离的函数。在压应力作用下，沉淀物板状面附近的Si晶格畸变约4%，而在拉应力作用下，沉淀物边缘附近的Si晶格畸变约3%。晶格应变随着距离界面的距离的增加而减小，并在约1 μ m处消失。

Inmurity gettering is one of the important processes in Si device process. The extrinsic or intrinsic gettering technique has been used in the commercial process. The intrinsic gettering uses oxygen precipitates formed in Si wafers by heat-treatments. Lattice strains or lattice defects are considered to be gettering sinks for impurity elements. The quantitative analysis of the gettering sinks is very important to understand the gettering mechnaism and to improve gettering efficiency. In Particular it is of interest to analyze local lattice strains near the gettering sinks. Electron diffraction enables us to measure local lattice strains in high spatial resolution compared with X-ray diffraction or Ramann spectroscopy.Electron microscope images and convergent-beam electron diffraction (CBED) patterns are observed in Si wafer which is heattreated at 1000 ﾟC in oxygen atmosphere to produce oxygen precipitates. An oxygen precipitate is thin plate of several nm in thickness and several hundred nm in edge length. The plate is paralle to (100) plane of Si matrix, and the edge is parallel to (110). From the CBED patterns ovserved along [012] direction parallel to the plate of the precipitate, local lattice strains of Si matrix are measured as a function of the distance from a surface of the precipitate. Si lattices are distorted about 4% near the plate plane of the precipitate by the compressive stress, while they are distorted about 3% near the edge of the precipitate by the tensile stress. The lattice strains decrease with increase of a distance from the interface and disappear at about 1 mum.