Development of in-sutu observation system for internal stress fields due to lattice defects using the infrared photoelastic method

为了开发高质量的大直径硅片，必须控制硅片中的位错等晶格缺陷。多晶硅近年来也受到了广泛的关注，但要发展多晶硅的实用化，提高其力学性能是必然的。为了研究硅晶体的这种力学性能和晶格缺陷，直接观察晶体中由这些晶体缺陷引起的内部应力场是非常有用的。本课题研究的重点是利用红外光弹性方法研制晶格缺陷内部应力场的实时观测系统。利用该系统，对硅晶体致密拉伸试样中裂纹尖端周围的应力场进行了原位观测。本文还对光弹性图像进行了模拟，结果与实验结果吻合较好。此外，在本研究项目中，我们观察了硅薄晶体中裂纹尖端周围产生的位错的详细构型，这不仅对了解硅片的韧性至关重要，而且对研究本系统获得的光弹性图像的物理意义也至关重要。

In order to develop high quality silicon wafer with large diameter, it is essential to control lattice defects such as dislocations in those wafers. Polycrystalline silicon has also received much attention recently, but it is inevitable to improve its mechanical property for developing their practical use. In order to investigate such mechanical property and lattice defects of silicon crystals, it is very useful to make direct observation of internal stress fields caused by those crystal defects in crystals.The essential point in the present research project is to develop the in-sutu observation system for internal stress fields due to lattice defects by using the infrared photoelastic method. By using this system, we made in-situ obaervation of crack tip stress fields developed around a crack tip in compact tension specimen of silicon crystals. The simulation of photoelastic images has been also made, and we have obtained a good agreement with those experimentally observed. In addition, in this research project, we observed the detailed configurations of dislocations generated around a crack tip in silicon thin crystals, which is essential not only to understand the toughness of silicon wafer, but also to study the physical meaning of the photoelastic images obtained by the present system.