Studies on optical nondestructive detection methods of small crystal defects in the next generation of silicon wafers

本研究旨在开发高灵敏度的光学无损检测方法来检测下一代硅衬底中的微小晶体缺陷，这是电子工业亟待解决的重要问题之一，并取得了以下研究成果：(1)为了观察作为下一代高速大规模集成电路衬底的SOI中的残余应变和晶体缺陷，研制了一种反射式红外偏光镜，用于检测探测光在穿过硅层时以及从硅层与绝缘层之间的界面反射时，由应变和缺陷引起的少量双折射。利用自行研制的激光退火仪，我们发现SOI材料SOS中晶格失配引起的残余应变和缺陷经激光退火热处理后得到了降低。通过这种方式，我们演示了反射式偏振镜开发…的有效性通过对为定性表征化合物半导体中残余应变而研制的扫描红外偏振仪的改进，研制了一种用于检测硅片红外双折射的高灵敏度扫描系统。利用该系统，我们观察到了由滑移线、OSF等引起的缺陷诱导双折射，(B)热处理过程中在保持区附近由工艺引起的双折射，(C)由硅片本身的重量引起的少量双折射。通过对高灵敏度双折射检测系统的改进，实现了对无位错硅锭中红外双折射的测量。我们发现，尽管经典的光学理论认为硅是光学各向同性的，但由于光波和局域电场的相互作用，硅中存在着少量的光学各向异性。当光波沿晶体图形方向传播时，观察到了这种光学各向异性。此外，当我们沿光学各向异性不活跃的&lt；100&gt；方向引入光波时，我们发现了极少量的双折射，可能与点缺陷的空间分布有关。这表明了我们可以表征点缺陷的分布的可能性，这到目前为止被认为是非常困难的。较少

This research has been done to develop optical nondestructive methods with high-sensitivity for detecting small crystal defects in the next generation of silicon substrates, which is one of the most important issues to be solved for electronics industries, and the following research results have been obtained ;(1) In order to observe residual strains and crystal defects in SOI which is a promising substrate for the next generation of high-speed LSI, a reflection type of infrared polariscope has been developed to detect a small amount of birefringence induced by strains and defects when the probing light is propagating through the silicon layer and also reflecting back from the interface between silicon layer and insulator. By using this instrument developed here, we found that the residual strains and defects caused by lattice mismatching in SOS, which was one of SOI, were reduced by laser annealing. In this way, we demonstrated the usefulness of the reflection type of polariscope deve … More loped here.(2) A high-sensitivity scanning system for detecting infrared birefringence in silicon wafers has been developed by improving the scanning infrared polariscope which was developed for the qualitaive characterization of residual strains in compound semiconductors. By using this system, we observed defect-induced birefringence due to slip lines, OSF, and etc., (b) process-induced birefringence caused near the holding region during thermal treatment, (c) a small amount of birefringence induced by the weight of silicon wafer itself. In this way, we demonstrated the usefulness of the high-sensitivity scanning system for detecting infrared birefringence in silicon wafers.(3) We have tried to measure birefringence in dislocation-free silicon ingot by improving the high-sensitivity birefringence detecting system. We found that there is a small amount of optical anisotropy induced by an interaction between light wave and local electric field in silicon although it was considered to be optically isotropic by a classical optic theory. This optical anisotropy was observed when the light wave was propagating along the crystallo graphic <110> direction. Furthermore, we found a extremely small amount of birefringence relating probably to spatial distribution of point defects when we introduced the light wave along the <100> direction that the optical anisotropy was not active. This is indicative of a possibility that we may characterize the distribution of point defects, which is recognized up to now to be very difficult. Less