Development of laser terahertz emission microscope and its application to LSI defect analysis

本项目旨在研制一种激光太赫兹（THz）发射显微镜（LTEM）并探索其应用。其原理是利用飞秒激光照射下由多种电子材料激发的太赫兹辐射。本文的研究课题是：1)设计和制造LTEM原型；2)评估其性能和改进；3)观察各种电子材料和器件的应用。我们研制了一种具有反射模式和透射模式的自由空间型和扫描光纤探头型激光瞬变电磁法。采用模态制线和空间试样对其性能进行了评价。自由空间型和探头型的最小分辨率分别大于2 μm和1.5 μm。首先，用tem观察了多铁BiFeO_3 （BFO）薄膜的铁电畴。我们首次发现了BFO的太赫兹辐射效应，并成功地实现了其强电畴的可视化。然后，我们应用LTEM在运算放大器工作时成像，并成功地可视化了器件中与放大过程相关的唯一信号线。最后，探讨了该方法在LSI缺陷分析中的应用。我们成功地区分了测试元件组中损坏的MOSFET和未损坏的MOSFET。结果证明，LTEM是一种很有前途的新型显微镜，可用于大规模集成电路和各种电子材料的器件评价。可以预期，ltm可以改进到可用于动态显微镜。

This project aims to develop a laser terahertz (THz) emission microscope (LTEM) and explore its applications. The principle uses the THz radiation excited from many electronic materials with an illumination of femtosecond laser. The research subjects examined here are 1) designing and manufacturing the prototype of LTEM, 2) the evaluation of its performance and improvement, and 3) applications to observe various electronic materials and devices.We developed a free space type and scanning fiber probe type LTEM with either reflection mode or transmission one. The performance has been evaluated by using mode made line and space specimen. The minimum resolution for the free space type and probe one is better than 2 μm and 1.5 μm, respectively.First, the LTEM has been applied to see ferroelectric domain in multiferroic BiFeO_3 (BFO) thin films. We discovered the THz emission effect from BFO for the first time, and successfully visualized the feroelectoric domain. Then we applied LTEM to image an operational amplifier while operating, and successfully visualized the only signal lines related to amplifying process in the device. Finally, we examined its application to LSI defect analysis. We success fully distinguished damaged MOSFET in the Test Element Group from undamaged. The results prove that LTEM is promising new type of microscope for device evaluation such as LSI as well as various electronic materials. One can expect that LTEM can be improved to be available for dynamic microscope.