Simultaneous detection of positive and negative scanning ion images using a focused ion beam

研制了一种利用液态金属离子源聚焦离子束扫描同时获得正负离子像的仪器。它由一次离子辐照柱、样品室、二次离子提取检测系统和数据处理系统组成。该仪器的结构特点是：扫描离子束轴垂直于样品，样品保持在水平面上，正负二次离子被相对的引出器引出到不同的方向，引出器的位置与扫描离子束轴对称。通过这种布置，由施加到提取器的电压形成的电场几乎不影响初级离子束的偏转。二次离子的检测方法如下：1）LMIS束在样品表面扫描; 2）溅射的正、负二次离子被电场分别同时提取; 3）二次离子通过轰击由铝制成的转换器而被转换成电子; 4）电子被加速朝向反射器以产生光子; 5）光电倍增管探测并放大光子信号; 6）计算机处理两路与扫描信号同步的输出信号。因此，在监视器上显示同一点的正离子图像和负离子图像。作者确认仪器各部分工作正常，能正确观察到网孔样品的正、负离子图像，并为进一步发展西姆斯分析技术，建立了测量方法。在这项研究中，二次离子图像分析的Ga-FIB的斜分层样品进行了研究。这种技术是特别有用的粗糙表面样品作为替代西姆斯深度剖析。

An instrument to simultaneously obtain the positive and negative ion images by scanning a focused ion beam (FIB) of a liquid-metal-ion source (LMIS) has been developed. It consists of primary ion irradiation column, sample chamber, extracting and detecting system for secondary ions, and data processing system. The structural features of the instrument are as follows: scanning ion beam axis is perpendicular to the sample which is held in a horizontal plane; the positive and negative secondary ions are extracted to the separate directions by extractors which face each other in a symmetrical position to the scanning beam axis. By this arrangement the electric field formed by the voltages applied to the extractors hardly affects the deflection of the primary ion beam. The secondary ions are detected as follows: 1) an LMIS beam scans on the sample surface; 2) the sputtered positive and negative secondary ions are separately and simultaneously extracted by the electric fields; 3) the secondary ions are converted to electrons by bombarding the converters made of aluminum; 4) the electrons are accelerated toward scintillators to generate photons; 5) the photon signals are detected and amplified by photomultipliers; 6) two channels of output signals synchronized with the scanning signal are processed by computer. Thus the positive and negative ion images of the same point are displayed on a monitor. The author confirmed that each part of the instrument normally works, and that the positive and negative ion images of a mesh sample are properly observed.Moreover, to further advance the SIMS analyzing technique the measuring method was also developed. In this study, the secondary ion image analysis by Ga-FIB on a beveled layered sample was investigated. This technique was especially useful for a rough surface sample as an alternative to SIMS depth profiling.