Fuchs Silvio, Rödel Christian, Blinne Alexander, Zastrau Ulf, Wünsche Martin, Hilbert Vinzenz, Glaser Leif, Viefhaus Jens, Frumker Eugene, Corkum Paul, Förster Eckhart, Paulus Gerhard G
Institute of Optics and Quantum Electronics, Friedrich-Schiller-University Jena, Jena, Germany.
Helmholtz-Institute Jena, Jena, Germany.
Sci Rep. 2016 Feb 10;6:20658. doi: 10.1038/srep20658.
Optical coherence tomography (OCT) is a non-invasive technique for cross-sectional imaging. It is particularly advantageous for applications where conventional microscopy is not able to image deeper layers of samples in a reasonable time, e.g. in fast moving, deeper lying structures. However, at infrared and optical wavelengths, which are commonly used, the axial resolution of OCT is limited to about 1 μm, even if the bandwidth of the light covers a wide spectral range. Here, we present extreme ultraviolet coherence tomography (XCT) and thus introduce a new technique for non-invasive cross-sectional imaging of nanometer structures. XCT exploits the nanometerscale coherence lengths corresponding to the spectral transmission windows of, e.g., silicon samples. The axial resolution of coherence tomography is thus improved from micrometers to a few nanometers. Tomographic imaging with an axial resolution better than 18 nm is demonstrated for layer-type nanostructures buried in a silicon substrate. Using wavelengths in the water transmission window, nanometer-scale layers of platinum are retrieved with a resolution better than 8 nm. XCT as a nondestructive method for sub-surface tomographic imaging holds promise for several applications in semiconductor metrology and imaging in the water window.
光学相干断层扫描（OCT）是一种用于横截面成像的非侵入性技术。对于传统显微镜无法在合理时间内对样品深层进行成像的应用，例如在快速移动、位于较深位置的结构中，它具有特别的优势。然而，在常用的红外和光学波长下，即使光的带宽覆盖很宽的光谱范围，OCT的轴向分辨率也限制在约1微米。在此，我们展示了极紫外相干断层扫描（XCT），从而引入了一种用于纳米结构非侵入性横截面成像的新技术。XCT利用了例如硅样品光谱透射窗口对应的纳米级相干长度。相干断层扫描的轴向分辨率因此从微米提高到了几纳米。对于埋在硅衬底中的层状纳米结构，展示了轴向分辨率优于18纳米的断层成像。使用水透射窗口中的波长，可以以优于8纳米的分辨率获取铂的纳米级层。XCT作为一种用于亚表面断层成像的无损方法，在半导体计量学和水窗成像的多个应用中具有前景。
