High-Resolution X-ray Diffraction Based on Refractive Lenses
One of the promising areas of nano- and microelectronics is the development of technologies for the production of 3D small sized semiconductor structures. One example is the detection of electromagnetic radiation by complementary metal oxide semiconductor (CMOS) matrices where millions of pixels (semiconductor heterostructures) are arranged on the substrate. Creating a new, more complex structures with unique properties, as well as the development of production technology, in turn, implies the improvement of methods of their study. The paper presents a method for studying such structures, which allows to exceed the resolution of the classical method of X-ray diffraction.
The method is based on the idea of using X-ray refractive lenses as a Fourier transformer. Thus, the X-ray CCD camera is placed in the image plane of the lens, and the lens itself can be placed before or after the structures under study. In this geometry, the refractive lens acts as a high-resolution analyzer of the wavefront, which is formed as a result of X-ray diffraction on the ordered crystal structures in Bragg geometry. The advantages of the proposed method are as follows: the flexibility of experimental setup; convenience of adjustment and measurement as compared to the classical methods of X-ray diffraction; the possibility of reducing the duration of the experiments; high angular resolution; and the ability to observe the reflection from the crystal in a certain range of incidence angles.
To demonstrate the possibilities of the proposed high-resolution X-ray diffractometry using Fourier optics, experiments using coherent synchrotron radiation source were performed. By means of this method a specially prepared diffractive microstructure were examined. These structures were manufactured on the single-crystal silicon wafer using precision ion beamlithography. In addition, we investigated the Si-Ge nano-heterostructures that are 100 nanometer germanium nano-crystals, standing on a periodic grid of the silicon pillars, with width of 90 nanometers and a height of 150 nanometers. The obtained results allowed to get detailed information on the periodicity, spatial orientation and crystalline perfection of the structures under study.