X-ray Imaging of Functional Three-Dimensional Nanostructures on Massive Substrates

Abstract

To investigate the performance of three-dimensional (3D) nanostructures, it is vital to study their internal structure with a methodology that keeps the device fully functional and ready for further integration. To this aim, we introduce here traceless X-ray tomography (TXT) that combines synchrotron X-ray holographic tomography with high X-ray photon energies (17 keV) in order to study nanostructures “as is” on massive silicon substrates. The combined strengths of TXT are a large total sample size to field-of-view ratio and a large penetration depth. We study exemplary 3D photonic band gap crystals made by CMOS-compatible means and obtain real space 3D density distributions with 55 nm spatial resolution. TXT identifies why nanostructures that look similar in electron microscopy have vastly different nanophotonic functionality: one “good” crystal with a broad photonic gap reveals 3D periodicity as designed; a second “bad” structure without a gap reveals a buried void, and a third “ugly” one without gap is shallow due to fabrication errors. Thus, TXT serves to nondestructively differentiate between the possible reasons of not finding the designed and expected performance and is therefore a powerful tool to critically assess 3D functional nanostructures.

Fast X‐ray Nanotomography with Sub‐10 nm Resolution as a Powerful Imaging Tool for Nanotechnology and Energy Storage Applications

“…However, the best 3D resolution reported so far is 55 nm. [ 24 ] The constant and rapid development of manufactured nanomaterials and the societal and economic stakes associated with them are important drivers for improving the resolving power of X‐ray microscopes. A typical example illustrating this trend is Moore's law for semiconductor and microelectronics industry.…”

“…However, the best 3D resolution reported so far is 55 nm. [24] The constant and rapid development of manufactured nanomaterials and the societal and economic stakes associated with them are important drivers for improving the resolving power of X-ray microscopes.In the last decade, transmission X-ray microscopes (TXMs) have come into operation in most of the synchrotrons worldwide. They have proven to be outstanding tools for non-invasive ex and in situ 3D characterization of materials at the nanoscale across varying range of scientific applications.…”

Three-Dimensional Imaging of Metallic Grain by Stacking the Microscopic Images

“…In addition, residual magnetization is frequently generated in welds where heat and residual stress are generated by an external force. In the eddy current method of inspection, an induced current is applied to an object to be measured, and the distortion of the induced current occurring around a fault, that is, a change in impedance and a different phase due to eddy currents is measured [28,29]. However, it is difficult to determine the presence or size of a defect due to the edge effect that occurs at the end of the object to be measured [30].…”

Targeted positioning of quantum dots inside 3D silicon photonic crystals revealed by synchrotron X-ray fluorescence tomography

“…Such a high photon energy also allows for samples to be integrated on thick substrates like wafers. 40 At the ID16A instrument used in the present study, it is also feasible to excite at an even higher photon energy of 33.5 keV, but this makes little sense since a major limitation is the absorption of the emitted Xray fluorescence that has a fixed energy. Exciting at higher photon energy will reduce the excitation efficiency and therefore also reduce the sensitivity.…”