Transmission Small-angle X-ray Scattering Research Articles

Precise 3D profile determination of high aspect ratio hole patterns by transmission small-angle X-ray scattering

The etching process of high aspect ratio (HAR) hole patterns on a wafer surface is a key step for fabricating new-generation semiconductor memory devices with vertically stacked structures. As the stacking number of these memory devices increases, it is getting more challenging to maintain the ideal etching profile of HAR holes. Therefore, detailed profile evaluation of these HAR holes is increasingly important. In this study, we have measured 4.2 μm deep holes by transmission small-angle X-ray scattering (T-SAXS) to determine the precise three-dimensional (3D) hole profile. By applying an improved 3D shape model for a hole, we successfully determined a hole profile whose cross-section parallel to the sample surface changes from elliptical to rectangular along its depth. This 3D profile measurement demonstrated that T-SAXS has sufficient sensitivity to evaluate a cross-sectional shape change along the depth of HAR holes.

Measurements of an Effective Longitudinal Coherence Length in Transmission Small Angle X-ray Scatterings.

The notion of an effective longitudinal coherence length with its value much greater than has been adopted in small-angle X-ray scattering communities for years, where and denote the incident wavelength and its spread, respectively. Often the implications of the effective longitudinal coherence length do not even enter considerations in the designing and data treatment of small-angle scattering experiments. In this work, conventional transmission small-angle X-ray scattering (tSAXS) was performed to reveal a clear angular dependence on effective longitudinal coherence length. The measured values of effective longitudinal coherence length can be as high as one millimeter, whereas the value of calculated is in nanometers.

In-Situ X-Ray Observations of Sn Electrodeposition into Anodized Alumina

Aluminum is used widely for various products and application because of its characteristics of high strength, low density and good corrosion resistance. When aluminum is exposed to air a native oxide forms on its surface and protects it from corrosion[1,2]. The native oxide can by an electrochemical method called anodization be grown thicker to give a better corrosion protection of the aluminum[3]. By using acidic electrolytes for the anodization the grown oxide will become porous, these pores can become ordered under certain anodization conditions[4]. The grown Nano-Porous Anodic Aluminum Oxide (NP-AAO) can be used as a template for growing nano wires and can be colored by deposition of metals into the pores. We have followed in-situ the electrochemical deposition of Sn into the NP-AAO by Grazing Transmission Small Angle X-Ray Scattering (GTSAXS), X-Ray Fluorescence (XRF) and X-Ray Absorption Near Edge Structure (XANES). A two-step anodization method was used to create the ordered NP-AAO, this is achieved by anodizing the sample in acidic electrolytes in two anodizing steps with a chemical etch between the steps. The second anodization step was followed in-situ with GTSAXS[5]. To achieve a better deposition into the pores of the oxide, either a barrier layer thinning or a pore widening step was used after the second anodization. These methods will decrease the barrier layer at the bottom of the pores by a controlled down stepping of the anodization potential and make the pores wider trough a chemical etch. Both methods were followed continuously by GTSAXS. The electrochemical deposition of Sn was achieved using an alternating voltage and an electrolyte containing tin ions. We followed the deposition continuously with GTSAXS, while XRF and XANES was measured at intervals during the deposition. Our GTSAXS measurements shows an increase in intensity during deposition, indicating deposition into the pores of the aluminum oxide. From our XRF measurements an increase of deposited Sn could be detected as the XRF signal at the sample increased over time. We used XANES for determining the chemical state of the deposited Sn. Ex-situ FIB-SEM measurements shows the pores filled with Sn, confirming the in-situ measurements. The sample also had a change in color confirming the Sn presence inside the NP-AAO. References L.P.H. Jeurgens, W.G. Sloof, F.D. Tichelaar, C.G. Borsboom, E.J. Mittemeijer, Determination of thickness and composition of aluminium-oxide overlayers on aluminium substrates, Appl. Surf. Sci. 144, 11 (1999)J. Evertsson et al, The thickness of native oxides on aluminum alloys and single crystals, Appl.Surf. Sci. 349, 826 (2015)F. Bertram et al, In situ anodization of aluminum surfaces studied by x-ray reflectivity and electrochemical impedance spectroscopy, J. Appl. Phys. 116, 034902, (2014)W. Lee. and S.-J. Park, Porous Anodic Aluminum Oxide: Anodization and Templated Synthesis of Functional Nanostructures, Chem. Rev. 114, 7487 (2014)Nikolay A. Vinogradov, Gary S. Harlow, Francesco Carlà, Jonas Evertsson, Lisa Rullik, Weronica Linpé, Roberto Felici, and Edvin Lundgren, Observation of Pore Growth and Self-Organization in Anodic Alumina by Time-Resolved X-ray Scattering, ACS Applied Nano Materials, Article ASAP

Turning Nano Porous Aluminium Black: An in Situ High-Energy X-Ray Diffraction and X-Ray Fluorescence Study

Anodized aluminum, commonly used everyday applications, is effectively coloured by electro chemical deposition of materials into the nano-porous anodized aluminum oxide (NP-AAO). The colouring process is sensitive to the details of the nano-porous structure, and increased knowledge is essential to increase the effectiveness of the process to prevent cost, time and environmental losses. To study the electro deposition of material into nano-scale objects and coloring as it happens in a harsh electrolyte is notoriously difficult. As a consequence, knowledge about the coloring process has been obtained from time consuming ex-situ studies, in which the composition of the sample may change upon exposure to ambient environments. We have recently performed in situ studies of the formation of ordered NP-AAO using Grazing Transmission Small Angle X-ray Scattering (GTSAXS) [1]. The small x-ray beams produced by modern synchrotron radiation facilities provides the means for non-intrusive X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF) on a micron and sub-micron scale, allowing for high temporal and spatial resolution as the coloring process is occurring. In the present study, we have used micro XRD and XRF to study the electro deposition of Sn into the NP-AAO. An X-ray beam of 5 microns and an energy of 70 keV was used to penetrate the electrolyte and focused on the 20 micron thick layer of NP-AAO. Prior to deposition, the anodized alumina was pre-treated electrochemically in situ using a selected number of chemical procedures. The Sn deposition, which colours the aluminum black, was followed by XRF and initiates at the pore bottom and crystalizes as Sn metal nanowires along the pore height according to XRD.