Microfabrication of X-ray Optics by Metal Assisted Chemical Etching: A Review

Romano, Lucia; Stampanoni, Marco

doi:10.3390/mi11060589

Cited by 41 publications

(30 citation statements)

References 153 publications

(236 reference statements)

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“…sensors, tissue engineering, and drug delivery), and it is expected to be used for semiconductor microfabrication. [19][20][21][22] Our group has applied the porous Si in solar cells, 5,8,23,24 electroless plating, 25,26 and laser plasma spectroscopy. 27 Meanwhile, it is required to control the etching behavior for the improvement of processing accuracy.…”

Section: Introductionmentioning

confidence: 99%

Formation and Dissolution of Mesoporous Layer during Metal-Particle-Assisted Etching of n-Type Silicon

et al. 2021

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Metal-assisted etching has attracted increasing attention as a method to produce porous silicon (Si). We previously found that gold (Au)-and platinum (Pt)-particle-assisted etching causes general corrosion of the Si substrate, but not in the case of silver (Ag)-particle-assisted etching [A. Matsumoto, et al., RSC Adv., 10, 253 (2020)]. In this work, we discussed the 2 mechanism of the general corrosion with electrochemical approaches. We demonstrated that potentials of the Au-and Pt-deposited Si during the metal-particle-assisted etching are higher than that of the bare Si in the etchant, but not in the case of the Ag-deposited Si. We also performed electrochemical etching of the bare Si by applying the potential during the Pt-particle-assisted etching, resulting in the formation of a mesoporous layer which was dissolved in the etchant. We concluded that the general corrosion occurs during the metal-particle-assisted etching due to the dissolution of the mesoporous layer formed by anodic polarization of the Si substrate.

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Section: Introductionmentioning

confidence: 99%

Formation and Dissolution of Mesoporous Layer during Metal-Particle-Assisted Etching of n-Type Silicon

et al. 2021

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“…Availability of standard lithographic techniques and well-established technologies for silicon microfabrication are additional advantages of this approach, which opens up the route for a cost-efficient production in larger wafer sizes and higher volumes. Several Si-based technologies for the fabrication of metallic X-ray gratings were recently reported: conformal electroplating with partial (also known as spatial frequency doubling technique) [ 12 ] or complete [ 12 , 13 , 14 ] filling; seedless electroplating through a mask [ 15 , 16 ]; metal casting of Bi [ 17 ], as well as of Au [ 18 ] and Pb alloys [ 19 ]; atomic layer deposition (ALD) of Ir [ 20 ]; bottom-up Au electroplating on a metal seed layer [ 21 , 22 , 23 , 24 , 25 ]. Each of the above techniques has its own strengths and weaknesses.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of X-ray Gratings for Interferometric Imaging by Conformal Seedless Gold Electroplating

et al. 2021

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We present a method to produce small pitch gratings for X-ray interferometric imaging applications, allowing the phase sensitivity to be increased and/or the length of the laboratory setup to be minimized. The method is based on fabrication of high aspect ratio silicon microstructures using deep reactive ion etching (Bosch technique) of dense grating arrays and followed by conformal electroplating of Au. We demonstrated that low resistivity Si substrates (<0.01 Ohm·cm) enable the metal seeding layer deposition step to be avoided, which is normally required to initiate the electroplating process. Etching conditions were optimized to realize Si recess structures with a slight bottom tapering, which ensured the void-free Au filling of the trenches. Vapor HF was used to remove the native oxide layer from the Si grating surface prior to electroplating in the cyanide-based Au electrolyte. Fabrication of Au gratings with pitch in the range 1.2–3.0 µm was successfully realized. A substantial improved aspect ratio of 45:1 for a pitch size of 1.2 µm was achieved with respect to the prior art on 4-inch wafer-based technology. The fabricated Au gratings were tested with X-ray interferometers in Talbot–Laue configuration with measured visibility of 13% at an X-ray design energy of 26 keV.

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“…In other words, the conventional pyramidal structure has a limited light trapping performance, and silicon with a regular inverted pyramidal textured film applied can achieve a reflectance of about 14% [ 30 ]. The principle of Metal-assisted chemical etching (MacEtch) is simple [ 31 , 32 , 33 ], Au nano particles (NPs) act as catalysts to induce local oxidation in acidic solutions, forming pores underneath. The corrosion rate of silicon under Au NPs is much higher than that of uncovered silicon in a mixed solution composed of hydrogen peroxide and hydrofluoric acid [ 34 ].…”

Section: Introductionmentioning

confidence: 99%

Fabrication and Characterization of Inverted Silicon Pyramidal Arrays with Randomly Distributed Nanoholes

Zhao

Zhang

et al. 2021

Micromachines

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We report the fabrication, electromagnetic simulation and measurement of inverted silicon pyramidal arrays with randomly distributed nanoholes that act as an anti-reflectivity coating. The fabrication route combines the advantages of anisotropic wet etching and metal-assisted chemical etching. The former is employed to form inverted silicon pyramid arrays, while the latter is used to generate randomly distributed nanoholes on the surface and sidewalls of the generated inverted silicon pyramidal arrays. We demonstrate, numerically and experimentally, that such a structure facilitates the multiple reflection and absorption of photons. The resulting nanostructure can achieve the lowest reflectance of 0.45% at 700 nm and the highest reflectance of 5.86% at 2402 nm. The average reflectance in the UV region (250–400 nm), visible region (400–760 nm) and NIR region (760–2600 nm) are 1.11, 0.63 and 3.76%, respectively. The reflectance at broadband wavelength (250–2600 nm) is 14.4 and 3.4 times lower than silicon wafer and silicon pyramids. In particular, such a structure exhibits high hydrophobicity with a contact angle up to 132.4°. Our method is compatible with well-established silicon planar processes and is promising for practical applications of anti-reflectivity coating.

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Microfabrication of X-ray Optics by Metal Assisted Chemical Etching: A Review

Cited by 41 publications

References 153 publications

Formation and Dissolution of Mesoporous Layer during Metal-Particle-Assisted Etching of n-Type Silicon

Formation and Dissolution of Mesoporous Layer during Metal-Particle-Assisted Etching of n-Type Silicon

Fabrication of X-ray Gratings for Interferometric Imaging by Conformal Seedless Gold Electroplating

Fabrication and Characterization of Inverted Silicon Pyramidal Arrays with Randomly Distributed Nanoholes

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