1
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Znati S, Wharwood J, Tezanos KG, Li X, Mohseni PK. Metal-assisted chemical etching beyond Si: applications to III-V compounds and wide-bandgap semiconductors. NANOSCALE 2024; 16:10901-10946. [PMID: 38804075 DOI: 10.1039/d4nr00857j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
Metal-assisted chemical etching (MacEtch) has emerged as a versatile technique for fabricating a variety of semiconductor nanostructures. Since early investigations in 2000, research in this field has provided a deeper understanding of the underlying mechanisms of catalytic etching processes and enabled high control over etching conditions for diverse applications. In this Review, we present an overview of recent developments in the application of MacEtch to nanomanufacturing and processing of III-V based semiconductor materials and other materials beyond Si. We highlight the key findings and developments in MacEtch as applied to GaAs, GaN, InP, GaP, InGaAs, AlGaAs, InGaN, InGaP, SiC, β-Ga2O3, and Ge material systems. We further review a series of active and passive devices enabled by MacEtch, including light-emitting diodes (LEDs), field-effect transistors (FETs), optical gratings, sensors, capacitors, photodiodes, and solar cells. By reviewing demonstrated control of morphology, optimization of etch conditions, and catalyst-material combinations, we aim to distill the current understanding of beyond-Si MacEtch mechanisms and to provide a bank of reference recipes to stimulate progress in the field.
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Affiliation(s)
- Sami Znati
- Microsystem Engineering, Rochester Institute of Technology, Rochester, NY 16423, USA.
- NanoPower Research Laboratories, Rochester Institute of Technology, Rochester, NY 14623, USA
| | - Juwon Wharwood
- NanoPower Research Laboratories, Rochester Institute of Technology, Rochester, NY 14623, USA
- Department of Electrical and Computer Engineering, Howard University, Washington, DC 20059, USA
| | - Kyle G Tezanos
- NanoPower Research Laboratories, Rochester Institute of Technology, Rochester, NY 14623, USA
- School of Materials Science and Chemistry, Rochester Institute of Technology, Rochester, NY 14623, USA
| | - Xiuling Li
- Department of Electrical and Computer Engineering, Microelectronics Research Center, The University of Texas at Austin, Austin, TX 78758, USA
| | - Parsian K Mohseni
- Microsystem Engineering, Rochester Institute of Technology, Rochester, NY 16423, USA.
- NanoPower Research Laboratories, Rochester Institute of Technology, Rochester, NY 14623, USA
- School of Materials Science and Chemistry, Rochester Institute of Technology, Rochester, NY 14623, USA
- Department of Electrical and Microelectronic Engineering, Rochester Institute of Technology, Rochester, NY 14623, USA
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2
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Surdo S, Barillaro G. Voltage- and Metal-assisted Chemical Etching of Micro and Nano Structures in Silicon: A Comprehensive Review. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2400499. [PMID: 38644330 DOI: 10.1002/smll.202400499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 03/12/2024] [Indexed: 04/23/2024]
Abstract
Sculpting silicon at the micro and nano scales has been game-changing to mold bulk silicon properties and expand, in turn, applications of silicon beyond electronics, namely, in photonics, sensing, medicine, and mechanics, to cite a few. Voltage- and metal-assisted chemical etching (ECE and MaCE, respectively) of silicon in acidic electrolytes have emerged over other micro and nanostructuring technologies thanks to their unique etching features. ECE and MaCE have enabled the fabrication of novel structures and devices not achievable otherwise, complementing those feasible with the deep reactive ion etching (DRIE) technology, the gold standard in silicon machining. Here, a comprehensive review of ECE and MaCE for silicon micro and nano machining is provided. The chemistry and physics ruling the dissolution of silicon are dissected and similarities and differences between ECE and MaCE are discussed showing that they are the two sides of the same coin. The processes governing the anisotropic etching of designed silicon micro and nanostructures are analyzed, and the modulation of etching profile over depth is discussed. The preparation of micro- and nanostructures with tailored optical, mechanical, and thermo(electrical) properties is then addressed, and their applications in photonics, (bio)sensing, (nano)medicine, and micromechanical systems are surveyed. Eventually, ECE and MaCE are benchmarked against DRIE, and future perspectives are highlighted.
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Affiliation(s)
- Salvatore Surdo
- Dipartimento di Ingegneria dell'Informazione, Università di Pisa, via G. Caruso 16, Pisa, 56122, Italy
| | - Giuseppe Barillaro
- Dipartimento di Ingegneria dell'Informazione, Università di Pisa, via G. Caruso 16, Pisa, 56122, Italy
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3
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Polikarpov M, Vila-Comamala J, Wang Z, Pereira A, van Gogh S, Gasser C, Jefimovs K, Romano L, Varga Z, Lång K, Schmeltz M, Tessarini S, Rawlik M, Jermann E, Lewis S, Yun W, Stampanoni M. Towards virtual histology with X-ray grating interferometry. Sci Rep 2023; 13:9049. [PMID: 37270642 DOI: 10.1038/s41598-023-35854-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Accepted: 05/24/2023] [Indexed: 06/05/2023] Open
Abstract
Breast cancer is the most common type of cancer worldwide. Diagnosing breast cancer relies on clinical examination, imaging and biopsy. A core-needle biopsy enables a morphological and biochemical characterization of the cancer and is considered the gold standard for breast cancer diagnosis. A histopathological examination uses high-resolution microscopes with outstanding contrast in the 2D plane, but the spatial resolution in the third, Z-direction, is reduced. In the present paper, we propose two high-resolution table-top systems for phase-contrast X-ray tomography of soft-tissue samples. The first system implements a classical Talbot-Lau interferometer and allows to perform ex-vivo imaging of human breast samples with a voxel size of 5.57 μm. The second system with a comparable voxel size relies on a Sigray MAAST X-ray source with structured anode. For the first time, we demonstrate the applicability of the latter to perform X-ray imaging of human breast specimens with ductal carcinoma in-situ. We assessed image quality of both setups and compared it to histology. We showed that both setups made it possible to target internal features of breast specimens with better resolution and contrast than previously achieved, demonstrating that grating-based phase-contrast X-ray CT could be a complementary tool for clinical histopathology.
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Affiliation(s)
- M Polikarpov
- Swiss Light Source, Paul Scherrer Institut, 5232, Villigen-PSI, Switzerland.
- Institute for Biomedical Engineering, ETH Zurich, 8092, Zurich, Switzerland.
| | - J Vila-Comamala
- Swiss Light Source, Paul Scherrer Institut, 5232, Villigen-PSI, Switzerland
| | - Z Wang
- Swiss Light Source, Paul Scherrer Institut, 5232, Villigen-PSI, Switzerland
- Institute for Biomedical Engineering, ETH Zurich, 8092, Zurich, Switzerland
- Department of Engineering Physics, Tsinghua University, Haidian District, Beijing, 100080, China
| | - A Pereira
- Swiss Light Source, Paul Scherrer Institut, 5232, Villigen-PSI, Switzerland
- Institute for Biomedical Engineering, ETH Zurich, 8092, Zurich, Switzerland
| | - S van Gogh
- Swiss Light Source, Paul Scherrer Institut, 5232, Villigen-PSI, Switzerland
- Institute for Biomedical Engineering, ETH Zurich, 8092, Zurich, Switzerland
| | - C Gasser
- Institute for Biomedical Engineering, ETH Zurich, 8092, Zurich, Switzerland
| | - K Jefimovs
- Swiss Light Source, Paul Scherrer Institut, 5232, Villigen-PSI, Switzerland
| | - L Romano
- Swiss Light Source, Paul Scherrer Institut, 5232, Villigen-PSI, Switzerland
- Institute for Biomedical Engineering, ETH Zurich, 8092, Zurich, Switzerland
| | - Z Varga
- Department of Pathology and Molecular Pathology, University Hospital Zürich, 8091, Zurich, Switzerland
| | - K Lång
- Department of Diagnostic Radiology, Translational Medicine, Lund University, Lund, Sweden
- Unilabs Mammography Unit, Skåne University Hospital, Malmö, Sweden
| | - M Schmeltz
- Swiss Light Source, Paul Scherrer Institut, 5232, Villigen-PSI, Switzerland
| | - S Tessarini
- Swiss Light Source, Paul Scherrer Institut, 5232, Villigen-PSI, Switzerland
- Institute for Biomedical Engineering, ETH Zurich, 8092, Zurich, Switzerland
| | - M Rawlik
- Swiss Light Source, Paul Scherrer Institut, 5232, Villigen-PSI, Switzerland
- Institute for Biomedical Engineering, ETH Zurich, 8092, Zurich, Switzerland
| | | | - S Lewis
- Sigray Inc., Concord, CA, 94520, USA
| | - W Yun
- Sigray Inc., Concord, CA, 94520, USA
| | - M Stampanoni
- Swiss Light Source, Paul Scherrer Institut, 5232, Villigen-PSI, Switzerland
- Institute for Biomedical Engineering, ETH Zurich, 8092, Zurich, Switzerland
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4
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Ohlin H, Frisk T, Sychugov I, Vogt U. Comparing metal assisted chemical etching of N and P-type silicon nanostructures. MICRO AND NANO ENGINEERING 2023. [DOI: 10.1016/j.mne.2023.100178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
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5
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Pil-Ali A, Adnani S, Karim KS. Self-aligned multi-layer X-ray absorption grating using large-area fabrication methods for X-ray phase-contrast imaging. Sci Rep 2023; 13:2508. [PMID: 36781907 PMCID: PMC9925796 DOI: 10.1038/s41598-023-29580-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 02/07/2023] [Indexed: 02/15/2023] Open
Abstract
X-ray phase-contrast (XPCi) imaging methods are an emerging medical imaging approach that provide significantly better soft tissue contrast and could function as a viable extension to conventional X-ray, CT, and even some MRI. Absorption gratings play a central role in grating-based XPCi systems, especially because they enable the acquisition of three images in a single exposure: transmission, refraction, and dark-field. An impediment to commercial development and adoption of XPCi imaging systems is the lack of large area, high aspect ratio absorption gratings. Grating technology development, primarily due to technological limitations, has lagged system development and today prevents the scaling up of XPCi system into a footprint and price point acceptable to the medical market. In this work, we report on a self-aligned multi-layer grating fabrication process that can enable large-area X-ray absorption gratings with micron-scale feature sizes. We leverage large-area fabrication techniques commonly employed by the thin-film transistor (TFT) display industry. Conventional ITO-on-glass substrates are used with a patterned film of Cr/Au/Cr that serves as a self-aligned lithography mask for backside exposure. Commonly available SU-8 photoresist is patterned using the backside exposure mask followed by an electroplating step to fill the gaps in the SU-8 with X-ray attenuating material. Consequently, the electroplated patterned material acts as a self-aligned photomask for subsequent SU-8 layer patterning and so forth. The repeatability of the reported process makes it suitable for achieving higher aspect ratio structures and is advantageous over previously reported X-ray LIGA approaches. A prototype three-layer grating, with a thickness of around [Formula: see text], having a visibility of 0.28 at [Formula: see text] with a [Formula: see text] active area was fabricated on a 4-inch glass substrate and demonstrated by modifying a commercially available 3D propagation-based XPCi Microscope. The scalable and cost-effective approach to build larger area X-ray gratings reported in this work can help expedite the commercial development and adoption of previously reported Talbot-Lau, speckle-tracking, as well as coded-aperture XPCi systems for large-area clinical and industrial applications.
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Affiliation(s)
- Abdollah Pil-Ali
- Department of Electrical and Computer Engineering, University of Waterloo, 200 University Ave W, Waterloo, ON, N2L3G1, Canada. .,Centre for Bioengineering and Biotechnology, University of Waterloo, 200 University Ave W, Waterloo, ON, N2L3G1, Canada.
| | - Sahar Adnani
- grid.46078.3d0000 0000 8644 1405Department of Electrical and Computer Engineering, University of Waterloo, 200 University Ave W, Waterloo, ON N2L3G1 Canada ,grid.46078.3d0000 0000 8644 1405Centre for Bioengineering and Biotechnology, University of Waterloo, 200 University Ave W, Waterloo, ON N2L3G1 Canada
| | - Karim S. Karim
- grid.46078.3d0000 0000 8644 1405Department of Electrical and Computer Engineering, University of Waterloo, 200 University Ave W, Waterloo, ON N2L3G1 Canada ,grid.46078.3d0000 0000 8644 1405Centre for Bioengineering and Biotechnology, University of Waterloo, 200 University Ave W, Waterloo, ON N2L3G1 Canada
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6
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Zhang X, Yao C, Niu J, Li H, Xie C. Wafer-Scale Fabrication of Ultra-High Aspect Ratio, Microscale Silicon Structures with Smooth Sidewalls Using Metal Assisted Chemical Etching. MICROMACHINES 2023; 14:179. [PMID: 36677239 PMCID: PMC9865805 DOI: 10.3390/mi14010179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 01/07/2023] [Accepted: 01/09/2023] [Indexed: 06/17/2023]
Abstract
Silicon structures with ultra-high aspect ratios have great potential applications in the fields of optoelectronics and biomedicine. However, the slope and increased roughness of the sidewalls inevitably introduced during the use of conventional etching processes (e.g., Bosch and DRIE) remain an obstacle to their application. In this paper, 4-inch wafer-scale, ultra-high aspect ratio (>140:1) microscale silicon structures with smooth sidewalls are successfully prepared using metal-assisted chemical etching (MacEtch). Here, we clarify the impact of the size from the metal catalytic structure on the sidewall roughness. By optimizing the etchant ratio to accelerate the etch rate of the metal-catalyzed structure and employing thermal oxidation, the sidewall roughness can be significantly reduced (average root mean square (RMS) from 42.3 nm to 15.8 nm). Simulations show that a maximum exciton production rate (Gmax) of 1.21 × 1026 and a maximum theoretical short-circuit current density (Jsc) of 39.78 mA/cm2 can be obtained for the micropillar array with smooth sidewalls, which have potential applications in high-performance microscale photovoltaic devices.
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Affiliation(s)
- Xiaomeng Zhang
- Key Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Chuhao Yao
- Key Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jiebin Niu
- Key Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029, China
| | - Hailiang Li
- Key Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029, China
| | - Changqing Xie
- Key Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029, China
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7
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Chen X, Jiang S, Li Y, Jiang Y, Wang W. Fabrication of ultra-high aspect ratio silicon grating using an alignment method based on a scanning beam interference lithography system. OPTICS EXPRESS 2022; 30:40842-40853. [PMID: 36299010 DOI: 10.1364/oe.469374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 08/11/2022] [Indexed: 06/16/2023]
Abstract
The high-aspect-ratio silicon grating (HARSG) is an important X-ray optical device that is widely used in X-ray imaging and spectrum detection systems. In this paper, we propose a high-precision alignment method based on the scanning beam interference lithography (SBIL) system to realize precise alignment between the <111> orientation on the (110) wafer plane and the grating lines direction, which is an essential step in HARSG manufacture to obtain the high-aspect-ratio grating structure. After the location of the <111> orientation through fan-shaped mask etching and reference grating fabrication, a two-step method that combines static preliminary alignment and dynamic precision alignment is used to align the reference grating lines direction with the interference field fringes of the SBIL system through the interference of the diffracted light from the reference grating near the normal direction, which can realize a minimal alignment error of 0.001°. Through the overall alignment process, HARSGs with groove densities of 500 gr/mm, 1800 gr/mm, and 3600 gr/mm were fabricated through anisotropic wet etching in KOH solution, producing ultra-high aspect ratios and etch rate ratios greater than 200.
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8
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Sharstniou A, Niauzorau S, Hardison AL, Puckett M, Krueger N, Ryckman JD, Azeredo B. Roughness Suppression in Electrochemical Nanoimprinting of Si for Applications in Silicon Photonics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2206608. [PMID: 36075876 DOI: 10.1002/adma.202206608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 08/29/2022] [Indexed: 06/15/2023]
Abstract
Metal-assisted electrochemical nanoimprinting (Mac-Imprint) scales the fabrication of micro- and nanoscale 3D freeform geometries in silicon and holds the promise to enable novel chip-scale optics operating at the near-infrared spectrum. However, Mac-Imprint of silicon concomitantly generates mesoscale roughness (e.g., protrusion size ≈45 nm) creating prohibitive levels of light scattering. This arises from the requirement to coat stamps with nanoporous gold catalyst that, while sustaining etchant diffusion, imprints its pores (e.g., average diameter ≈42 nm) onto silicon. In this work, roughness is reduced to sub-10 nm levels, which is in par with plasma etching, by decreasing pore size of the catalyst via dealloying in far-from equilibrium conditions. At this level, single-digit nanometric details such as grain-boundary grooves of the catalyst are imprinted and attributed to the resolution limit of Mac-Imprint, which is argued to be twice the Debye length (i.e., 1.7 nm)-a finding that broadly applies to metal-assisted chemical etching. Last, Mac-Imprint is employed to produce single-mode rib-waveguides on pre-patterned silicon-on-insulator wafers with root-mean-square line-edge roughness less than 10 nm while providing depth uniformity (i.e., 42.9 ± 5.5 nm), and limited levels of silicon defect formation (e.g., Raman peak shift < 0.1 cm-1 ) and sidewall scattering.
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Affiliation(s)
- Aliaksandr Sharstniou
- Arizona State University, School of Manufacturing Systems and Networks, 6075 S. Innovation Way West, Mesa, AZ, 85212, USA
| | - Stanislau Niauzorau
- Arizona State University, School of Manufacturing Systems and Networks, 6075 S. Innovation Way West, Mesa, AZ, 85212, USA
| | - Anna L Hardison
- Clemson University, Holcombe Department of Electrical and Computer Engineering, 91 Technology Drive, Anderson, SC, 29625, USA
| | - Matthew Puckett
- Honeywell International, Aerospace Advanced Technology Advanced Sensors & Microsystems, 21111 N. 19th Avenue, Phoenix, AZ, 85027, USA
| | - Neil Krueger
- Honeywell International, Aerospace Advanced Technology Advanced Sensors & Microsystems, 12001 State Highway 55, Plymouth, MN, 55441, USA
| | - Judson D Ryckman
- Clemson University, Holcombe Department of Electrical and Computer Engineering, 91 Technology Drive, Anderson, SC, 29625, USA
| | - Bruno Azeredo
- Arizona State University, School of Manufacturing Systems and Networks, 6075 S. Innovation Way West, Mesa, AZ, 85212, USA
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9
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Fabrication of X-ray absorption gratings by centrifugal deposition of bimodal tungsten particles in high aspect ratio silicon templates. Sci Rep 2022; 12:5405. [PMID: 35354819 PMCID: PMC8968707 DOI: 10.1038/s41598-022-08222-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 03/03/2022] [Indexed: 11/08/2022] Open
Abstract
Grating-based X-ray imaging employs high aspect ratio absorption gratings to generate contrast induced by attenuating, phase-shifting, and small-angle scattering properties of the imaged object. The fabrication of the absorption gratings remains a crucial challenge of the method on its pathway to clinical applications. We explore a simple and fast centrifugal tungsten particle deposition process into silicon-etched grating templates, which has decisive advantages over conventional methods. For that, we use a bimodal tungsten particle suspension which is introduced into a custom designed grating holder and centrifuged at over 1000×g. Gratings with 45 µm period, 450 µm depth, and 170 mm × 38 mm active area are successfully processed reaching a homogeneous absorber filling. The effective absorbing tungsten thickness in the trenches is 207 µm resulting in a filling ratio of 46.6% compared to a voidless filling. The grating was tested in a Talbot–Lau interferometer designed for clinical X-ray dark-field computed tomography, where visibilities up to 33.6% at 60 kV were achieved.
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10
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Hönicke P, Kayser Y, Nikolaev KV, Soltwisch V, Scheerder JE, Fleischmann C, Siefke T, Andrle A, Gwalt G, Siewert F, Davis J, Huth M, Veloso A, Loo R, Skroblin D, Steinert M, Undisz A, Rettenmayr M, Beckhoff B. Simultaneous Dimensional and Analytical Characterization of Ordered Nanostructures. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2105776. [PMID: 34821030 DOI: 10.1002/smll.202105776] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 10/20/2021] [Indexed: 06/13/2023]
Abstract
The spatial and compositional complexity of 3D structures employed in today's nanotechnologies has developed to a level at which the requirements for process development and control can no longer fully be met by existing metrology techniques. For instance, buried parts in stratified nanostructures, which are often crucial for device functionality, can only be probed in a destructive manner in few locations as many existing nondestructive techniques only probe the objects surfaces. Here, it is demonstrated that grazing exit X-ray fluorescence can simultaneously characterize an ensemble of regularly ordered nanostructures simultaneously with respect to their dimensional properties and their elemental composition. This technique is nondestructive and compatible to typically sized test fields, allowing the same array of structures to be studied by other techniques. For crucial parameters, the technique provides sub-nm discrimination capabilities and it does not require access-limited large-scale research facilities as it is compatible to laboratory-scale instrumentation.
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Affiliation(s)
- Philipp Hönicke
- Div. 7 - Temperature and Synchrotron Radiation, Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587, Berlin, Germany
| | - Yves Kayser
- Div. 7 - Temperature and Synchrotron Radiation, Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587, Berlin, Germany
| | | | - Victor Soltwisch
- Div. 7 - Temperature and Synchrotron Radiation, Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587, Berlin, Germany
| | | | - Claudia Fleischmann
- imec, Kapeldreef 75, Leuven, 3001, Belgium
- Quantum Solid-State Physics, KU Leuven, Celestijnenlaan 200D, Leuven, 3001, Belgium
| | - Thomas Siefke
- Abbe Center of Photonics, Friedrich Schiller University Jena, Max-Wien-Platz 1, 07745, Jena, Germany
| | - Anna Andrle
- Div. 7 - Temperature and Synchrotron Radiation, Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587, Berlin, Germany
| | - Grzegorz Gwalt
- Helmholtz Zentrum Berlin für Materialien und Energie (HZB), Albert-Einstein-Str. 15, 12489, Berlin, Germany
| | - Frank Siewert
- Helmholtz Zentrum Berlin für Materialien und Energie (HZB), Albert-Einstein-Str. 15, 12489, Berlin, Germany
| | - Jeffrey Davis
- EOS GmbH, Robert-Stirling-Ring 1, 82152, Krailling, Germany
| | - Martin Huth
- PNDetector GmbH, Otto-Hahn-Ring 6, 81739, München, Germany
| | - Anabela Veloso
- Quantum Solid-State Physics, KU Leuven, Celestijnenlaan 200D, Leuven, 3001, Belgium
| | - Roger Loo
- Quantum Solid-State Physics, KU Leuven, Celestijnenlaan 200D, Leuven, 3001, Belgium
| | - Dieter Skroblin
- Div. 7 - Temperature and Synchrotron Radiation, Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587, Berlin, Germany
| | - Michael Steinert
- Abbe Center of Photonics, Friedrich Schiller University Jena, Max-Wien-Platz 1, 07745, Jena, Germany
| | - Andreas Undisz
- Technische Universität Chemnitz, Inst. für Werkstoffwiss. und Werkstofftech., Erfenschlager Straße 73, 09125, Chemnitz, Germany
| | - Markus Rettenmayr
- Otto Schott Institute of Materials Research, Friedrich Schiller University Jena, Löbdergraben 32, 07743, Jena, Germany
| | - Burkhard Beckhoff
- Div. 7 - Temperature and Synchrotron Radiation, Physikalisch-Technische Bundesanstalt (PTB), Abbestr. 2-12, 10587, Berlin, Germany
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11
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Bian C, Zhang B, Zhang Z, Chen H, Zhang D, Wang S, Ye J, He L, Jie J, Zhang X. Wafer-Scale Fabrication of Silicon Nanocones via Controlling Catalyst Evolution in All-Wet Metal-Assisted Chemical Etching. ACS OMEGA 2022; 7:2234-2243. [PMID: 35071912 PMCID: PMC8772306 DOI: 10.1021/acsomega.1c05790] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2021] [Accepted: 12/23/2021] [Indexed: 06/14/2023]
Abstract
All-wet metal-assisted chemical etching (MACE) is a simple and low-cost method to fabricate one-dimensional Si nanostructures. However, it remains a challenge to fabricate Si nanocones (SiNCs) with this method. Here, we achieved wafer-scale fabrication of SiNC arrays through an all-wet MACE process. The key to fabricate SiNCs is to control the catalyst evolution from deposition to etching stages. Different from conventional MACE processes, large-size Ag particles by solution deposition are obtained through increasing AgNO3 concentration or extending the reaction time in the seed solution. Then, the large-size Ag particles are simultaneously etched during the Si etching process in an etching solution with a high H2O2 concentration due to the accelerated cathode process and inhibited anode process in Ag/Si microscopic galvanic cells. The successive decrease of Ag particle sizes causes the proportionate increase of diameters of the etched Si nanostructures, forming SiNC arrays. The SiNC arrays exhibit a stronger light-trapping ability and better photoelectrochemical performance compared with Si nanowire arrays. SiNCs were fabricated by using n-type 1-10 Ω cm Si(100) wafers in this work. Though the specific experimental conditions for preparing SiNCs may differ when using different Si wafers, the summarized diagram will still provide valuable guidance for morphology control of Si nanostructures in MACE processes.
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Affiliation(s)
- Chenyu Bian
- Institute
of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory
for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou 215123, Jiangsu, People’s
Republic of China
| | - Bingchang Zhang
- School
of Optoelectronic Science and Engineering, Key Laboratory of Advanced
Optical Manufacturing Technologies of Jiangsu Province, Key Laboratory of Modern Optical Technologies of Education
Ministry of China, Suzhou 215123, Jiangsu, People’s
Republic of China
| | - Zhenghe Zhang
- School
of Optoelectronic Science and Engineering, Key Laboratory of Advanced
Optical Manufacturing Technologies of Jiangsu Province, Key Laboratory of Modern Optical Technologies of Education
Ministry of China, Suzhou 215123, Jiangsu, People’s
Republic of China
| | - Hui Chen
- School
of Optoelectronic Science and Engineering, Key Laboratory of Advanced
Optical Manufacturing Technologies of Jiangsu Province, Key Laboratory of Modern Optical Technologies of Education
Ministry of China, Suzhou 215123, Jiangsu, People’s
Republic of China
| | - Dake Zhang
- Institute
of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory
for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou 215123, Jiangsu, People’s
Republic of China
| | - Shaojun Wang
- School
of Optoelectronic Science and Engineering, Key Laboratory of Advanced
Optical Manufacturing Technologies of Jiangsu Province, Key Laboratory of Modern Optical Technologies of Education
Ministry of China, Suzhou 215123, Jiangsu, People’s
Republic of China
| | - Jing Ye
- Testing
& Analysis Center, Soochow University, Suzhou 215123, Jiangsu, People’s Republic of China
| | - Le He
- Institute
of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory
for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou 215123, Jiangsu, People’s
Republic of China
| | - Jiansheng Jie
- Institute
of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory
for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou 215123, Jiangsu, People’s
Republic of China
- Macao
Institute of Materials Science and Engineering, Macau University of
Science and Technology, Taipa 999078, Macau SAR, People’s
Republic of China
| | - Xiaohong Zhang
- Institute
of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory
for Carbon-Based Functional Materials & Devices, Soochow University, Suzhou 215123, Jiangsu, People’s
Republic of China
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12
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Srivastava RP, Khang DY. Structuring of Si into Multiple Scales by Metal-Assisted Chemical Etching. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2005932. [PMID: 34013605 DOI: 10.1002/adma.202005932] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 11/18/2020] [Indexed: 05/27/2023]
Abstract
Structuring Si, ranging from nanoscale to macroscale feature dimensions, is essential for many applications. Metal-assisted chemical etching (MaCE) has been developed as a simple, low-cost, and scalable method to produce structures across widely different dimensions. The process involves various parameters, such as catalyst, substrate doping type and level, crystallography, etchant formulation, and etch additives. Careful optimization of these parameters is the key to the successful fabrication of Si structures. In this review, recent additions to the MaCE process are presented after a brief introduction to the fundamental principles involved in MaCE. In particular, the bulk-scale structuring of Si by MaCE is summarized and critically discussed with application examples. Various approaches for effective mass transport schemes are introduced and discussed. Further, the fine control of etch directionality and uniformity, and the suppression of unwanted side etching are also discussed. Known application examples of Si macrostructures fabricated by MaCE, though limited thus far, are presented. There are significant opportunities for the application of macroscale Si structures in different fields, such as microfluidics, micro-total analysis systems, and microelectromechanical systems, etc. Thus more research is necessary on macroscale MaCE of Si and their applications.
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Affiliation(s)
- Ravi P Srivastava
- Soft Electronic Materials and Devices Laboratory, Department of Materials Science and Engineering, Yonsei University, Seoul, 03722, Korea
| | - Dahl-Young Khang
- Soft Electronic Materials and Devices Laboratory, Department of Materials Science and Engineering, Yonsei University, Seoul, 03722, Korea
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13
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Akan R, Vogt U. Optimization of Metal-Assisted Chemical Etching for Deep Silicon Nanostructures. NANOMATERIALS (BASEL, SWITZERLAND) 2021; 11:2806. [PMID: 34835572 PMCID: PMC8619014 DOI: 10.3390/nano11112806] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 10/13/2021] [Accepted: 10/19/2021] [Indexed: 11/21/2022]
Abstract
High-aspect ratio silicon (Si) nanostructures are important for many applications. Metal-assisted chemical etching (MACE) is a wet-chemical method used for the fabrication of nanostructured Si. Two main challenges exist with etching Si structures in the nanometer range with MACE: keeping mechanical stability at high aspect ratios and maintaining a vertical etching profile. In this work, we investigated the etching behavior of two zone plate catalyst designs in a systematic manner at four different MACE conditions as a function of mechanical stability and etching verticality. The zone plate catalyst designs served as models for Si nanostructures over a wide range of feature sizes ranging from 850 nm to 30 nm at 1:1 line-to-space ratio. The first design was a grid-like, interconnected catalyst (brick wall) and the second design was a hybrid catalyst that was partly isolated, partly interconnected (fishbone). Results showed that the brick wall design was mechanically stable up to an aspect ratio of 30:1 with vertical Si structures at most investigated conditions. The fishbone design showed higher mechanical stability thanks to the Si backbone in the design, but on the other hand required careful control of the reaction kinetics for etching verticality. The influence of MACE reaction kinetics was identified by lowering the oxidant concentration, lowering the processing temperature and by isopropanol addition. We report an optimized MACE condition to achieve an aspect ratio of at least 100:1 at room temperature processing by incorporating isopropanol in the etching solution.
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Affiliation(s)
- Rabia Akan
- KTH Royal Institute of Technology, Department of Applied Physics, Albanova University Center, 106 91 Stockholm, Sweden
| | - Ulrich Vogt
- KTH Royal Institute of Technology, Department of Applied Physics, Albanova University Center, 106 91 Stockholm, Sweden
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14
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Fabrication and Characterization of Inverted Silicon Pyramidal Arrays with Randomly Distributed Nanoholes. MICROMACHINES 2021; 12:mi12080931. [PMID: 34442553 PMCID: PMC8400036 DOI: 10.3390/mi12080931] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 08/02/2021] [Accepted: 08/03/2021] [Indexed: 11/29/2022]
Abstract
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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15
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Shi Z, Jefimovs K, Romano L, Vila-Comamala J, Stampanoni M. Laboratory X-ray interferometry imaging with a fan-shaped source grating. OPTICS LETTERS 2021; 46:3693-3696. [PMID: 34329258 DOI: 10.1364/ol.426867] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 06/28/2021] [Indexed: 06/13/2023]
Abstract
The orientation mismatch between the cone beam of an X-ray tube and the grating lines in a flat substrate remains a big challenge for laboratory grating-based X-ray interferometry, since it severely limits the imaging field of view. Here, we fabricated fan-shaped G0 source gratings by modulating the electric field during the deep reactive ion etching of silicon. The gold electroplated fan-shaped G0 grating (3.0 µm pitch) in a 20 keV interferometer improves the uniformity of the field of view with an increase of average visibility from 16.2% to 18.5% and a better angular sensitivity (by a factor 5.8) at the edges.
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16
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Gayrard M, Voronkoff J, Boissière C, Montero D, Rozes L, Cattoni A, Peron J, Faustini M. Replacing Metals with Oxides in Metal-Assisted Chemical Etching Enables Direct Fabrication of Silicon Nanowires by Solution Processing. NANO LETTERS 2021; 21:2310-2317. [PMID: 33600718 DOI: 10.1021/acs.nanolett.1c00178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Metal-assisted chemical etching (MACE) has emerged as an effective method to fabricate high aspect ratio nanostructures. This method requires a catalytic mask that is generally composed of a metal. Here, we challenge the general view that the catalyst needs to be a metal by introducing oxide-assisted chemical etching (OACE). We perform etching with metal oxides such as RuO2 and IrO2 by transposing materials used in electrocatalysis to nanofabrication. These oxides can be solution-processed as polymers exhibiting similar capabilities of metals for MACE. Nanopatterned oxides can be obtained by direct nanoimprint lithography or block-copolymer lithography from chemical solution on a large scale. High aspect ratio silicon nanostructures were obtained at the sub-20 nm scale exclusively by cost-effective solution processing by halving the number of fabrication steps compared to MACE. In general, OACE is expected to stimulate new fundamental research on chemical etching assisted by other materials, providing new possibilities for device fabrication.
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Affiliation(s)
- Maxime Gayrard
- Laboratoire Chimie de la Matière Condensée de Paris (LCMCP), Collège de France, CNRS, Sorbonne Université, F-75005 Paris, France
| | - Justine Voronkoff
- Laboratoire Chimie de la Matière Condensée de Paris (LCMCP), Collège de France, CNRS, Sorbonne Université, F-75005 Paris, France
| | - Cédric Boissière
- Laboratoire Chimie de la Matière Condensée de Paris (LCMCP), Collège de France, CNRS, Sorbonne Université, F-75005 Paris, France
| | - David Montero
- Institut des Matériaux de Paris Centre (IMPC FR 2482), Sorbonne Université, UFR de Chimie Campus Jussieu, 75252 Paris, France
| | - Laurence Rozes
- Laboratoire Chimie de la Matière Condensée de Paris (LCMCP), Collège de France, CNRS, Sorbonne Université, F-75005 Paris, France
| | - Andrea Cattoni
- Centre de Nanosciences et de Nanotechnologies (C2N), CNRS UMR 9001, Université Paris-Saclay, 91120 Palaiseau, France
| | - Jennifer Peron
- ITODYS, CNRS, UMR 7086, Université de Paris, 15 Rue J-A de Baïf, F-75013 Paris, France
| | - Marco Faustini
- Laboratoire Chimie de la Matière Condensée de Paris (LCMCP), Collège de France, CNRS, Sorbonne Université, F-75005 Paris, France
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17
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Mallavarapu A, Ajay P, Barrera C, Sreenivasan SV. Ruthenium-Assisted Chemical Etching of Silicon: Enabling CMOS-Compatible 3D Semiconductor Device Nanofabrication. ACS APPLIED MATERIALS & INTERFACES 2021; 13:1169-1177. [PMID: 33348977 DOI: 10.1021/acsami.0c17011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The semiconductor industry's transition to three-dimensional (3D) logic and memory devices has revealed the limitations of plasma etching in reliable creation of vertical high aspect ratio (HAR) nanostructures. Metal-assisted chemical etch (MacEtch) can create ultra-HAR, taper-free nanostructures in silicon, but the catalyst used for reliable MacEtch-gold-is not CMOS (complementary metal-oxide-semiconductor)-compatible and therefore cannot be used in the semiconductor industry. Here, for the first time, we report a ruthenium MacEtch process that is comparable in quality to gold MacEtch. We introduce new process variables-catalyst plasma pretreatment and surface area-to achieve this result. Ruthenium is particularly desirable as it is not only CMOS-compatible but has also been introduced in semiconductor fabrication as an interconnect material. The results presented here remove a significant barrier to adoption of MacEtch for scalable fabrication of 3D semiconductor devices, sensors, and biodevices that can benefit from production in CMOS foundries.
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Affiliation(s)
- Akhila Mallavarapu
- NASCENT Engineering Research Center, University of Texas at Austin, Austin, Texas 78758, United States
| | - Paras Ajay
- NASCENT Engineering Research Center, University of Texas at Austin, Austin, Texas 78758, United States
| | - Crystal Barrera
- NASCENT Engineering Research Center, University of Texas at Austin, Austin, Texas 78758, United States
| | - S V Sreenivasan
- NASCENT Engineering Research Center, University of Texas at Austin, Austin, Texas 78758, United States
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18
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Jo JS, Choi J, Lee SH, Song C, Noh H, Jang JW. Mass Fabrication of 3D Silicon Nano-/Microstructures by Fab-Free Process Using Tip-Based Lithography. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e2005036. [PMID: 33369134 DOI: 10.1002/smll.202005036] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 11/26/2020] [Indexed: 06/12/2023]
Abstract
Methods for the mass fabrication of 3D silicon (Si) microstructures with a 100 nm resolution are developed using scanning probe lithography (SPL) combined with metal-assisted chemical etching (MACE). Protruding Si structures, including Si nanowires of over 10 µm in length and atypical shaped Si nano- and micropillars, are obtained via the MACE of a patterned gold film (negative tone) on Si substrates by dip-pen nanolithography (DPN) with polymer or by nanoshaving alkanethiol self-assembled monolayers (SAMs). Furthermore, recessed Si structures with arbitrary patterning and channels less than 160 nm wide and hundreds of nanometers in depth are obtained via the MACE of a patterned gold film (positive tone) on Si substrates by alkanethiol DPN. As an example of applications using protruded Si structures, nanoimprinting in an area of up to a centimeter is demonstrated through 1D and 2D SPL combined with MACE. Similarly, submicrometer polydimethylsiloxane (PDMS) stamps are employed over millimeter-scale areas for applications using recessed Si structures. In particular, the mass production of arbitrarily shaped Si microparticles at submicrometer resolution is developed using silicon-on-insulator substrates, as demonstrated using optical microresonators, surface-enhanced Raman scattering templates, and smart microparticles for fluorescence signal coding.
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Affiliation(s)
- Jeong-Sik Jo
- Division of Physics and Semiconductor Science, Dongguk University, Seoul, 04620, Republic of Korea
| | - Jihoon Choi
- Department of Nano and Electronic Physics, Kookmin University, Seoul, 02707, Republic of Korea
| | - Seung-Hoon Lee
- Department of Chemistry, Duke University, Durham, NC, 27708, USA
| | - Changhoon Song
- Department of Physics, Pukyong National University, Busan, 48513, Republic of Korea
| | - Heeso Noh
- Department of Nano and Electronic Physics, Kookmin University, Seoul, 02707, Republic of Korea
| | - Jae-Won Jang
- Division of Physics and Semiconductor Science, Dongguk University, Seoul, 04620, Republic of Korea
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19
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Josell D, Shi Z, Jefimovs K, Guzenko V, Beauchamp C, Peer L, Polikarpov M, Moffat T. Bottom-Up Gold Filling in New Geometries and Yet Higher Aspect Ratio Gratings for Hard X-Ray Interferometry. JOURNAL OF THE ELECTROCHEMICAL SOCIETY 2021; 168:10.1149/1945-7111/ac1d7e. [PMID: 36938320 PMCID: PMC10020954 DOI: 10.1149/1945-7111/ac1d7e] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
An extreme bottom-up filling variant of superconformal Au electrodeposition yielding void-free filling of recessed features is demonstrated with diffraction gratings composed of a two-dimensional patterned "chessboard" array of square vias of aspect ratio (depth/width) ≈ 23 as well as one-dimensional arrays of trenches having aspect ratios exceeding 50 and 65. Deposition on planar and patterned substrates is examined in several near-neutral x mol·L-1 Na3Au(SO3)2 + 0.64 mol·L-1 Na2SO3 electrolytes (x = [0.08, 0.16, 0.32]) containing ≈ 50 μmol·L-1 Bi3+ additive. The electrolytes are similar to those used in earlier work, although the upper bound on Au(SO3)2 concentration is twofold greater than previously described. Filling results are complemented by associated current and deposition charge transients whose features, particularly with well controlled pH, exhibit repeatable behaviors and timescales for incubation of passive deposition followed by bottom-up, void-free filling. While incompletely filled features can exhibit substantial via-to-via variation in fill height, self-passivation that follows complete bottom-up filling results in highly uniform filling profiles across the substrates. Visibility measurements capture the quality and uniformity of the as-formed wafer scale gratings. X-ray phase contrast imaging demonstrates their potential for imaging applications.
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Affiliation(s)
- D. Josell
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - Z. Shi
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
- Institute for Biomedical Engineering, University and ETH Zürich, Zürich 8092, Switzerland
| | - K. Jefimovs
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
- Institute for Biomedical Engineering, University and ETH Zürich, Zürich 8092, Switzerland
| | - V. Guzenko
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
| | - C. Beauchamp
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
| | - L. Peer
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
- Institute for Biomedical Engineering, University and ETH Zürich, Zürich 8092, Switzerland
| | - M. Polikarpov
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
- Institute for Biomedical Engineering, University and ETH Zürich, Zürich 8092, Switzerland
| | - T.P. Moffat
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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20
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Kirchner R, Neumann V, Winkler F, Strobel C, Völkel S, Hiess A, Kazazis D, Künzelmann U, Bartha JW. Anisotropic Etching of Pyramidal Silica Reliefs with Metal Masks and Hydrofluoric Acid. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e2002290. [PMID: 33015964 DOI: 10.1002/smll.202002290] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 07/15/2020] [Indexed: 06/11/2023]
Abstract
This work describes the fabrication of anisotropically etched, faceted pyramidal structures in amorphous layers of silicon dioxide or glass. Anisotropic and crystal-oriented etching of silicon is well known. Anisotropic etching behavior in completely amorphous layers of silicon dioxide in combination with purely isotropic hydrofluoric acid as etchant is an unexpected phenomenon. The work presents practical exploitations of this new process for self-perfecting pyramidal structures. It can be used for textured silica or glass surfaces. The reason for the observed anisotropy, leading to enhanced lateral etch rates, is the presence of thin metal layers. The lateral etch rate under the metal significantly exceeds the vertical etch rate of the non-metallized area by a factor of about 6-43 for liquid and 59 for vapor-based processes. The ratio between lateral and vertical etch rate, thus the sidewall inclination, can be controlled by etchant concentration and selected metal. The described process allows for direct fabrication of shallow angle pyramids, which for example can enhance the coupling efficiency of light emitting diodes or solar cells, can be exploited for producing dedicated silicon dioxide atomic force microscopy tips with a radius in the 50 nm range, or can potentially be used for surface plasmonics.
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Affiliation(s)
- Robert Kirchner
- Institute of Semiconductors and Microsystems, Technische Universität Dresden, Dresden, 01062, Germany
| | - Volker Neumann
- Institute of Semiconductors and Microsystems, Technische Universität Dresden, Dresden, 01062, Germany
| | - Felix Winkler
- Institute of Semiconductors and Microsystems, Technische Universität Dresden, Dresden, 01062, Germany
| | - Carsten Strobel
- Institute of Semiconductors and Microsystems, Technische Universität Dresden, Dresden, 01062, Germany
| | - Sandra Völkel
- Institute of Semiconductors and Microsystems, Technische Universität Dresden, Dresden, 01062, Germany
| | - André Hiess
- Institute of Semiconductors and Microsystems, Technische Universität Dresden, Dresden, 01062, Germany
| | - Dimitrios Kazazis
- Paul Scherrer Institute, Laboratory for Micro- and Nanotechnology, Villigen, PSI 5232, Switzerland
| | - Ulrich Künzelmann
- Institute of Semiconductors and Microsystems, Technische Universität Dresden, Dresden, 01062, Germany
| | - Johann Wolfgang Bartha
- Institute of Semiconductors and Microsystems, Technische Universität Dresden, Dresden, 01062, Germany
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21
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Shi Z, Jefimovs K, Romano L, Stampanoni M. Towards the Fabrication of High-Aspect-Ratio Silicon Gratings by Deep Reactive Ion Etching. MICROMACHINES 2020; 11:E864. [PMID: 32961900 PMCID: PMC7570153 DOI: 10.3390/mi11090864] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 09/10/2020] [Accepted: 09/17/2020] [Indexed: 01/02/2023]
Abstract
The key optical components of X-ray grating interferometry are gratings, whose profile requirements play the most critical role in acquiring high quality images. The difficulty of etching grating lines with high aspect ratios when the pitch is in the range of a few micrometers has greatly limited imaging applications based on X-ray grating interferometry. A high etching rate with low aspect ratio dependence is crucial for higher X-ray energy applications and good profile control by deep reactive ion etching of grating patterns. To achieve this goal, a modified Coburn-Winters model was applied in order to study the influence of key etching parameters, such as chamber pressure and etching power. The recipe for deep reactive ion etching was carefully fine-tuned based on the experimental results. Silicon gratings with an area of 70 × 70 mm2, pitch size of 1.2 and 2 μm were fabricated using the optimized process with aspect ratio α of ~67 and 77, respectively.
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Affiliation(s)
- Zhitian Shi
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland; (K.J.); (L.R.); (M.S.)
- Department of Information Technology and Electrical Engineering, ETH Zürich, 8092 Zürich, Switzerland
| | - Konstantins Jefimovs
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland; (K.J.); (L.R.); (M.S.)
- Department of Information Technology and Electrical Engineering, ETH Zürich, 8092 Zürich, Switzerland
| | - Lucia Romano
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland; (K.J.); (L.R.); (M.S.)
- Department of Information Technology and Electrical Engineering, ETH Zürich, 8092 Zürich, Switzerland
- Department of Physics and CNR-IMM-University of Catania, 64 via S. Sofia, 95123 Catania, Italy
| | - Marco Stampanoni
- Paul Scherrer Institut, 5232 Villigen PSI, Switzerland; (K.J.); (L.R.); (M.S.)
- Department of Information Technology and Electrical Engineering, ETH Zürich, 8092 Zürich, Switzerland
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22
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Sensing Features of the Fano Resonance in an MIM Waveguide Coupled with an Elliptical Ring Resonant Cavity. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10155096] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In this article, a novel refractive index sensor composed of a metal–insulator–metal (MIM) waveguide with two rectangular stubs coupled with an elliptical ring resonator is proposed, the geometric parameters of which are controlled at a few hundreds of nanometer size. The transmission feature of the structure was studied by the finite element method based on electronic design automation (EDA) software COMSOL Multiphysics 5.4 (Stockholm, Sweden). The rectangular stub resonator can be thought of as a Fabry–Perot (FP) cavity, which can facilitate the Fano resonance. The simulation results reveal that the structure has a symmetric Lorentzian resonance, as well as an ultrasharp and asymmetrical Fano resonance. By adjusting the geometrical parameters, the sensitivity and figure of merit (FOM) of the structure can be optimized flexibly. After adjustments and optimization, the maximum sensitivity can reach up to 1550 nm/RIU (nanometer/Refractive Index Unit) and its FOM is 43.05. This structure presented in this article also has a promising application in highly integrated medical optical sensors to detect the concentration of hemoglobin and monitor body health.
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23
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Das D, Karmakar L. Autogenic single p/n-junction solar cells from black-Si nano-grass structures of p-to-n type self-converted electronic configuration. NANOSCALE 2020; 12:15371-15382. [PMID: 32656561 DOI: 10.1039/d0nr03927f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Photovoltaic performance of solar cells automatically improves when the absorber layer itself simultaneously acts as the anti-reflection nanostructure with an enhanced active absorber area on the front surface. Combined physical and chemical etching of p-c-Si wafers by (Ar + H2) plasma in inductively coupled low-pressure plasma CVD produces various nanostructures with subsequent minimization of reflectance. At a reduced temperature, the rate constant of thermal diffusion of atomic-H in the Si-network becomes smaller, leading to enhanced chemical etching reactions that further increase at an elevated RF power. Regrowth of the SiHn precursors produced by etching and subsequent hydrogenation in the plasma develops a high density of elongated nano-grass structures, which further align with sharp tips via Ar+ ion bombardment and elimination of loosely bound amorphous over-layers, on application of negative dc substrate bias during real-time etching and regrowth. A significantly reduced reflectance (∼0.5%) via coherent light trapping within the uniformly distributed vertically aligned nano-grass surfaces evolves truly black-silicon (b-Si) nanostructures, which further self-convert from the p-type to n-type electronic configuration via etching-mediated modification of B-H bonds from BH1 to BH2 and/or BH3 states, producing autogenic p/n junctions. Using (Ar + H2) plasma etched b-Si nano-grass structures at low temperature (∼200 °C), one-step fabrication of autogenic single p/n-junction proof-of-concept solar cells is accomplished. There is plenty of room for further progress in device performance.
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Affiliation(s)
- Debajyoti Das
- Energy Research Unit, School of Materials Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata - 700 032, India.
| | - Laxmikanta Karmakar
- Energy Research Unit, School of Materials Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata - 700 032, India.
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24
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Pandeshwar A, Kagias M, Wang Z, Stampanoni M. Modeling of beam hardening effects in a dual-phase X-ray grating interferometer for quantitative dark-field imaging. OPTICS EXPRESS 2020; 28:19187-19204. [PMID: 32672201 DOI: 10.1364/oe.395237] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 06/05/2020] [Indexed: 06/11/2023]
Abstract
X-ray grating interferometry (XGI) can provide access to unresolved sub-pixel information by utilizing the so-called dark-field or visibility reduction contrast. A recently developed variant of conventional XGI named dual-phase grating interferometer, based only on phase-shifting structures, has allowed for straightforward micro-structural investigations over multiple length scales with conventional X-ray sources. Nonetheless, the theoretical framework of the image formation for the dark-field signal has not been fully developed yet, thus hindering the quantification of unresolved micro-structures. In this work, we expand the current theoretical formulation of dual-phase grating interferometers taking into account polychromatic sources and beam hardening effects. We propose a model that considers the contribution of beam hardening to the visibility reduction and accounts for it. Finally, the method is applied to previously acquired and new experimental data showing that discrimination between actual micro-structures and beam hardening effects can be achieved.
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25
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Romano L, Stampanoni M. Microfabrication of X-ray Optics by Metal Assisted Chemical Etching: A Review. MICROMACHINES 2020; 11:E589. [PMID: 32545633 PMCID: PMC7344591 DOI: 10.3390/mi11060589] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 06/08/2020] [Accepted: 06/10/2020] [Indexed: 11/19/2022]
Abstract
High-aspect-ratio silicon micro- and nanostructures are technologically relevant in several applications, such as microelectronics, microelectromechanical systems, sensors, thermoelectric materials, battery anodes, solar cells, photonic devices, and X-ray optics. Microfabrication is usually achieved by dry-etch with reactive ions and KOH based wet-etch, metal assisted chemical etching (MacEtch) is emerging as a new etching technique that allows huge aspect ratio for feature size in the nanoscale. To date, a specialized review of MacEtch that considers both the fundamentals and X-ray optics applications is missing in the literature. This review aims to provide a comprehensive summary including: (i) fundamental mechanism; (ii) basics and roles to perform uniform etching in direction perpendicular to the <100> Si substrate; (iii) several examples of X-ray optics fabricated by MacEtch such as line gratings, circular gratings array, Fresnel zone plates, and other X-ray lenses; (iv) materials and methods for a full fabrication of absorbing gratings and the application in X-ray grating based interferometry; and (v) future perspectives of X-ray optics fabrication. The review provides researchers and engineers with an extensive and updated understanding of the principles and applications of MacEtch as a new technology for X-ray optics fabrication.
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Affiliation(s)
- Lucia Romano
- Institute for Biomedical Engineering, ETH Zürich, 8092 Zürich, Switzerland;
- Paul Scherrer Institut, Forschungsstrasse 111, CH-5232 Villigen, Switzerland
- CNR-IMM, Department of Physics, University of Catania, 64 via S. Sofia, 95123 Catania, Italy
| | - Marco Stampanoni
- Institute for Biomedical Engineering, ETH Zürich, 8092 Zürich, Switzerland;
- Paul Scherrer Institut, Forschungsstrasse 111, CH-5232 Villigen, Switzerland
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